ASTM D6994-15

Standard Test Method for Determination of Metal Cyanide Complexes in Wastewater, Surface Water, Groundwater and Drinking Water Using Anion Exchange Chromatography with UV Detection

SIGNIFICANCE AND USE
5.1 This method directly determines the concentration of metal cyanide complexes in environmental waters. The method is important from an environmental regulatory perspective because it differentiates metal cyanide complexes of lesser toxicity from metal cyanide complexes of greater toxicity. Previous determinations of strong metal cyanide complexes assumed that the concentration of strong metal cyanide complexes is equivalent to the difference between the total cyanide and the free cyanide. This approach is subject to error because different methods used to determine free cyanide often provide widely varying results, thus impacting the strong metal cyanide complex concentration that is determined by difference. The direct analysis using anion exchange chromatography avoids these method biases and provides for a more accurate and precise determination of metal cyanide complexes.
SCOPE
1.1 This test method covers the determination of the metal cyanide complexes of iron, cobalt, silver, gold, copper and nickel in waters including groundwaters, surface waters, drinking waters and wastewaters by anion exchange chromatography and UV detection. The use of alkaline sample preservation conditions (see 10.3) ensures that all metal cyanide complexes are solubilized and recovered in the analysis (1-3).2  
1.2 Metal cyanide complex concentrations between 0.20 to 200 mg/L may be determined by direct injection of the sample. This range will differ depending on the specific metal cyanide complex analyte, with some exhibiting greater or lesser detection sensitivity than others. Approximate concentration ranges are provided in 12.2. Concentrations greater than the specific analyte range may be determined after appropriate dilution. This test method is not applicable for matrices with high ionic strength (conductivity greater than 500 meq/L as Cl) and TDS (greater than 30 000 mg/L), such as ocean water.  
1.3 Metal cyanide complex concentrations less than 0.200 mg/L may be determined by on-line sample preconcentration coupled with anion exchange chromatography as described in 11.3. This range will differ depending on the specific metal cyanide complex analyte, with some exhibiting greater or lesser detection sensitivity than others. Approximate concentration ranges are provided in 12.2. The preconcentration method is not applicable for silver and copper cyanide complexes in matrices with high TDS (greater than 1000 mg/L).  
1.4 The test method may also be applied to the determination of additional metal cyanide complexes, such as those of platinum and palladium. However, it is the responsibility of the user of this standard to establish the validity of the test method for the determination of cyanide complexes of metals other than those in 1.1.  
1.5 The presence of metal complexes within a sample may be converted to Metal CN complexes and as such, are altered with the use of this method. This method is not applicable to samples that contain anionic complexes of metals that are weaker than cyanide complexes of those metals.  
1.6 The values stated in SI units are to be regarded as standard. The values given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not considered standard.  
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. For specific hazard statements, refer to Section 9.

General Information

• Status: Published
• Publication Date: 30-Sep-2015
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.05 - Inorganic Constituents in Water

Relations

• Replaces: ASTM D6994-10 - Standard Test Method for Determination of Metal Cyanide Complexes in Wastewater, Surface Water, Groundwater and Drinking Water Using Anion Exchange Chromatography with UV Detection
• Effective Date: 01-Oct-2015
• Refers: ASTM D6696-16(2023) - Standard Guide for Understanding Cyanide Species
• Effective Date: 15-Nov-2023
• Refers: ASTM D1129-13(2020)e2 - Standard Terminology Relating to Water
• Effective Date: 01-May-2020
• Refers: ASTM D6696-16 - Standard Guide for Understanding Cyanide Species
• Effective Date: 01-Apr-2016
• Refers: ASTM D6696-14 - Standard Guide for Understanding Cyanide Species
• Effective Date: 01-Jan-2014
• Refers: ASTM D2777-12 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jun-2012
• Refers: ASTM D3856-11 - Standard Guide for Management Systems in Laboratories Engaged in Analysis of Water
• Effective Date: 15-Nov-2011
• Refers: ASTM D5810-96(2011) - Standard Guide for Spiking into Aqueous Samples
• Effective Date: 01-May-2011
• Refers: ASTM D3370-10 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2010
• Refers: ASTM D6696-10 - Standard Guide for Understanding Cyanide Species
• Effective Date: 01-Jun-2010
• Refers: ASTM D1129-10 - Standard Terminology Relating to Water
• Effective Date: 01-Mar-2010
• Refers: ASTM D3370-08 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Oct-2008
• Refers: ASTM D2777-08 - Standard Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
• Effective Date: 15-Jan-2008
• Refers: ASTM D3370-07 - Standard Practices for Sampling Water from Closed Conduits
• Effective Date: 01-Dec-2007
• Refers: ASTM D1129-06ae1 - Standard Terminology Relating to Water
• Effective Date: 01-Sep-2006

Overview

ASTM D6994-15 is the standard test method for the determination of metal cyanide complexes in wastewater, surface water, groundwater, and drinking water using anion exchange chromatography with UV detection. This method provides a direct, accurate measurement of various metal-cyanide complexes - notably those of iron, cobalt, silver, gold, copper, and nickel - in a variety of environmental water samples. The standard plays a critical role in environmental monitoring and regulatory compliance, enabling laboratories and authorities to distinguish between metal cyanide complexes of differing toxicity.

Key Topics

• Direct Determination: Unlike indirect approaches, this method directly measures the concentration of metal-cyanide complexes, eliminating errors associated with subtractive calculations between total and free cyanide.
• Applicable Water Types: Suitable for groundwater, surface water, drinking water, and most wastewater. Not applicable to matrices with high ionic strength or total dissolved solids (e.g., ocean water).
• Analytical Range:
  • By direct injection: 0.20 to 200 mg/L (concentration may vary by analyte).
  • Using preconcentration: <0.200 mg/L (with certain limitations, especially for silver and copper at high TDS).
• Preservation: Samples must be collected and preserved under alkaline conditions (pH ≥ 12) to solubilize all metal-cyanide complexes and prevent degradation.
• Method Significance: The method’s ability to differentiate between strong and weak metal cyanide complexes is crucial for compliance and risk assessment, especially in regulated industries.
• Safety and Handling: Cyanides are highly toxic. The standard outlines necessary precautions for collection, sample handling, analysis, and waste disposal.

Applications

• Environmental Compliance: Used by regulatory authorities and environmental laboratories to enforce discharge limits of cyanide and metal cyanide complexes in industrial and municipal water systems.
• Water Quality Monitoring: Supports regular monitoring of drinking water, surface water, and groundwater resources for potentially harmful metal-cyanide pollutants.
• Industrial Wastewater Analysis: Essential for industries such as mining, electroplating, and metal finishing where cyanide complexes may be present in effluents.
• Risk Assessment: Provides vital data for toxicity differentiation among cyanide species, informing both public safety decisions and remediation plans.
• Research and Method Validation: Serves as a reference method in research studies and for validating other analytical methods targeting metal-cyanide complexes.

Related Standards

• ASTM D1129 - Terminology Relating to Water: Provides important definitions referenced in D6994-15.
• ASTM D1193 - Specification for Reagent Water: Specifies water purity requirements for reagent preparation and analysis.
• ASTM D3370 - Practices for Sampling Water: Details correct techniques for collecting representative water samples.
• ASTM D2777 - Practice for Determination of Precision and Bias: Assists in evaluating the analytical performance of the method.
• ASTM D6696 - Guide for Understanding Cyanide Species: Offers in-depth discussion of cyanide chemistry, including distinctions between free and complexed forms.
• ASTM D5847 - Practice for Writing Quality Control Specifications: Guides the design of quality assurance protocols in water analysis laboratories.

Summary

ASTM D6994-15 is a key standard for the direct measurement of metal cyanide complexes across a range of water types using anion exchange chromatography with UV detection. Its practical value lies in its accuracy, reliability, and suitability for regulatory, environmental, and industrial applications. By eliminating the ambiguities of previous methods and offering robust quality control and safety guidelines, ASTM D6994-15 ensures data integrity for informed decision-making in water quality management and environmental protection.

Keywords: ASTM D6994-15, metal cyanide complexes, anion exchange chromatography, UV detection, wastewater analysis, environmental water, regulatory compliance, water quality, cyanide monitoring, laboratory safety.

Standards Content (Sample)

