ASTM D6994-04
(Test Method)Standard Test Method for Determination of Metal Cyanide Complexes in Wastewater, Surface Water, Groundwater and Drinking Water Using Anion Exchange Chromatography with UV Detection
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
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 ) ensures that all metal cyanide complexes are solubilized and recovered in the analysis ().
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 . 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 . 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 . 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 .
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 .
General Information
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Standards Content (Sample)
NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: D6994 – 04
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 1.5 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method covers the determination of the metal
responsibility of the user of this standard to establish appro-
cyanide complexes of iron, cobalt, silver, gold, copper and
priate safety and health practices and determine the applica-
nickel in waters including groundwaters, surface waters, drink-
bility of regulatory limitations prior to use. For specific hazard
ing waters and wastewaters by anion exchange chromatogra-
statements, refer to Section 9.
phy and UVdetection.The use of alkaline sample preservation
conditions (see 10.3) ensures that all metal cyanide complexes
2. Referenced Documents
are solubilized and recovered in the analysis (1-3).
2.1 ASTM Standards:
1.2 Metal cyanide complex concentrations between 0.20 to
D1129 Terminology Relating to Water
200 mg/Lmay be determined by direct injection of the sample.
D1192 Guide for Equipment for SamplingWater and Steam
This range will differ depending on the specific metal cyanide
in Closed Conduits
complex analyte, with some exhibiting greater or lesser detec-
D1193 Specification for Reagent Water
tion sensitivity than others. Approximate concentration ranges
D2777 Practice for Determination of Precision and Bias of
are provided in 12.1. Concentrations greater than the specific
Applicable Test Methods of Committee D19 on Water
analyte range may be determined after appropriate dilution.
D3370 Practices for Sampling Water from Closed Conduits
This test method is not applicable for matrices with high ionic
D3856 Guide for Good Laboratory Practices in Laborato-
strength (conductivity greater than 500 meq/L as Cl) and TDS
ries Engaged in Sampling and Analysis of Water
(greater than 30 000 mg/L), such as ocean water.
D5810 Guide for Spiking into Aqueous Samples
1.3 Metal cyanide complex concentrations less than 0.200
D5847 Practice for Writing Quality Control Specifications
mg/L may be determined by on-line sample preconcentration
for Standard Test Methods for Water Analysis
coupled with anion exchange chromatography as described in
D6696 Guide for Understanding Cyanide Species
11.3. This range will differ depending on the specific metal
cyanide complex analyte, with some exhibiting greater or
3. Terminology
lesser detection sensitivity than others. Approximate concen-
3.1 Definitions—For a definition of terms used in this
tration ranges are provided in 12.1. The preconcentration
method, refer to Terminology D1129.
method is not applicable for silver and copper cyanide com-
3.2 Definitions of Terms Specific to This Standard:
plexes in matrices with high TDS (greater than 1000 mg/L).
3.2.1 anion exchange chromatography—a type of liquid
1.4 The test method may also be applied to the determina-
chromatography in which anionic analytes are separated by
tion of additional metal cyanide complexes, such as those of
differential retention on an anion exchange resin and detected
platinumandpalladium.However,itistheresponsibilityofthe
by an appropriate detection mechanism.
user of this standard to establish the validity of the test method
3.2.2 eluent—the liquid mobile phase used in anion ex-
for the determination of cyanide complexes of metals other
change chromatography to transport the sample through the
than those in 1.1.
chromatography system.
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 For referenced ASTM standards, visit the ASTM website, www.astm.org, or
in Water. contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
Current edition approved March 1, 2004. Published April 2004. DOI: 10.1520/ Standards volume information, refer to the standard’s Document Summary page on
D6994-04. the ASTM website.