This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: D6994 − 15
Standard Test Method for
Determination of Metal Cyanide Complexes in Wastewater,
Surface Water, Groundwater and Drinking Water Using
Anion Exchange Chromatography with UV Detection
This standard is issued under the fixed designation D6994; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope* 1.5 The presence of metal complexes within a sample may
be converted to Metal CN complexes and as such, are altered
1.1 This test method covers the determination of the metal
with the use of this method. This method is not applicable to
cyanide complexes of iron, cobalt, silver, gold, copper and
samples that contain anionic complexes of metals that are
nickelinwatersincludinggroundwaters,surfacewaters,drink-
weaker than cyanide complexes of those metals.
ing waters and wastewaters by anion exchange chromatogra-
phyandUVdetection.Theuseofalkalinesamplepreservation
1.6 The values stated in SI units are to be regarded as
conditions (see 10.3) ensures that all metal cyanide complexes
standard. The values given in parentheses are mathematical
are solubilized and recovered in the analysis (1-3).
conversions to inch-pound units that are provided for informa-
tion only and are not considered standard.
1.2 Metal cyanide complex concentrations between 0.20 to
200mg/Lmaybedeterminedbydirectinjectionofthesample.
1.7 This standard does not purport to address all of the
This range will differ depending on the specific metal cyanide
safety concerns, if any, associated with its use. It is the
complex analyte, with some exhibiting greater or lesser detec-
responsibility of the user of this standard to establish appro-
tion sensitivity than others.Approximate concentration ranges
priate safety, health, and environmental practices and deter-
are provided in 12.2. Concentrations greater than the specific
mine the applicability of regulatory limitations prior to use.
analyte range may be determined after appropriate dilution.
For specific hazard statements, refer to Section 9.
This test method is not applicable for matrices with high ionic
1.8 This international standard was developed in accor-
strength (conductivity greater than 500 meq/L as Cl) and TDS
dance with internationally recognized principles on standard-
(greater than 30000 mg/L), such as ocean water.
ization established in the Decision on Principles for the
Development of International Standards, Guides and Recom-
1.3 Metal cyanide complex concentrations less than 0.200
mendations issued by the World Trade Organization Technical
mg/L may be determined by on-line sample preconcentration
Barriers to Trade (TBT) Committee.
coupled with anion exchange chromatography as described in
11.3. This range will differ depending on the specific metal
2. Referenced Documents
cyanide complex analyte, with some exhibiting greater or
lesser detection sensitivity than others. Approximate concen-
2.1 ASTM Standards:
tration ranges are provided in 12.2. The preconcentration
D1129Terminology Relating to Water
method is not applicable for silver and copper cyanide com-
D1193Specification for Reagent Water
plexes in matrices with high TDS (greater than 1000 mg/L).
D2777Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
1.4 The test method may also be applied to the determina-
D3370Practices for Sampling Water from Closed Conduits
tion of additional metal cyanide complexes, such as those of
D3856Guide for Management Systems in Laboratories
platinumandpalladium.However,itistheresponsibilityofthe
Engaged in Analysis of Water
user of this standard to establish the validity of the test method
D5810Guide for Spiking into Aqueous Samples
for the determination of cyanide complexes of metals other
D5847Practice for Writing Quality Control Specifications
than those in 1.1.
for Standard Test Methods for Water Analysis
D6696Guide for Understanding Cyanide Species
This test method is under the jurisdiction of ASTM Committee D19 on Water
and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents
in Water.
Current edition approved Oct. 1, 2015. Published October 2015. Originally
approved in 2004. Last previous edition approved in 2010 as D6994–10. DOI: For referenced ASTM standards, visit the ASTM website, www.astm.org, or
10.1520/D6994-15. contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Theboldfacenumbersinparenthesesrefertothelistofreferencesattheendof Standards volume information, refer to the standard’s Document Summary page on
this standard. the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6994 − 15
3. Terminology are considered to be among the most stable and least toxic
forms of cyanide. Refer to Guide D6696 for a more detailed
3.1 Definitions:
discussion of aqueous cyanide species.
3.1.1 For a definition of terms used in this standard, refer to
3.2.9.3 Discussion—Themetalcyanidecomplexescanform
Terminology D1129.
saltswithavarietyofalkaliandtransitionmetalcations.These
3.2 Definitions of Terms Specific to This Standard:
alkali metal cyanide complex salts are soluble under alkaline
3.2.1 anion exchange chromatography, n—a type of liquid
conditions (1-3).
chromatography in which anionic analytes are separated by
3.2.10 free cyanide, n—the form of cyanide recognized as
differential retention on an anion exchange resin and detected
being bioavailable and toxic.
by an appropriate detection mechanism.
3.2.10.1 Discussion—Free cyanide may be present as either
3.2.2 eluent, n—the liquid mobile phase used in anion
molecular HCN or the anion CN- depending on the pH
exchange chromatography to transport the sample through the
conditions. Refer to Guide D6696 for a more detailed discus-
chromatography system.
sion of aqueous cyanide species.
3.2.3 analytical column, n—the chromatography column
4. Summary of Test Method
that contains the stationary phase for separation by ion ex-
change. 4.1 Dissolved metal cyanide complexes are determined by
anion exchange chromatography. For samples containing from
3.2.3.1 Discussion—The column is packed with anion ex-
0.2 to 200 mg/Lmetal cyanides a sample volume of 0.1 mLis
change resin that separates the analytes of interest based on
injected directly into the ion chromatograph where the metal
their retention characteristics prior to detection.
cyanide analytes are separated by being differentially retained
3.2.4 guardcolumn,n—ashortchromatographycolumnthat
on the anion exchange column (4). The concentration range
isplacedbeforetheanalyticalcolumntoprotectthelatterfrom
will differ depending on the specific metal cyanide analyte,
particulates and impurities that may cause fouling.
with some complexes exhibiting greater or lesser detection
3.2.5 anion trap column, n—a high-capacity, low-pressure
sensitivity than others based on their molar absorptivity. Refer
anion exchange column used to remove reagent impurities
to 12.2 for actual concentration ranges for individual metal
from the eluent stream.
cyanide complexes. The metal cyanide complexes are eluted
3.2.5.1 Discussion—The anion trap column is placed be-
from the column by the eluent gradient and detected as signal
tween the eluent reservoir and the gradient pump.
peaks using UV absorption at 215 nm. Their concentrations in
3.2.6 gradient elution, n—a type of elution in which the the sample are determined by comparison of the analyte peak
area with a standard calibration plot. Under the alkaline
eluent composition is steadily altered throughout the analysis
3-
inordertoprovideforanadequateseparationoftheanalytesof conditions of the analysis, ferricyanide ([Fe(CN) ] )isre-
4-
duced to ferrocyanide ([Fe(CN) ] ) (1, 2), yielding a single
interest prior to detection.
analyte peak.Any unreduced ferricyanide will be exhibited as
3.2.7 gradient pump, n—aliquidchromatographypumpthat
tailing on the ferrocyanide peak.
is capable of performing gradient elutions.
4.2 Forsamplescontainingfrom0.50to200µg/L,dissolved
3.2.8 total cyanide, n—the sum total of all of the inorganic
metal cyanide complexes are determined by using anion
chemical forms of cyanide.
exchange chromatography coupled with on-line sample pre-
3.2.8.1 Discussion—Total cyanide thus includes both free
concentration (4, 5).TwentymLofsampleispassedthroughan
cyanide and anionic metal cyanide complexes.
anion exchange concentrator column. As the sample passes
3.2.9 metal cyanide complex, n—a negatively charged ionic
through the column, the metal cyanide complexes are retained
complex consisting of one or more cyanide ions bound to a
and concentrated on the column while the remainder of the
single transition metal cation.
sample matrix is directed to waste. Following concentration,
3.2.9.1 Discussion—Also referred to as metal-complexed
the metal cyanide analytes are eluted from the concentrator
cyanides, these complexes have the general formula:
column through gradient elution, into the chromatograph and
x2
@M~CN! # (1) onto an anion exchange column where the remainder of the
b
analysisiscompletedasdescribedin4.1.Thecalibrationrange
where:
for metal cyanide complexes using sample preconcentration
M = transition metal cation,
method is between 0.50 to 200 µg/L. This range will differ
b = number of cyanide groups, and
depending on the specific metal cyanide analyte, with some
x = ionic charge of the transition metal complex.
complexes exhibiting greater or lesser detection sensitivity
than others based on their molar absorptivity. Refer to 12.2 for
3.2.9.2 Discussion—Metalcyanidecomplexesarerelatively
actual concentration ranges for individual metal cyanide com-
stableandrequiremoderatetohighlyacidicconditionsinorder
plexes.
to dissociate and form free cyanide. Based on their stability,
metal cyanide complexes are divided into two categories:
5. Significance and Use
“weak metal cyanide complexes” and “strong metal cyanide
complexes.” Examples of strong metal cyanide complexes 5.1 This method directly determines the concentration of
include the iron cyanide complexes prevalent in many cyanide metalcyanidecomplexesinenvironmentalwaters.Themethod
containingindustrialwastewaters.Theironcyanidecomplexes is important from an environmental regulatory perspective
D6994 − 15
because it differentiates metal cyanide complexes of lesser 6.5 Freemetalcationspresentineitherthesamplematrixor
toxicity from metal cyanide complexes of greater toxicity. as impurities in the combined eluent stream can combine with
Previous determinations of strong metal cyanide complexes the free cyanide present in Eluent 1 (see 8.12) to form
assumed that the concentration of strong metal cyanide com- extraneous metal cyanide complexes. Metal free trap columns
plexes is equivalent to the difference between the total cyanide should be installed to prevent positive interference by extrane-
and the free cyanide. This approach is subject to error because ous metal cyanide complexes during the low-level analysis
differentmethodsusedtodeterminefreecyanideoftenprovide procedure (see 7.2.5).
widelyvaryingresults,thusimpactingthestrongmetalcyanide
6.6 The method calibration for iron cyanide is based on its
complex concentration that is determined by difference. The
reduced form, ferrocyanide. Although the alkaline conditions
direct analysis using anion exchange chromatography avoids
of the analysis favor the reduction of ferricyanide to
these method biases and provides for a more accurate and
ferrocyanide, any unreduced species could potentially contrib-
precise determination of metal cyanide complexes.
ute to a bias in the analytical results.
6.7 Matrices with relatively high ionic strength or high total
6. Interferences
dissolved solids, for example, ocean water, will affect the
6.1 Photodecomposition of some metal cyanide complexes
performance of the analytical columns, resulting in poor
such as those of iron can reduce their concentration (6-8).
separation and recovery of the metal cyanide complexes.
Samples shall be collected so as to prevent exposure to light
6.8 When performing anion exchange chromatography
(see 10.2). Samples shall be analyzed in amber bottles and
coupled with on-line sample preconcentration, the silver and
protected from light whenever possible.
copper cyanide complexes exhibit reduced precision and in-
6.2 Carbonate is not a method interference but can accumu-
creased bias, especially in high ionic strength matrices, for
late by adherence to the anion exchange resin of the analytical
example, certain wastewaters. For the silver cyanide complex,
column. This may eventually lead to unstable baselines and a
large front-end tailing in samples containing high total dis-
reduction in column capacity and analyte retention. Care shall
solved solids affects peak resolution. For the copper and silver
betakentoavoidcarbonatecontaminationwhenpreparingand
cyanide complexes possible dissociation during the analysis
using sodium hydroxide eluents (9, 10).(Warning—
might also affect quantitation in samples containing high total
Carbonateisformedinsodiumhydroxidesolutionsbyreaction
dissolved solids.Any matrix with high ionic strength and total
with atmospheric carbon dioxide. Prepare all eluents using
dissolved solids (TDS > 1000 mg/L) could affect the perfor-
reagent water degassed by helium sparging or vacuum sonica-
mance of the analytical columns when performing sample
tion to prevent carbonate contamination as well as eluent
preconcentration, which may result in poor separation and
outgassing during the analysis. Guidelines are provided in the
recovery of metal cyanide complexes.
test method for preparing low-carbonate sodium hydroxide
eluent and reagent solutions (see Refs 9, 10).)
7. Apparatus
6.3 Commercial grade sodium cyanide used in the prepara-
7.1 Anion Exchange Chromatography Apparatus Require-
tion of Eluent 1 (see 8.12) often contains metal cyanide
ments:
compleximpurities.Theseimpuritiescancausenoisy,unstable
7.1.1 Pressurized Eluent Reservoir—Accessories must in-
baselinesduringthegradientelutionprofile.Theinstallationof
cludeagasregulatorcapableofmaintaininga13.8to68.9kPa
an anion trap column between the Eluent 1 reservoir and the
(2to10psi)headpressureontheeluentsolutionsusinghelium
gradient pump removes the impurities from the eluent stream
gas.
resulting in improved chromatographic baselines. Guidelines
7.1.2 Pressurizable Eluent Bottles—Bottlesmustbecapable
forpreparingandinstallingtheaniontrapcolumnareprovided
of withstanding an internal pressure of 51 to 68.9 kPa (7 to 10
in the test method (see 7.1.6 and 11.6).
psi). The bottles must be made of a chemically inert plastic
6.4 The IonPac AG5, AG11, AS5 and AS11 chromatogra-
suchaspolypropylene,suitableforusewithsodiumhydroxide-
phy columns referenced in the test method (see 7.1.7, 7.1.8,
based eluents.
and 7.2.4) are polymeric and accordingly will concentrate
7.1.3 Tubing—To be used with the eluent reservoir and
neutral organics and polyvalent organic anions at the head of
madeofamaterialthatiscompatiblewiththeeluentsolutions.
the column. Organic species containing a carbonate functional
7.1.4 GradientPump—Highperformanceliquidchromatog-
group will absorb at 215 nm. These species can potentially
raphy (HPLC) or ion chromatography (IC) pump capable of
cause “ghost” peaks when eluted during the analysis. This
delivering a constant flow in the range of 1 to 5 mL/min at a
effect is a function of the quality of the water used in the
pressure of 1379 to 13790 kPa (200 to 2000 psi).
preparation of the eluent solutions as well as the column
7.1.5 Chromatography Tubing—The tubing must be pres-
equilibration time. Sample preconcentration will enhance this
sureresistant(approximately20682kPa{3000psi})andmade
effect. High purity reagent water containing as low a concen-
of a material that is compatible with the eluent solutions.
tration as possible of organic contaminants should be used in
Examples of suitable materials are polyether ether ketone
the preparation of reagents (see 8.2).
(PEEK) and 316 stainless steel.
7.1.6 Anion Trap Column—The anion trap column is a low
pressure column that is placed between the Eluent 1 reservoir
A trademark by Dionex Corporation, Sunnyvale, CA. and the gradient pump inlet to trap and remove metal cyanide
D6994 − 15
impurities. The column is packed with a high-capacity anion 7.2.6 Sample Concentrator Pump—Liquid chromatography
exchangeresin.AnexampleofasuitablecolumnistheDionex or otherwise equivalent pump capable of interfacing with the
IonPac ATC-3 4-mm (9 by 24 mm) or equivalent (11). The instrument control and data collection system. The selected
column must be composed of a material appropriate for use sample pump must be capable of delivering a constant flow in
with sodium hydroxide eluents. the range of 1 to 5 mL/min at a pressure of 1379 to 13790 kPa
7.1.7 Analytical Column—Low-capacity anion exchange (200 to 2000 psi).
chromatography column. The selected column must provide
7.3 Plastic Volumetric Flasks—1000 mL and 100 mL.
for adequate selectivity of highly valent metal cyanide com-
7.4 Amber Reagent Bottles—1000 mL and 100 mL.
plexes. Examples include the Dionex IonPacAS5 (4-mm) and
the Dionex IonPac AS11 (4-mm or 2-mm) columns, or 7.5 Membrane Syringe Filters—25 mm diameter, 0.2 to
equivalent (9, 10). These columns differ somewhat in selectiv- 0.45µmporesize,havinglowbackgroundextractables,usedto
ity. The AS5 column provides greater selectivity for the early filter sample particulates.
eluting silver, copper and gold cyanide complexes while the
7.6 Plastic Syringes—5 and 10 mL volumes.
AS11 column provides greater selectivity for the iron cyanide
7.7 pH Electrode and Meter.
complex.The2-mmcolumnrequires ⁄4thesamplevolumeand
operates at ⁄4 the flowrate of a 4-mm column. Due to the
8. Reagents and Materials
decreased flowrate, the 2-mm column consumes only ⁄4 the
8.1 Purity of Reagents—Reagent grade chemicals must be
eluent required by a 4-mm column.
used in all tests. Unless otherwise indicated, it is intended that
7.1.8 Guard Column—Optional low-capacity anion ex-
all reagents shall conform to the specifications of the Commit-
change chromatography guard column. This column may be
teeonAnalyticalReagentsoftheAmericanChemicalSociety.
usedbeforetheanalyticalcolumntoremovesampleimpurities
andpreventthemfrompassingontotheanalyticalcolumn.The
8.2 Purity of Water—Unless otherwise indicated, references
selectedcolumnshallprovideforadequateselectivityofhighly
towatershallbeunderstoodtomeanreagentwaterconforming
valent metal cyanide complexes. Examples include the Dionex
to Specification D1193, Type I. It is recommended that special
IonPac AG5 and IonPac AG11 columns or equivalent (9, 10).
precautions such as routine contaminant monitoring and/or
7.1.9 UV/Vis Detector—Liquid chromatography UV/Vis
frequentreplacementofpolishingcartridgesbetakentoensure
detector, capable of low wavelength detection at 215 nm.
thatthetotalorganiccarboncontentofthewateris ≤100µg/L.
7.1.10 Instrument Control and Data Collection System—
This practice will limit the elution of organic species and
Standard equipment such as electronic control devices and
subsequent appearance of “ghost” peaks in the chromatograms
computer and software and/or integrators for providing auto-
(see 6.4). Figs. 1 and 2 provide examples of blank chromato-
matic control of the chromatography system, instrument cali-
grams.
bration and data analysis.
8.3 Degassed Reagent Water—Sparge reagent water with
7.2 On-line Sample Preconcentration Accessories—
heliumgasorsonicateundervacuumforapproximately20min
Additional electrical contact closures are required for estab-
to remove dissolved gases such as carbon dioxide.
lishing automatic control of the preconcentration hardware
8.4 Cobalt Cyanide Solution, Stock (1.00 mL = 1000 µg
accessories.
3-
[Co(CN) ] )—Dissolve exactly 1.5455 g of Potassium
7.2.1 Injection Valve—-way switching valve capable of
hexacyanocobaltate (III) (potassium cobalt cyanide),
injecting volumes ranging from 0.1 µL to 1 mL.
K [Co(CN) ], with 500 mL of Sodium Hydroxide Solution II
3 6
7.2.2 Autosampler—Capable of handling 40 mL sample
(see 8.34) in a 1000 mL volumetric flask. Dilute to volume
vials for use in performing sample preconcentration.
with Sodium Hydroxide Solution II (see 8.34) and store at
7.2.3 Large Sample Vials—40 mL amber glass vials. The
ambient temperature ina1L amber reagent bottle. The
use of self-sealing vials is recommended to prohibit exposure
solution is relatively stable and may be stored for up to one
ofthesampletolightduringandaftersampleinjectionsoasto
month.
prevent photodecomposition of some metal cyanide com-
8.5 Cobalt Cyanide I Solution, Standard (1.00 mL = 100 µg
plexes.
3- 3-
[Co(CN) ] )—Dilute exactly 10 mL of [Co(CN) ] Stock
6 6
7.2.4 Concentrator Column—Low-capacity anion exchange
Solution (see 8.4) to 100 mLwith Sodium Hydroxide Solution
chromatography concentrator column. The selected column
II (see 8.34). Store the solution in an amber reagent bottle.
shallprovideforadequateselectivityofhighlyvalenttransition
Prepare daily with analysis.
metal cyanide complexes. Examples are the Dionex IonPac
8.6 Cobalt Cyanide II Solution, Standard (1.00 mL = 10 µg
AG5 and IonPac AG11 columns or equivalent.
3- 3-
[Co(CN) ] )—Dilute exactly 10 mL of [Co(CN) ] Standard
7.2.5 Metal Free Trap Column (MFC)—Specially designed
6 6
Solution I (see 8.5) to 100 mL with Sodium Hydroxide
column for the on-line cleanup of eluent ionic transition metal
impurities.Twosuchcolumnsshouldbeinstalled;onebetween
the gradient pump outlet and the injection valve and the other
Reagent Chemicals, American Chemical Society Specifications,Am. Chemical
between the sample concentrator pump outlet and the injection
Soc., Washington, DC. For suggestions on the testing of reagents not listed by the
valve (see 7.2.1).An example is the Dionex IonPac MFC-1 or
AmericanChemicalSociety,see Analar Standards for Laboratory Chemicals,BDH
equivalent (12). Refer to the manufacturer’s instructions for
Ltd., Poole, Dorset, U.K., and the Unites States Pharmacopeia and National
column preparation and clean-up. Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.
D6994 − 15
FIG. 1 Blank Chromatogram of Reagent Water
FIG. 2 Blank Chromatogram of Reagent Water Using On-line Sample Preconcentration
Solution II (see 8.34). Store the solution in an amber reagent Solution (see 8.8) to 100 mLwith Sodium Hydroxide Solution
bottle. Prepare daily with analysis. II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
8.7 Cobalt Cyanide III Solution, Standard (1.00 mL = 0.1
3- 3-
µg [Co(CN) ] )—Dilute exactly 1 mL of [Co(CN) ] Stan-
6 6 8.10 Copper Cyanide II Solution, Standard (1.00 mL = 10
2- 2-
dard Solution II (see 8.6) to 100 mL with Sodium Hydroxide
µg [Cu(CN) ] )—Dilute exactly 10 mL of [Cu(CN) ] Stan-
3 3
Solution II (see 8.34). Store the solution in an amber reagent
dard Solution I (see 8.9) to 100 mL with Sodium Hydroxide
bottle. Prepare daily with analysis.
Solution II (see 8.34). Store the solution in an amber reagent
2-
8.8 CopperCyanide,Stock(1.00mL=1000µgCu[(CN) ]
bottle. Prepare daily with analysis.
)—Combine exactly 0.6325 g of Tricyanocuprate(I) (copper
8.11 Copper Cyanide III Solution, Standard (1.00 mL = 0.1
cyanide), CuCN, with 500 mL of Sodium Hydroxide Solution
2- 2-
µg [Cu(CN) ] )—Dilute exactly 1 mL of [Cu(CN) ] Stan-
3 3
II(see8.34)ina1000mLvolumetricflask.Addexactly1.3844
dard Solution II (see 8.10) to 100 mLwith Sodium Hydroxide
g of sodium cyanide, NaCN, and stir to dissolve both the
Solution II (see 8.34). Store the solution in an amber reagent
copper cyanide and sodium cyanide. Dilute to volume with
bottle. Prepare daily with analysis.
Sodium Hydroxide Solution II (see 8.34), mix it at least for an
hour and store at ambient temperature ina1L amber reagent
8.12 Eluent 1 (20 mM NaOH, 150 mM NaCN)—Place 1.6 g
bottle. Prepare daily with analysis. (Warning—NaCN is ex-
of Sodium Hydroxide Solution I (see 8.33) and 7.35 g of
tremely toxic. Avoid inhalation and skin and eye contact (see
sodium cyanide into a plastic 1 L volumetric flask. Add
9.1.1).) (Warning—The copper cyanide will dissolve upon
approximately 300 mL of degassed reagent water and swirl to
addition of sodium cyanide to form the tricyanocuprate(I)
dissolve. Dilute to volume with degassed reagent water and
2-
complex, [Cu(CN) ] that is the analyte of interest.)
mix thoroughly. The sodium cyanide is used to maintain the
integrity of the metal cyanide complexes throughout the
8.9 Copper Cyanide I Solution, Standard (1.00 mL= 100 µg
2- 2-
[Cu(CN) ] )—Dilute exactly 10 mL of [Cu(CN) ] Stock analysis.
3 3
D6994 − 15
8.13 Eluent 2 (20 mM NaOH, 300 mM NaClO ·H O)— 8.23 Iron Cyanide III Solution, Standard (1.00 mL = 0.1 µg
4 2
4- 4-
Place1.6gofSodiumHydroxideSolutionI(see8.33)and42.1 [Fe(CN) ] )—Dilute exactly 1 mL of [Fe(CN) ] Standard
6 6
g of sodium perchlorate monohydrate into a plastic 1 L Solution II (see 8.22) to 100 mL with Sodium Hydroxide
volumetric flask. Add approximately 300 mL of degassed Solution II (see 8.34). Store the solution in an amber reagent
reagent water and swirl to dissolve. Dilute to volume with bottle. Prepare daily with analysis.
degassed reagent water and mix thoroughly. The sodium
8.24 Nickel Cyanide Solution, Stock (1.00 mL = 1000 µg
perchlorate is used to elute the metal cyanide complexes from 2-
[Ni(CN) ] )—Dissolve exactly (1.4806 + 0.1107 × n)gof
the analytical column during the gradient elution.
Potassium tetracyanonickelate(II) (potassium nickel cyanide)
8.14 Eluent 3 (20 mM NaOH)—Place 1.6 g of Sodium mono-orpolyhydrate,K [Ni(CN) ]·nH2O(where, n=number
2 4
Hydroxide Solution I (see 8.33) into a plastic 1 L volumetric of water molecules of hydration), with 500 mL of Sodium
Hydroxide Solution II (see 8.34) in a 1000 mL volumetric
flask. Dilute to volume with degassed reagent water and mix
thoroughly. flask. Dilute to volume with Sodium Hydroxide Solution II
(see 8.34) and store at ambient temperature ina1L amber
8.15 Gold Cyanide Solution, Stock (1.00 mL = 1000 mg
reagent bottle. Prepare daily with analysis.
-
[Au(CN) ] )—Dissolve exactly 1.1570 g of Potassium dicya-
8.25 NickelCyanideISolution,Standard(1.00mL=100µg
noaurate(I)(potassiumgoldcyanide),KAu(CN) ,with500mL
2- 2-
[Ni(CN) ] )—Dilute exactly 10 mL of [Ni(CN) ] Stock
of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL
4 4
Solution (see 8.24) to 100 mL with Sodium Hydroxide
volumetric flask. Dilute to volume with Sodium Hydroxide
Solution II (see 8.34). Store the solution in an amber reagent
Solution II (see 8.34) and store at ambient temperature in a 1
bottle. Prepare daily with analysis.
L amber reagent bottle. The solution is relatively stable and
may be stored for up to one month.
8.26 Nickel Cyanide II Solution, Standard (1.00 mL= 10 µg
2- 2-
[Ni(CN) ] )—Dilute exactly 10 mL of [Ni(CN) ] Standard
8.16 Gold Cyanide I Solution, Standard (1.00 mL = 100 µg
4 4
- -
Solution I (see 8.25) to 100 mL with Sodium Hydroxide
[Au(CN) ] )—Dilute exactly 10 mL of [Au(CN) ] Stock So-
2 2
Solution II (see 8.34). Store the solution in an amber reagent
lution (see 8.15) to 100 mL with Sodium Hydroxide Solution
bottle. Prepare daily with analysis.
II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
8.27 Nickel Cyanide III Solution, Standard (1.00 mL = 0.1
2- 2-
µg [Ni(CN) ] )—Dilute exactly 1 mLof [Ni(CN) ] Standard
8.17 Gold Cyanide II Solution, Standard (1.00 mL = 10 µg 4 4
- -
Solution II (see 8.26) to 100 mL with Sodium Hydroxide
[Au(CN) ] )—Dilute exactly 10 mL of [Au(CN) ] Standard
2 2
Solution II (see 8.34). Store the solution in an amber reagent
Solution I (see 8.16) to 100 mL with Sodium Hydroxide
bottle. Prepare daily with analysis.
Solution II (see 8.34). Store the solution in an amber reagent
bottle. Prepare daily with analysis.
8.28 Reagent Blank—Use Sodium Hydroxide Solution II
(see 8.34).
8.18 Gold Cyanide III Solution, Standard (1.00 mL= 0.1 µg
- -
[Au(CN) ] )—Dilute exactly 1 mL of [Au(CN) ] Standard
8.29 Silver Cyanide Solution, Stock (1.00 mL = 1000 µg
2 2
-
Solution II (see 8.17) to 100 mL with Sodium Hydroxide
[Ag(CN) ] )—Dissolve exactly 1.2445 g of potassium dicya-
Solution II (see 8.34). Store the solution in an amber reagent
noargentate(I) (potassium silver cyanide), K[Ag(CN) ], with
bottle. Prepare daily with analysis.
500 mLof Sodium Hydroxide Solution II (see 8.34) in a 1000
mLvolumetricflask.DilutetovolumewithSodiumHydroxide
8.19 Helium Gas—Ultra high purity.
Solution II (see 8.34) and store at ambient temperature in a 1
8.20 Iron Cyanide Solution, Stock (1.00 mL = 1000 µg
L amber reagent bottle. Prepare daily with analysis.
4-
[Fe(CN) ] )—Dissolve exactly 1.9929 g of Potassium
8.30 Silver Cyanide I Solution, Standard (1.00 mL = 100 µg
hexacyanoferrate(III) (ferrocyanide trihydrate),
- -
[Ag(CN) ] )—Dilute exactly 10 mL of [Ag(CN) ] Stock So-
2 2
K [Fe(CN) ]·3H O, with 500 mL of Sodium Hydroxide Solu-
4 6 2
lution (see 8.29) to 100 mL with Sodium Hydroxide Solution
tion II (see 8.34) in a 1000 mL volumetric flask. Dilute to
II (see 8.34). Store the solution in an amber reagent bottle.
volume with Sodium Hydroxide Solution II (see 8.34) and
Prepare daily with analysis.
storeatambienttemperatureina1Lamberreagentbottle.The
solution is relatively stable and may be stored for up to one
8.31 Silver Cyanide II Solution, Standard (1.00 mL = 10 µg
- -
month.
[Ag(CN) ] )—Dilute exactly 10 mL of [Ag(CN) ] Standard
2 2
Solution I (see 8.30) to 100 mL with Sodium Hydroxide
8.21 Iron Cyanide I Solution, Standard (1.00 mL = 100 µg
4- 4- Solution II (see 8.34). Store the solution in an amber reagent
[Fe(CN) ] )—Dilute exactly 10 mL of [Fe(CN) ] Stock
6 6
bottle. Prepare daily with analysis.
Solution (see 8.20) to 100 mL with Sodium Hydroxide
Solution II (see 8.34). Store the solution in an amber reagent
8.32 Silver Cyanide III Solution, Standard (1.00 mL = 0.1
- -
bottle. Prepare daily with analysis. µg [Ag(CN) ] )—Dilute exactly 1 mL of [Ag(CN) ] Standard
2 2
Solution II (see 8.31) to 100 mL with Sodium Hydroxide
8.22 Iron Cyanide II Solution, Standard (1.00 mL = 10 µg
4- 4- Solution II (see 8.34). Store the solution in an amber reagent
[Fe(CN) ] )—Dilute exactly 10 mL of [Fe(CN) ] Standard
6 6
bottle. Prepare daily with analysis.
Solution I (see 8.21) to 100 mL with Sodium Hydroxide
Solution II (see 8.34). Store the solution in an amber reagent 8.33 Sodium Hydroxide Solution I (50 % w⁄w)—It is rec-
bottle. Prepare daily with analysis. ommended that the solution be purchased from a vendor so as
D6994 − 15
to have the lowest possible carbonate contamination.Attempts 11.2 Set up the method by programming the instrument
to prepare the solution manually may result in carbonate control and data collection system or the gradient pump
contamination. (Warning—This solution is only used for the directly to perform gradient elution anion chromatography
preparation of reagents and is not a reagent itself.) analysis of metal cyanide complexes as specified in Table 1.
Portions of the analysis program, such as the gradient elution
8.34 Sodium Hydroxide Solution II (10 mM, pH = 12)—
conditions, may be modified as appropriate provided the
Place 0.8 g of Sodium Hydroxide Solution I (see 8.33) into a
analytical results fall within the precision and bias established
plastic 1 L volumetric flask. Dilute to volume with degassed
for the test method (see Section 15).
reagent water and mix thoroughly. Check to ensure that the pH
11.3 Anion Exchange Chromatography Analysis Using On-
is ≥ 12 using pH paper or a calibrated pH electrode. Add
line Sample Preconcentration—Analyze samples containing
additionalSodiumHydroxideSolutionI,ifneeded,tobringthe
less than 0.20 mg/Lmetal cyanide complexes by using on-line
pH to 12. This solution is used in the preparation of all
sample preconcentration prior to anion exchange chromatog-
standards in order to match the matrix of the standards to that
raphy analysis.
ofthealkalinepreservedsamples.Inaddition,thehighpHacts
11.3.1 Set up the chromatography hardware for performing
as a safety measure to prevent formation of gaseous HCN in
analysis with initial on-line sample preconcentration. An ex-
the event of decomposition of the metal cyanide complex
standards. ampleofasuitablehardwareconfigurationusingthemethodis
displayed in Figs. 4 and 5.
8.35 Filter Paper—Purchase suitable filter paper. Typically
11.3.2 Condition the MFCs per the manufacturer’s instruc-
the filter papers have a pore size of 0.45-µm membrane.
tions and install as shown in Fig. 4.
Material such as fine-textured, ashless paper, or glass fiber
11.3.3 Set the sample concentrator pump for a flow rate of
paperareacceptable.Theusermustfirstascertainthatthefilter
2 mL/min.
paper is of sufficient purity to use without adversely affecting
11.3.4 Prime the sample concentrator pump to remove
the bias and precision of the test method.
trapped air. Disconnect the tubing from the pump head and
withdraw eluent using a plastic syringe until no air bubbles are
9. Hazards
observed. Reconnect the tubing when finished. (Warning—
9.1 Safety Precautions:
The effluent from the chromatograph will contain cyanide and
9.1.1 Because of the toxicity of cyanide, exercise great care
should be handled and disposed of properly. See 9.1.2.)
in its handling. Acidification of cyanide solutions produces
11.4 Prime the gradient pump to remove trapped air within
lethal, toxic hydrogen cyanide (HCN) gas. Prepare all cyanide
eacheluentlineseparately.Selectoneeluent,setto100%,and
containing solutions within a ventilation hood. Wear hand and
begin priming. Repeat this step for the remaining eluents.
eye protection at all times when working with cyanide.
9.1.2 Someofthereagentsandsolutionsusedinthismethod
11.5 Prime the gradient pump once more using the initial
contain cyanide. Dispose of these materials properly. The method settings.
effluent from the chromatograph will contain cyanide. The
11.6 Condition the anion trap column according to the
effluent shall be collected and immediately adjusted to a pH of
manufacturer’s instructions.
12 or greater. Dispose of the effluent properly.
11.6.1 Connect the anion trap column directly to the outlet
of the gradient pump. Set the pump to 100% Eluent 1 (see
10. Sampling and Sample Preservation
8.12) and pump this through the column at 1 mL/min for 60
10.1 Collect the sample in accordance with Practices
min to convert the resin from the hydroxide to the cyanide
D3370.
form.Attheendofthetimeperiod,stopthegradientpumpand
disconnect the anion trap column from the outlet of the
10.2 Samples must be collected in polyethylene containers
covered in aluminum foil or otherwise equivalent containers gradient pump. Dispose of the contents of the waste beaker as
hazardous waste.
suchasthosecomposedofamberplasticsoastofilterUVlight
at 300 nm and below and prevent photodecomposition of iron 11.6.2 Place the conditioned anion trap column between the
Eluent 1 reservoir and the gradient pump inlet as shown in
and cobalt cyanide complexes.
Figs.3and4.(Warning—Theaniontrapcolumniscapableof
10.3 Samples for metal cyanide complex analysis must be
treating only a limited amount of Eluent 1. For optimum
preserved under alkaline conditions by adjusting the pH to 12
performance, the column must be reconditioned at a minimum
or greater using sodium hydroxide.
following treatment of each 2 to 3 L of Eluent 1.)
10.4 Store samples at 4°C for no longer than 14 days.
11.7 Reprime the Eluent 1 gradient pump line.
Samplesshallbebroughttoroomtemperaturepriortoanalysis.
11.8 Connect the guard and analytical columns between the
11. Preparation of Apparatus
injectionvalveandtheinletoftheUV/Visdetector.Ensurethat
the columns are oriented in the appropriate direction for eluent
11.1 Anion Exchange Chromatography Analysis—Analyze
flow.
samples containing greater than 0.20 mg/L metal cyanide
complexes by direct injection of 0.1 mL of sample. 11.9 Allow the instrument to equilibrate for at least 10 min
11.1.1 Set up the chromatography hardware in an appropri- prior to the analysis by pumping eluent through the concen-
ate manner for analysis. An example of a suitable hardware trator column (if present), guard and analytical columns at a
configuration using the method is displayed in Fig. 3. flow rate of 1 mL/min using the initial eluent settings.
D6994 − 15
FIG. 3 Chromatograph Configuration for the Analysis of Metal Cyanides
TABLE 1 Method Settings for the Analysis of Metal Cyanides Using Gradient Elution
Gradient Pump Absorbance Detector
Comments
Time
Flow Rate Eluent 1 Eluent 2 Eluent 3 Wavelength Data Collection
and Function
(mL/min) (%) (%) (%) (nm) (Absorbance Units)
Init. 1.00 10 10 80 215 Initial Conditions
0.0 1.00 10 10 80 215 Offset baseline Analysis Gradient
18.0 1.00 10 45 45 215 Begin
22.0 1.00 10 45 45 215 End
A
25.0 1.00 10 10 80 215 Equilibration
35.0 1.00 10 10 80 215
A
The eluents are reset to their initial concentrations and allowed to pump for 10 min at the end of the analysis run to equilibrate the columns prior to the next sample
injection.
TABLE 2 Method Settings for the Analysis of Metal Cyanides Using Gradient Elution and On-line Sample Preconcentration
Two-way Sample
Gradient Pump Absorbance Detector
Switching Enrichment Comments
Time
Flow Rate Eluent 1 Eluent 2 Eluent 3 Wavelength Data Collection
Valve Pump and Function
(mL/min) (%) (%) (%) (nm) (Absorbance Units)
Position (2 mL/min)
Init. Load 1.00 10 10 80 215 Initial Conditions
0.0 Load 1.00 10 10 80 215
A
1.0 Load 1.00 10 10 80 215 On Equilibration
11.0 Inject 1.00 10 10 80 215 Off Sample Injection
11.1 Inject 1.00 10 10 80 215 Offset baseline Analysis Gradient
11.2 Inject 1.00 10 10 80 215 Begin
29.2 Inject 1.00 10 45 45 215
33.2 Load 1.00 10 45 45 215 End
A
The eluents are pumped through the guard and analytical columns at their initial concentrations for 10 min at the beginning of the analysis run to equilibrate the columns
between sample injections. During this time, the sample concentrator pump is turned on and 20 mL of sample is pumped to the concentrator column.
11.10 Set the UV/Vis detector to 215 nm and offset the concentrator column by placing the injection valve in the
absorbance to zero. (Warning—Eluent is pumped through the “Inject” mode (see Fig. 5).)
D6994 − 15
FIG. 4 Chromatograph Configuration for the Analysis of Metal Cyanides Using Sample Preconcentration
FIG. 5 Injection Valve Configuration for Sample Preconcentration
12. Calibration 12.2 Prepare calibration standards so as to bracket the
calibration ranges of each of the metal cyanide complexes by
12.1 (Warning—Since all iron cyanide complexes are de-
4-
adding measured volumes of the metal cyanide standards (see
tected as ferrocyanide ([Fe(CN) ] ), this form of iron cyanide
Section8)tovolumetricflasks.Approximatecalibrationranges
is used in the preparation of the calibration standards.)
D6994 − 15
TABLE 3 Approximate Calibration Ranges for Metal Cyanide TABLE 4 Approximate Calibration Ranges for Metal Cyanide
Complexes Determined by Anion Exchange Chromatography Complexes Determined by Anion Exchange Chromatography
Using On-line Sample Preconcentration
Calibration Range
Cyanide Complex
(mg/L)
Calibration Range
Cyanide Complex
- (µg/L)
[Ag(CN) ] 0.5 to 100
-
-
[Au(CN) ] 0.2to50
2 [Ag(CN) ] 10 to 120
3-
-
[Co(CN) ] 0.5 to 100
[Au(CN) ] 5to100
2-
3-
[Cu(CN) ] 0.2to2.0
[Co(CN) ] 1.0 to 200
3 6
4-
2-
[Fe(CN) ] 0.10 to 20 [Cu(CN) ] 1.0to5.0
2-
4-
[Ni(CN) ] 1.0 to 200
[Fe(CN) ] 0.5to20
2-
[Ni(CN) ] 50 to 100
foreachmetalcyanidecomplexareprovidedinTables3and4.
Dilute the standards to their respective final volumes using
regression plot from 12.3. Make the necessary adjustments to
SodiumHydroxideSolutionII(see8.34).Prepareatleastthree
the final results based on any dilutions that were performed
standards or as otherwise required for regulatory reporting.
using the following calculation:
Store the standards in amber reagent bottles.
µgormg
x2
12.3 To establish the calibration curves, analyze the reagent
@M~CN! # 5 (2)
b
L
blank and calibration standards in accordance with the proce-
dure in Section 13. Plot calibration curves of peak area
µgormg mLfinaldilutionvolume
x2
@M~CN! # indilutedsample 3
response versus analyte concentration for each metal cyanide
b
L mLasreceivedsample
usingthereagentblankpeakareaintegrationforthezeropoint.
where:
Perform regressions of the plots. The correlation coefficient of
M = transition metal cation,
each regression should be 0.995 or greater for accurate results.
b = number of cyanide groups, and
Asecondorderregressionplotmaybeusedifneeded.Oncethe
x = ionic charge of the transition metal complex.
calibration curve has been established, verification must be
performed on each analysis day, whenever fresh eluent is
14.2 Convert the metal cyanide results to cyanide when
prepared and once per analysis batch as outlined in 16.3 and
reporting the results “as cyanide” based on the following
16.4.(Warning—The calibration and subsequent analysis
calculation:
results for iron cyanide should be presented as either
µgormg
x- 3-/4-
x2 2
[Fe(CN) ] or[Fe(CN) ] soastorepresentthetotalsumof M CN as CN 5 (3)
@ ~ ! #
6 6
b
L
ferrocyanide and ferricyanide.)
µgormg FormulaWt.of CN
~ !
x2
13. Procedure
@M~CN! # 3 ~b! 3
b x2
L ~FormulaWt.of @M~CN! # !
b
13.1 Filter an appropriate volume of sample using a plastic
Theformulaweightsforcyanideaswellasthoseforeachof
syringe fitted with a 0.45 µm syringe filter (8.35).
the metal cyanide complexes are provided in Table 5.
13.2 Transfer the filtered sample to an amber sample vial.
Repeat this procedure for the remaining samples.
15. Precision and Bias
13.3 Transfer the reagent blank, calibration standards and
15.1 Theprecisionandbiasforthistestmethodconformsto
QA/QC samples (see Section 16) and standards to amber
Practice D2777 – 98, which was in place at the time of
sample vials.
collaborative testing. Under the allowances made in 1.4 of
Practice D2777 – 13, these precision and bias data do meet
13.4 Place all of the vials in the autosampler.
existing requirements for interlaboratory studies of Committee
13.5 Start the autosampler and instrument control and data
D19 test methods.
collection system, if applicable, and begin analyzing the
15.2 The interlaboratory study that generated the precision
samples. A water blank should be analyzed first to equilibrate
and bias data in this test method for analysis of both mg/L
the columns followed by the reagent blank, calibration stan-
(ppm-level) metal cyanide complex concentrations (using an-
dards (see Section 12) and samples, including QA/QC samples
ion exchange chromatography-UV detection) (see 4.1) and
(see Section 16). Use an injection volume of 0.1 mL for
µg/L (ppb-level) metal cyanide complex concentrations (using
samplescontainingfrom0.200to200mg/Lmetalcyanidesand
anion exchange chromatography-UV detection with on-line
an injection volume of 20 mL when using sample preconcen-
sample preconcentration) (see 4.2) was performed in reagent
tration for samples containing from 0.50 to 200 µg/L. metal
water, wastewater, drinking water, surface water and ground-
cyanides. Periodically analyze a continuing calibration verifi-
water. The ppm-level analysis was performed by eight labora-
cation standard to assess instrument drift throughout the run
tories using a single operator at each lab. The ppb-level
(see 16.3 and 16.4). Examples of method chromatograms are
analysis was performed by seven laboratories using a single
provided in Figs. 6-9.
14. Calculation
Supporting data have been filed atASTM International Headquarters and may
14.1 Derive the concentration of each respective metal
beobtainedb
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D6994 − 10 D6994 − 15
Standard Test Method for
Determination of Metal Cyanide Complexes in Wastewater,
Surface Water, Groundwater and Drinking Water Using
Anion Exchange Chromatography with UV Detection
This standard is issued under the fixed designation D6994; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope*
1.1 This test method covers the determination of the metal cyanide complexes of iron, cobalt, silver, gold, copper and nickel
in waters including groundwaters, surface waters, drinking waters and wastewaters by anion exchange chromatography and UV
detection. The use of alkaline sample preservation conditions (see 10.3) ensures that all metal cyanide complexes are solubilized
and recovered in the analysis (1-3).
1.2 Metal cyanide complex concentrations between 0.20 to 200 mg/L may be determined by direct injection of the sample. This
range will differ depending on the specific metal cyanide complex analyte, with some exhibiting greater or lesser detection
sensitivity than others. Approximate concentration ranges are provided in 12.112.2. Concentrations greater than the specific analyte
range may be determined after appropriate dilution. This test method is not applicable for matrices with high ionic strength
(conductivity greater than 500 meq/L as Cl) and TDS (greater than 30 000 mg/L), such as ocean water.
1.3 Metal cyanide complex concentrations less than 0.200 mg/L may be determined by on-line sample preconcentration coupled
with anion exchange chromatography as described in 11.3. This range will differ depending on the specific metal cyanide complex
analyte, with some exhibiting greater or lesser detection sensitivity than others. Approximate concentration ranges are provided
in 12.112.2. The preconcentration method is not applicable for silver and copper cyanide complexes in matrices with high TDS
(greater than 1000 mg/L).
1.4 The test method may also be applied to the determination of additional metal cyanide complexes, such as those of platinum
and palladium. However, it is the responsibility of the user of this standard to establish the validity of the test method for the
determination of cyanide complexes of metals other than those in 1.1.
1.5 The presence of metal complexes within a sample may be converted to Metal CN complexes and as such, are altered with
the use of this method. This method is not applicable to samples that contain anionic complexes of metals that are weaker than
cyanide complexes of those metals.
1.6 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this The values
given in parentheses are mathematical conversions to inch-pound units that are provided for information only and are not
considered standard.
1.7 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use. For specific hazard statements, refer to Section 9.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.05 on Inorganic Constituents in Water.
Current edition approved Sept. 15, 2010Oct. 1, 2015. Published November 2010October 2015. Originally approved in 2004. Last previous edition approved in 20042010
as D6994 – 04.D6994 – 10. DOI: 10.1520/D6994-10.10.1520/D6994-15.
The boldface numbers in parentheses refer to the list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D6994 − 15
D3370 Practices for Sampling Water from Closed Conduits
D3856 Guide for Management Systems in Laboratories Engaged in Analysis of Water
D5810 Guide for Spiking into Aqueous Samples
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
D6696 Guide for Understanding Cyanide Species
3. Terminology
3.1 Definitions—Definitions: For a definition of terms used in this method, refer to Terminology D1129.
3.1.1 For a definition of terms used in this standard, refer to Terminology D1129.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 anion exchange chromatography, n—a type of liquid chromatography in which anionic analytes are separated by
differential retention on an anion exchange resin and detected by an appropriate detection mechanism.
3.2.2 eluent, n—the liquid mobile phase used in anion exchange chromatography to transport the sample through the
chromatography system.
3.2.3 analytical column, n—the chromatography column that contains the stationary phase for separation by ion exchange.
3.2.3.1 Discussion—
The column is packed with anion exchange resin that separates the analytes of interest based on their retention characteristics prior
to detection.
3.2.4 guard column, n—a short chromatography column that is placed before the analytical column to protect the latter from
particulates and impurities that may cause fouling.
3.2.5 anion trap column, n—a high-capacity, low-pressure anion exchange column used to remove reagent impurities from the
eluent stream.
3.2.5.1 Discussion—
The anion trap column is placed between the eluent reservoir and the gradient pump.
3.2.6 gradient elution, n—a type of elution in which the eluent composition is steadily altered throughout the analysis in order
to provide for an adequate separation of the analytes of interest prior to detection.
3.2.7 gradient pump, n—a liquid chromatography pump that is capable of performing gradient elutions.
3.2.8 total cyanide, n—the sum total of all of the inorganic chemical forms of cyanide.
3.2.8.1 Discussion—
Total cyanide thus includes both free cyanide and anionic metal cyanide complexes.
3.2.9 metal cyanide complex, n—a negatively charged ionic complex consisting of one or more cyanide ions bound to a single
transition metal cation.
3.2.9.1 Discussion—
Also referred to as metal-complexed cyanides, these complexes have the general formula:
x2
M CN (1)
@ ~ ! #
b
where:
M = transition metal cation,
b = number of cyanide groups, and
x = ionic charge of the transition metal complex.
3.2.9.2 Discussion—
Metal cyanide complexes are relatively stable and require moderate to highly acidic conditions in order to dissociate and form free
cyanide. Based on their stability, metal cyanide complexes are divided into two categories: “weak metal cyanide complexes” and
“strong metal cyanide complexes.” Examples of strong metal cyanide complexes include the iron cyanide complexes prevalent in
D6994 − 15
many cyanide containing industrial wastewaters. The iron cyanide complexes are considered to be among the most stable and least
toxic forms of cyanide. Refer to Guide D6696 for a more detailed discussion of aqueous cyanide species.
3.2.9.3 Discussion—
The metal cyanide complexes can form salts with a variety of alkali and transition metal cations. These alkali metal cyanide
complex salts are soluble under alkaline conditions (1-3).
3.2.10 free cyanide, n—the form of cyanide recognized as being bioavailable and toxic.
3.2.10.1 Discussion—
Free cyanide may be present as either molecular HCN or the anion CN- depending on the pH conditions. Refer to Guide D6696
for a more detailed discussion of aqueous cyanide species.
4. Summary of Test MethodsMethod
4.1 Dissolved metal cyanide complexes are determined by anion exchange chromatography. For samples containing from 0.2
to 200 mg/L metal cyanides a sample volume of 0.1 mL is injected directly into the ion chromatograph where the metal cyanide
analytes are separated by being differentially retained on the anion exchange column (4). The concentration range will differ
depending on the specific metal cyanide analyte, with some complexes exhibiting greater or lesser detection sensitivity than others
based on their molar absorptivity. Refer to 12.112.2 for actual concentration ranges for individual metal cyanide complexes. The
metal cyanide complexes are eluted from the column by the eluent gradient and detected as signal peaks using UV absorption at
215 nm. Their concentrations in the sample are determined by comparison of the analyte peak area with a standard calibration plot.
3- 4-
Under the alkaline conditions of the analysis, ferricyanide ([Fe(CN) ] ) is reduced to ferrocyanide ([Fe(CN) ] ) (1, 2), yielding
6 6
a single analyte peak. Any unreduced ferricyanide will be exhibited as tailing on the ferrocyanide peak.
4.2 For samples containing from 0.50 to 200 μg/L, dissolved metal cyanide complexes are determined by using anion exchange
chromatography coupled with on-line sample preconcentration (4, 5). Twenty mL of sample is passed through an anion exchange
concentrator column. As the sample passes through the column, the metal cyanide complexes are retained and concentrated on the
column while the remainder of the sample matrix is directed to waste. Following concentration, the metal cyanide analytes are
eluted from the concentrator column through gradient elution, into the chromatograph and onto an anion exchange column where
the remainder of the analysis is completed as described in 4.1. The calibration range for metal cyanide complexes using sample
preconcentration method is between 0.50 to 200 μg/L. This range will differ depending on the specific metal cyanide analyte, with
some complexes exhibiting greater or lesser detection sensitivity than others based on their molar absorptivity. Refer to 12.112.2
for actual concentration ranges for individual metal cyanide complexes.
5. Significance and Use
5.1 This method directly determines the concentration of metal cyanide complexes in environmental waters. The method is
important from an environmental regulatory perspective because it differentiates metal cyanide complexes of lesser toxicity from
metal cyanide complexes of greater toxicity. Previous determinations of strong metal cyanide complexes assumed that the
concentration of strong metal cyanide complexes is equivalent to the difference between the total cyanide and the free cyanide.
This approach is subject to error because different methods used to determine free cyanide often provide widely varying results,
thus impacting the strong metal cyanide complex concentration that is determined by difference. The direct analysis using anion
exchange chromatography avoids these method biases and provides for a more accurate and precise determination of metal cyanide
complexes.
6. Interferences
6.1 Photodecomposition of some metal cyanide complexes such as those of iron can reduce their concentration (6-8). Samples
shall be collected so as to prevent exposure to light (see 10.2). Samples shall be analyzed in amber bottles and protected from light
whenever possible.
6.2 Carbonate is not a method interference but can accumulate by adherence to the anion exchange resin of the analytical
column. This may eventually lead to unstable baselines and a reduction in column capacity and analyte retention. Care shall be
taken to avoid carbonate contamination when preparing and using sodium hydroxide eluents (9, 10). (Warning—Carbonate is
formed in sodium hydroxide solutions by reaction with atmospheric carbon dioxide. Prepare all eluents using reagent water
degassed by helium sparging or vacuum sonication to prevent carbonate contamination as well as eluent outgassing during the
analysis. Guidelines are provided in the test method for preparing low-carbonate sodium hydroxide eluent and reagent solutions
(see Refs 9, 10).)
NOTE 1—Caution: Carbonate is formed in sodium hydroxide solutions by reaction with atmospheric carbon dioxide. Prepare all eluents using reagent
D6994 − 15
water degassed by helium sparging or vacuum sonication to prevent carbonate contamination as well as eluent outgassing during the analysis. Guidelines
are provided in the test method for preparing low-carbonate sodium hydroxide eluent and reagent solutions (see Refs 9,10).
6.3 Commercial grade sodium cyanide used in the preparation of Eluent 1 (see 8.12) often contains metal cyanide complex
impurities. These impurities can cause noisy, unstable baselines during the gradient elution profile. The installation of an anion trap
column between the Eluent 1 reservoir and the gradient pump removes the impurities from the eluent stream resulting in improved
chromatographic baselines. Guidelines for preparing and installing the anion trap column are provided in the test method (see 7.1.6
and 11.6).
6.4 The IonPac®IonPac AG5, AG11, AS5 and AS11 chromatography columns referenced in the test method (see 7.1.7, 7.1.8,
and 7.2.4) are polymeric and accordingly will concentrate neutral organics and polyvalent organic anions at the head of the column.
Organic species containing a carbonate functional group will absorb at 215 nm. These species can potentially cause “ghost” peaks
when eluted during the analysis. This effect is a function of the quality of the water used in the preparation of the eluent solutions
as well as the column equilibration time. Sample preconcentration will enhance this effect. High purity reagent water containing
as low a concentration as possible of organic contaminants should be used in the preparation of reagents (see 8.2).
6.5 Free metal cations present in either the sample matrix or as impurities in the combined eluent stream can combine with the
free cyanide present in Eluent 1 (see 8.12) to form extraneous metal cyanide complexes. Metal free trap columns should be
installed to prevent positive interference by extraneous metal cyanide complexes during the low-level analysis procedure (see
7.2.5).
6.6 The method calibration for iron cyanide is based on its reduced form, ferrocyanide. Although the alkaline conditions of the
analysis favor the reduction of ferricyanide to ferrocyanide, any unreduced species could potentially contribute to a bias in the
analytical results.
6.7 Matrices with relatively high ionic strength or high total dissolved solids, for example, ocean water, will affect the
performance of the analytical columns, resulting in poor separation and recovery of the metal cyanide complexes.
6.8 When performing anion exchange chromatography coupled with on-line sample preconcentration, the silver and copper
cyanide complexes exhibit reduced precision and increased bias, especially in high ionic strength matrices, for example, certain
wastewaters. For the silver cyanide complex, large front-end tailing in samples containing high total dissolved solids affects peak
resolution. For the copper and silver cyanide complexes possible dissociation during the analysis might also affect quantitation in
samples containing high total dissolved solids. Any matrix with high ionic strength and total dissolved solids (TDS > 1000 mg/L)
could affect the performance of the analytical columns when performing sample preconcentration, which may result in poor
separation and recovery of metal cyanide complexes.
7. Apparatus
7.1 Anion Exchange Chromatography Apparatus Requirements:
7.1.1 Pressurized Eluent Reservoir—Accessories must include a gas regulator capable of maintaining a 2 to 10 psi13.8 to 68.9
kPa (2 to 10 psi) head pressure on the eluent solutions using helium gas.
7.1.2 Pressurizable Eluent Bottles—Bottles must be capable of withstanding an internal pressure of 7 to 10 psi.51 to 68.9 kPa
(7 to 10 psi). The bottles must be made of a chemically inert plastic such as polypropylene, suitable for use with sodium
hydroxide-based eluents.
7.1.3 Tubing—To be used with the eluent reservoir and made of a material that is compatible with the eluent solutions.
7.1.4 Gradient Pump—High performance liquid chromatography (HPLC) or ion chromatography (IC) pump capable of
delivering a constant flow in the range of 1 to 5 mL/min at a pressure of 200 to 2000 psi.1379 to 13790 kPa (200 to 2000 psi).
7.1.5 Chromatography Tubing—The tubing must be pressure resistant (approximately 3000 psi) 20682 kPa {3000 psi}) and
made of a material that is compatible with the eluent solutions. Examples of suitable materials are PEEK polyether ether ketone
(PEEK) and 316 stainless steel.
7.1.6 Anion Trap Column—The anion trap column is a low pressure column that is placed between the Eluent 1 reservoir and
the gradient pump inlet to trap and remove metal cyanide impurities. The column is packed with a high-capacity anion exchange
resin. An example of a suitable column is the Dionex IonPac ATC-3 4-mm (9 by 24 mm) or equivalent (11). The column must be
composed of a material appropriate for use with sodium hydroxide eluents.
7.1.7 Analytical Column—Low-capacity anion exchange chromatography column. The selected column must provide for
adequate selectivity of highly valent metal cyanide complexes. Examples include the Dionex IonPac AS5 (4-mm) and the Dionex
IonPac AS11 (4-mm or 2-mm) columns, or equivalent (9, 10). These columns differ somewhat in selectivity. The AS5 column
provides greater selectivity for the early eluting silver, copper and gold cyanide complexes while the AS11 column provides greater
1 1
selectivity for the iron cyanide complex. The 2-mm column requires ⁄4 the sample volume and operates at ⁄4 the flowrate of a
4-mm column. Due to the decreased flowrate, the 2-mm column consumes only ⁄4 the eluent required by a 4-mm column.
A trademark by Dionex Corporation, Sunnyvale, CA.
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7.1.8 Guard Column—Optional low-capacity anion exchange chromatography guard column. This column may be used before
the analytical column to remove sample impurities and prevent them from passing onto the analytical column. The selected column
shall provide for adequate selectivity of highly valent metal cyanide complexes. Examples include the Dionex IonPac AG5 and
IonPac AG11 columns or equivalent (9, 10).
7.1.9 UV/Vis Detector—Liquid chromatography UV/Vis detector, capable of low wavelength detection at 215 nm.
7.1.10 Instrument Control and Data Collection System—Standard equipment such as electronic control devices and computer
and software and/or integrators for providing automatic control of the chromatography system, instrument calibration and data
analysis.
7.2 On-line Sample Preconcentration Accessories—Additional electrical contact closures are required for establishing
automatic control of the preconcentration hardware accessories.
7.2.1 Injection Valve—-way switching valve capable of injecting volumes ranging from 0.1 μL to 1 mL.
7.2.2 Autosampler—Capable of handling 40 mL sample vials for use in performing sample preconcentration.
7.2.3 Large Sample Vials—40 mL amber glass vials. The use of self-sealing vials is recommended to prohibit exposure of the
sample to light during and after sample injection so as to prevent photodecomposition of some metal cyanide complexes.
7.2.4 Concentrator Column—Low-capacity anion exchange chromatography concentrator column. The selected column shall
provide for adequate selectivity of highly valent transition metal cyanide complexes. Examples are the Dionex IonPac AG5 and
IonPac AG11 columns or equivalent.
7.2.5 Metal Free Trap Column (MFC)—Specially designed column for the on-line cleanup of eluent ionic transition metal
impurities. Two such columns should be installed; one between the gradient pump outlet and the injection valve and the other
between the sample concentrator pump outlet and the injection valve (see 7.2.1). An example is the Dionex IonPac MFC-1 or
equivalent (12). Refer to the manufacturer’s instructions for column preparation and clean-up.
7.2.6 Sample Concentrator Pump—Liquid chromatography or otherwise equivalent pump capable of interfacing with the
instrument control and data collection system. The selected sample pump must be capable of delivering a constant flow in the range
of 1 to 5 mL/min at a pressure of 200 to 2000 psi.1379 to 13790 kPa (200 to 2000 psi).
7.3 Plastic Volumetric Flasks—1000 mL and 100 mL.
7.4 Amber Reagent Bottles—1000 mL and 100 mL.
7.5 Membrane Syringe Filters—25 mm diameter, 0.2 to 0.45 μm pore size, having low background extractables, used to filter
sample particulates.
7.6 Plastic Syringes—5 and 10 mL volumes.
7.7 pH Electrode and Meter.
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals must be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water conforming to
Specification D1193, Type I. It is recommended that special precautions such as routine contaminant monitoring and/or frequent
replacement of polishing cartridges be taken to ensure that the total organic carbon content of the water is ≤ 100 μg/L. This practice
will limit the elution of organic species and subsequent appearance of “ghost” peaks in the chromatograms (see 6.4). Figs. 1 and
2 provide examples of blank chromatograms.
8.3 Degassed Reagent Water—Sparge reagent water with helium gas or sonicate under vacuum for approximately 20 min to
remove dissolved gases such as carbon dioxide.
3-
8.4 Cobalt Cyanide Solution, Stock (1.00 mL = 1000 μg [Co(CN) ] )—Dissolve exactly 1.5455 g of Potassium hexacyano-
cobaltate (III) (potassium cobalt cyanide), K [Co(CN) ], with 500 mL of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL
3 6
volumetric flask. Dilute to volume with Sodium Hydroxide Solution II (see 8.34) and store at ambient temperature in a 1 L amber
reagent bottle. The solution is relatively stable and may be stored for up to one month.
3- 3-
8.5 Cobalt Cyanide I Solution, Standard (1.00 mL = 100 μg [Co(CN) ] )—Dilute exactly 10 mL of [Co(CN) ] Stock Solution
6 6
(see 8.4) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
3- 3-
8.6 Cobalt Cyanide II Solution, Standard (1.00 mL = 10 μg [Co(CN) ] )—Dilute exactly 10 mL of [Co(CN) ] Standard
6 6
Solution I (see 8.5) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare
daily with analysis.
Reagent Chemicals, American Chemical Society Specifications, Am. Chemical Soc., Washington, DC. For suggestions on the testing of reagents not listed by the
American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the Unites States Pharmacopeia and National Formulary,
U.S. Pharmaceutical Convention, Inc. (USPC), Rockville, MD.
D6994 − 15
FIG. 1 Blank Chromatogram of Reagent Water
FIG. 2 Blank Chromatogram of Reagent Water Using On-line Sample Preconcentration
3- 3-
8.7 Cobalt Cyanide III Solution, Standard (1.00 mL = 0.1 μg [Co(CN) ] )—Dilute exactly 1 mL of [Co(CN) ] Standard
6 6
Solution II (see 8.6) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare
daily with analysis.
2-
8.8 Copper Cyanide, Stock (1.00 mL = 1000 μg Cu[(CN) ] )—Combine exactly 0.6325 g of Tricyanocuprate(I) (copper
cyanide), CuCN, with 500 mL of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL volumetric flask. Add exactly 1.3844 g
of sodium cyanide, NaCN, and stir to dissolve both the copper cyanide and sodium cyanide. Dilute to volume with Sodium
Hydroxide Solution II (see 8.34), mix it at least for an hour and store at ambient temperature in a 1 L amber reagent bottle. Prepare
daily with analysis. (Warning—NaCN is extremely toxic. Avoid inhalation and skin and eye contact (see 9.1.1).) (Warning—The
2-
copper cyanide will dissolve upon addition of sodium cyanide to form the tricyanocuprate(I) complex, [Cu(CN) ] that is the
analyte of interest.)
NOTE 2—Warning: NaCN is extremely toxic. Avoid inhalation and skin and eye contact (see 9.1.1).
2-
NOTE 3—Caution: The copper cyanide will dissolve upon addition of sodium cyanide to form the tricyanocuprate(I) complex, [Cu(CN) ] that is the
analyte of interest.
2- 2-
8.9 Copper Cyanide I Solution, Standard (1.00 mL = 100 μg [Cu(CN) ] )—Dilute exactly 10 mL of [Cu(CN) ] Stock Solution
3 3
(see 8.8) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
2- 2-
8.10 Copper Cyanide II Solution, Standard (1.00 mL = 10 μg [Cu(CN) ] )—Dilute exactly 10 mL of [Cu(CN) ] Standard
3 3
Solution I (see 8.9) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare
daily with analysis.
2- 2-
8.11 Copper Cyanide III Solution, Standard (1.00 mL = 0.1 μg [Cu(CN) ] )—Dilute exactly 1 mL of [Cu(CN) ] Standard
3 3
Solution II (see 8.10) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
D6994 − 15
8.12 Eluent 1 (20 mM NaOH, 150 mM NaCN)—Place 1.6 g of Sodium Hydroxide Solution I (see 8.33) and 7.35 g of sodium
cyanide into a plastic 1 L volumetric flask. Add approximately 300 mL of degassed reagent water and swirl to dissolve. Dilute to
volume with degassed reagent water and mix thoroughly. The sodium cyanide is used to maintain the integrity of the metal cyanide
complexes throughout the analysis.
8.13 Eluent 2 (20 mM NaOH, 300 mM NaClO ·H O)—Place 1.6 g of Sodium Hydroxide Solution I (see 8.33) and 42.1 g of
4 2
sodium perchlorate monohydrate into a plastic 1 L volumetric flask. Add approximately 300 mL of degassed reagent water and
swirl to dissolve. Dilute to volume with degassed reagent water and mix thoroughly. The sodium perchlorate is used to elute the
metal cyanide complexes from the analytical column during the gradient elution.
8.14 Eluent 3 (20 mM NaOH)—Place 1.6 g of Sodium Hydroxide Solution I (see 8.33) into a plastic 1 L volumetric flask. Dilute
to volume with degassed reagent water and mix thoroughly.
-
8.15 Gold Cyanide Solution, Stock (1.00 mL = 1000 mg [Au(CN) ] )—Dissolve exactly 1.1570 g of Potassium dicyanoaurate(I)
(potassium gold cyanide), KAu(CN) , with 500 mL of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL volumetric flask.
Dilute to volume with Sodium Hydroxide Solution II (see 8.34) and store at ambient temperature in a 1 L amber reagent bottle.
The solution is relatively stable and may be stored for up to one month.
- -
8.16 Gold Cyanide I Solution, Standard (1.00 mL = 100 μg [Au(CN) ] )—Dilute exactly 10 mL of [Au(CN) ] Stock Solution
2 2
(see 8.15) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
- -
8.17 Gold Cyanide II Solution, Standard (1.00 mL = 10 μg [Au(CN) ] )—Dilute exactly 10 mL of [Au(CN) ] Standard Solution
2 2
I (see 8.16) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
- -
8.18 Gold Cyanide III Solution, Standard (1.00 mL = 0.1 μg [Au(CN) ] )—Dilute exactly 1 mL of [Au(CN) ] Standard Solution
2 2
II (see 8.17) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
8.19 Helium Gas—Ultra high purity.
4-
8.20 Iron Cyanide Solution, Stock (1.00 mL = 1000 μg [Fe(CN) ] )—Dissolve exactly 1.9929 g of Potassium hexacyanofer-
rate(III) (ferrocyanide trihydrate), K [Fe(CN) ]·3H O, with 500 mL of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL
4 6 2
volumetric flask. Dilute to volume with Sodium Hydroxide Solution II (see 8.34) and store at ambient temperature in a 1 L amber
reagent bottle. The solution is relatively stable and may be stored for up to one month.
4- 4-
8.21 Iron Cyanide I Solution, Standard (1.00 mL = 100 μg [Fe(CN) ] )—Dilute exactly 10 mL of [Fe(CN) ] Stock Solution
6 6
(see 8.20) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
4- 4-
8.22 Iron Cyanide II Solution, Standard (1.00 mL = 10 μg [Fe(CN) ] )—Dilute exactly 10 mL of [Fe(CN) ] Standard Solution
6 6
I (see 8.21) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
4- 4-
8.23 Iron Cyanide III Solution, Standard (1.00 mL = 0.1 μg [Fe(CN) ] )—Dilute exactly 1 mL of [Fe(CN) ] Standard
6 6
Solution II (see 8.22) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
2-
8.24 Nickel Cyanide Solution, Stock (1.00 mL = 1000 μg [Ni(CN) ] )—Dissolve exactly (1.4806 + 0.1107 × n) g of Potassium
tetracyanonickelate(II) (potassium nickel cyanide) mono- or polyhydrate, K [Ni(CN) ]·nH2O (where, n = number of water
2 4
molecules of hydration), with 500 mL of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL volumetric flask. Dilute to volume
with Sodium Hydroxide Solution II (see 8.34) and store at ambient temperature in a 1 L amber reagent bottle. Prepare daily with
analysis.
2- 2-
8.25 Nickel Cyanide I Solution, Standard (1.00 mL = 100 μg [Ni(CN) ] )—Dilute exactly 10 mL of [Ni(CN) ] Stock Solution
4 4
(see 8.24) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
2- 2-
8.26 Nickel Cyanide II Solution, Standard (1.00 mL = 10 μg [Ni(CN) ] )—Dilute exactly 10 mL of [Ni(CN) ] Standard
4 4
Solution I (see 8.25) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
2- 2-
8.27 Nickel Cyanide III Solution, Standard (1.00 mL = 0.1 μg [Ni(CN) ] )—Dilute exactly 1 mL of [Ni(CN) ] Standard
4 4
Solution II (see 8.26) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
8.28 Reagent Blank—Use Sodium Hydroxide Solution II (see 8.34).
D6994 − 15
-
8.29 Silver Cyanide Solution, Stock (1.00 mL = 1000 μg [Ag(CN) ] )—Dissolve exactly 1.2445 g of potassium dicyanoargen-
tate(I) (potassium silver cyanide), K[Ag(CN) ], with 500 mL of Sodium Hydroxide Solution II (see 8.34) in a 1000 mL volumetric
flask. Dilute to volume with Sodium Hydroxide Solution II (see 8.34) and store at ambient temperature in a 1 L amber reagent
bottle. Prepare daily with analysis.
- -
8.30 Silver Cyanide I Solution, Standard (1.00 mL = 100 μg [Ag(CN) ] )—Dilute exactly 10 mL of [Ag(CN) ] Stock Solution
2 2
(see 8.29) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle. Prepare daily
with analysis.
- -
8.31 Silver Cyanide II Solution, Standard (1.00 mL = 10 μg [Ag(CN) ] )—Dilute exactly 10 mL of [Ag(CN) ] Standard
2 2
Solution I (see 8.30) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
- -
8.32 Silver Cyanide III Solution, Standard (1.00 mL = 0.1 μg [Ag(CN) ] )—Dilute exactly 1 mL of [Ag(CN) ] Standard
2 2
Solution II (see 8.31) to 100 mL with Sodium Hydroxide Solution II (see 8.34). Store the solution in an amber reagent bottle.
Prepare daily with analysis.
8.33 Sodium Hydroxide Solution I (50 % w/w)—w ⁄w)—It is recommended that the solution be purchased from a vendor so as
to have the lowest possible carbonate contamination. Attempts to prepare the solution manually may result in carbonate
contamination. (Warning—This solution is only used for the preparation of reagents and is not a reagent itself.)
NOTE 4—Caution: This solution is only used for the preparation of reagents and is not a reagent itself.
8.34 Sodium Hydroxide Solution II (10 mM, pH = 12)—Place 0.8 g of Sodium Hydroxide Solution I (see 8.33) into a plastic
1 L volumetric flask. Dilute to volume with degassed reagent water and mix thoroughly. Check to ensure that the pH is ≥ 12 using
pH paper or a calibrated pH electrode. Add additional Sodium Hydroxide Solution I, if needed, to bring the pH to 12. This solution
is used in the preparation of all standards in order to match the matrix of the standards to that of the alkaline preserved samples.
In addition, the high pH acts as a safety measure to prevent formation of gaseous HCN in the event of decomposition of the metal
cyanide complex standards.
8.35 Filter Paper—Purchase suitable filter paper. Typically the filter papers have a pore size of 0.45-μm membrane. Material
such as fine-textured, ashless paper, or glass fiber paper are acceptable. The user must first ascertain that the filter paper is of
sufficient purity to use without adversely affecting the bias and precision of the test method.
9. Hazards
9.1 Safety Precautions:
9.1.1 Because of the toxicity of cyanide, exercise great care in its handling. Acidification of cyanide solutions produces lethal,
toxic hydrogen cyanide (HCN) gas. Prepare all cyanide containing solutions within a ventilation hood. Wear hand and eye
protection at all times when working with cyanide.
9.1.2 Some of the reagents and solutions used in this method contain cyanide. Dispose of these materials properly. The effluent
from the chromatograph will contain cyanide. The effluent shall be collected and immediately adjusted to a pH of 12 or greater.
Dispose of the effluent properly.
10. Sampling and Sample Preservation
10.1 Collect the sample in accordance with Practices D3370.
10.2 Samples must be collected in polyethylene containers covered in aluminum foil or otherwise equivalent containers such
as those composed of amber plastic so as to filter UV light at 300 nm and below and prevent photodecomposition of iron and cobalt
cyanide complexes.
10.3 Samples for metal cyanide complex analysis must be preserved under alkaline conditions by adjusting the pH to 12 or
greater using sodium hydroxide.
10.4 Store samples at 4°C for no longer than 14 days. Samples shall be brought to room temperature prior to analysis.
11. Preparation of Apparatus
11.1 Anion Exchange Chromatography Analysis—Analyze samples containing greater than 0.20 mg/L metal cyanide complexes
by direct injection of 0.1 mL of sample.
11.1.1 Set up the chromatography hardware in an appropriate manner for analysis. An example of a suitable hardware
configuration using the method is displayed in Fig. 3.
11.2 Set up the method by programming the instrument control and data collection system or the gradient pump directly to
perform gradient elution anion chromatography analysis of metal cyanide complexes as specified in Table 1. Portions of the
analysis program, such as the gradient elution conditions, may be modified as appropriate provided the analytical results fall within
the precision and bias established for the test method (see Section 15).
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FIG. 3 Chromatograph Configuration for the Analysis of Metal Cyanides
TABLE 1 Method Settings for the Analysis of Metal Cyanides Using Gradient Elution
Gradient Pump Absorbance Detector
Comments
Time
Flow Rate Eluent 1 Eluent 2 Eluent 3 Wavelength Data Collection
and Function
(mL/min) (%) (%) (%) (nm) (Absorbance Units)
Init. 1.00 10 10 80 215 Initial Conditions
0.0 1.00 10 10 80 215 Offset baseline Analysis Gradient
18.0 1.00 10 45 45 215 Begin
22.0 1.00 10 45 45 215 End
A
25.0 1.00 10 10 80 215 Equilibration
35.0 1.00 10 10 80 215
A
The eluents are reset to their initial concentrations and allowed to pump for 10 min at the end of the analysis run to equilibrate the columns prior to the next sample
injection.
TABLE 2 Method Settings for the Analysis of Metal Cyanides Using Gradient Elution and On-line Sample Preconcentration
Two-way Sample
Gradient Pump Absorbance Detector
Switching Enrichment Comments
Time
Flow Rate Eluent 1 Eluent 2 Eluent 3 Wavelength Data Collection
Valve Pump and Function
(mL/min) (%) (%) (%) (nm) (Absorbance Units)
Position (2 mL/min)
Init. Load 1.00 10 10 80 215 Initial Conditions
0.0 Load 1.00 10 10 80 215
A
1.0 Load 1.00 10 10 80 215 On Equilibration
11.0 Inject 1.00 10 10 80 215 Off Sample Injection
11.1 Inject 1.00 10 10 80 215 Offset baseline Analysis Gradient
11.2 Inject 1.00 10 10 80 215 Begin
29.2 Inject 1.00 10 45 45 215
33.2 Load 1.00 10 45 45 215 End
A
The eluents are pumped through the guard and analytical columns at their initial concentrations for 10 min at the beginning of the analysis run to equilibrate the columns
between sample injections. During this time, the sample concentrator pump is turned on and 20 mL of sample is pumped to the concentrator column.
D6994 − 15
FIG. 4 Chromatograph Configuration for the Analysis of Metal Cyanides Using Sample Preconcentration
11.3 Anion Exchange Chromatography Analysis Using On-line Sample Preconcentration—Analyze samples containing less
than 0.20 mg/L metal cyanide complexes by using on-line sample preconcentration prior to anion exchange chromatography
analysis.
11.3.1 Set up the chromatography hardware for performing analysis with initial on-line sample preconcentration. An example
of a suitable hardware configuration using the method is displayed in Figs. 4 and 5.
11.3.2 Condition the MFCs per the manufacturer’s instructions and install as shown in Fig. 4.
11.3.3 Set the sample concentrator pump for a flow rate of 2 mL/min.
11.3.4 Prime the sample concentrator pump to remove trapped air. Disconnect the tubing from the pump head and withdraw
eluent using a plastic syringe until no air bubbles are observed. Reconnect the tubing when finished. (Warning—The effluent from
the chromatograph will contain cyanide and should be handled and disposed of properly. See 9.1.2.)
NOTE 5—Warning: The effluent from the chromatograph will contain cyanide and should be handled and disposed of properly. See 9.1.2.
11.4 Prime the gradient pump to remove trapped air within each eluent line separately. Select one eluent, set to 100 %, and begin
priming. Repeat this step for the remaining eluents.
11.5 Prime the gradient pump once more using the initial method settings.
11.6 Condition the anion trap column according to the manufacturer’s instructions.
11.6.1 Connect the anion trap column directly to the outlet of the gradient pump. Set the pump to 100 % Eluent 1 (see 8.12)
and pump this through the column at 1 mL/min for 60 min to convert the resin from the hydroxide to the cyanide form. At the
end of the time period, stop the gradient pump and disconnect the anion trap column from the outlet of the gradient pump. Dispose
of the contents of the waste beaker as hazardous waste.
11.6.2 Place the conditioned anion trap column between the Eluent 1 reservoir and the gradient pump inlet as shown in Figs.
3 and 4. (Warning—The anion trap column is capable of treating only a limited amount of Eluent 1. For optimum performance,
the column must be reconditioned at a minimum following treatment of each 2 to 3 L of Eluent 1.)
NOTE 6—Caution: The anion trap column is capable of treating only a limited amount of Eluent 1. For optimum performance, the column must be
reconditioned at a minimum following treatment of each 2 to 3 L of Eluent 1.
11.7 Reprime the Eluent 1 gradient pump line.
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FIG. 5 Injection Valve Configuration for Sample Preconcentration
11.8 Connect the guard and analytical columns between the injection valve and the inlet of the UV/Vis detector. Ensure that the
columns are oriented in the appropriate direction for eluent flow.
11.9 Allow the instrument to equilibrate for at least 10 min prior to the analysis by pumping eluent through the concentrator
column (if present), guard and analytical columns at a flow rate of 1 mL/min using the initial eluent settings.
11.10 Set the UV/Vis detector to 215 nm and offset the absorbance to zero. (Warning—Eluent is pumped through the
concentrator column by placing the injection valve in the “Inject” mode (see Fig. 5).)
NOTE 7—Caution: Eluent is pumped through the concentrator column by placing the injection valve in the “Inject” mode (see Fig. 5).
12. Calibration
4-
NOTE 8—Caution: Since all iron cyanide complexes are detected as ferrocyanide ([Fe(CN) ] ), this form of iron cyanide is used in the preparation
of the calibration standards.
4-
12.1 (Warning—Since all iron cyanide complexes are detected as ferrocyanide ([Fe(CN) ] ), this form of iron cyanide is used
in the preparation of the calibration standards.)
12.2 Prepare calibration standards so as to bracket the calibration ranges of each of the metal cyanide complexes by adding
measured volumes of the metal cyanide standards (see Section 8) to volumetric flasks. Approximate calibration ranges for each
metal cyanide complex are provided in Tables 3 and 4. Dilute the standards to their respective final volumes using Sodium
Hydroxide Solution II (see 8.34). Prepare at least three standards or as otherwise required for regulatory reporting. Store the
standards in amber reagent bottles.
12.3 To establish the calibration curves, analyze the reagent blank and calibration standards in accordance with the procedure
in Section 13. Plot calibration curves of peak area response versus analyte concentration for each metal cyanide using the reagent
blank peak area integration for the zero point. Perform regressions of the plots. The correlation coefficient of each regression should
be 0.995 or greater for accurate results. A second order regression plot may be used if needed. Once the calibration curve has been
established, verification must be performed on each analysis day, whenever fresh eluent is prepared and once per analysis batch
as outlined in 16.3 and 16.4. (Warning—The calibration and subsequent analysis results for iron cyanide should be presented as
x- 3-/4-
either [Fe(CN) ] or [Fe(CN) ] so as to represent the total sum of ferrocyanide and ferricyanide.)
6 6
x- 3-/4-
NOTE 9—Caution: The calibration and subsequent analysis results for iron cyanide should be presented as either [Fe(CN) ] or [Fe(CN) ] so as
6 6
to represent the total sum of ferrocyanide and ferricyanide.
13. Procedure
13.1 Filter an appropriate volume of sample using a plastic syringe fitted with a 0.45 μm syringe filter.filter (8.35).
13.2 Transfer the filtered sample to an amber sample vial. Repeat this procedure for the remaining samples.
13.3 Transfer the reagent blank, calibration standards and QA/QC samples (see Section 16) and standards to amber sample vials.
13.4 Place all of the vials in the autosampler.
13.5 Start the autosampler and instrument control and data collection system, if applicable, and begin analyzing the samples.
A water blank should be analyzed first to equilibrate the columns followed by the reagent blank, calibration standards (see Section
12) and samples, including QA/QC samples (see Section 16). Use an injection volume of 0.1 mL for samples containing from 0.200
D6994 − 15
TABLE 3 Approximate Calibration Ranges for Metal Cyanide
Complexes Determined by Anion Exchange Chromatography
Calibration Range
Cyanide Complex
(mg/L)
-
[Ag(CN) ] 0.5 to 100
-
[Au(CN) ] 0.2 to 50
3-
[Co(CN) ] 0.5 to 100
2-
[Cu(CN) ] 0.2 to 2.0
4-
[Fe(CN) ] 0.10 to 20
2-
[Ni(CN) ] 1.0 to 200
TABLE 4 Approximate Calibration Ranges for Metal Cyanide
Complexes Determined
...