2 4
The boldface numbers in parentheses refer to the list of references at the end of Withdrawn. The last approved version of this historical standard is referenced
this standard. on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D6994 – 04
3.2.3 analytical column—the chromatography column that on the anion exchange column (4). The concentration range
contains the stationary phase for separation by ion exchange. will differ depending on the specific metal cyanide analyte,
The column is packed with anion exchange resin that separates with some complexes exhibiting greater or lesser detection
the analytes of interest based on their retention characteristics sensitivity than others based on their molar absorptivity. Refer
prior to detection. to 12.1 for actual concentration ranges for individual metal
3.2.4 guard column—a short chromatography column that cyanide complexes. The metal cyanide complexes are eluted
is placed before the analytical column to protect it from from the column by the eluent gradient and detected as signal
particulates and impurities that may cause fouling. peaks using UV absorption at 215 nm. Their concentrations in
3.2.5 anion trap column—a high-capacity, low-pressure the sample are determined by comparison of the analyte peak
anion exchange column used to remove reagent impurities area with a standard calibration plot. Under the alkaline
3-
from the eluent stream. The anion trap column is placed conditions of the analysis, ferricyanide ([Fe(CN) ] )isre-
4-
between the eluent reservoir and the gradient pump. duced to ferrocyanide ([Fe(CN) ] ) (1,2), yielding a single
3.2.6 gradient elution—a type of elution in which the eluent analyte peak. Any unreduced ferricyanide will be exhibited as
composition is steadily altered throughout the analysis in order tailing on the ferrocyanide peak.
to provide for an adequate separation of the analytes of interest 4.2 Forsamplescontainingfrom0.50to200µg/L,dissolved
prior to detection. metal cyanide complexes are determined by using anion
3.2.7 gradientpump—aliquidchromatographypumpthatis exchange chromatography coupled with on-line sample pre-
capable of performing gradient elutions. concentration (4,5).Twenty mLof sample is passed through an
3.2.8 total cyanide—the sum total of all of the inorganic anion exchange concentrator column. As the sample passes
chemical forms of cyanide. Total cyanide thus includes both through the column, the metal cyanide complexes are retained
free cyanide and anionic metal cyanide complexes. and concentrated on the column while the remainder of the
3.2.9 metal cyanide complex—a negatively charged ionic sample matrix is directed to waste. Following concentration,
complex consisting of one or more cyanide ions bound to a the metal cyanide analytes are eluted from the concentrator
single transition metal cation. Also referred to as metal- column through gradient elution, into the chromatograph and
complexed cyanides, these complexes have the general for- onto an anion exchange column where the remainder of the
mula: analysis is completed as described in 4.1.The calibration range
for metal cyanide complexes using sample preconcentration
x2
@M~CN! # (1)
b
method is between 0.50 to 200 µg/L. This range will differ
depending on the specific metal cyanide analyte, with some
where:
M = transition metal cation, complexes exhibiting greater or lesser detection sensitivity
b = number of cyanide groups, and
than others based on their molar absorptivity. Refer to 12.1 for
x = ionic charge of the transition metal complex.
actual concentration ranges for individual metal cyanide com-
3.2.9.1 Discussion—Metalcyanidecomplexesarerelatively
plexes.
stableandrequiremoderatetohighlyacidicconditionsinorder
5. Significance and Use
to dissociate and form free cyanide. Based on their stability,
metal cyanide complexes are divided into two categories: 5.1 This method directly determines the concentration of
“weak metal cyanide complexes” and “strong metal cyanide
metalcyanidecomplexesinenvironmentalwaters.Themethod
complexes.” Examples of strong metal cyanide complexes is important from an environmental regulatory perspective
include the iron cyanide complexes prevalent in many cyanide
because it differentiates metal cyanide complexes of lesser
containing industrial wastewaters.The iron cyanide complexes toxicity from metal cyanide complexes of greater toxicity.
are considered to be among the most stable and least toxic
Previous determinations of strong metal cyanide complexes
forms of cyanide. Refer to Guide D6696 for a more detailed assumed that the concentration of strong metal cyanide com-
discussion of aqueous cyanide species. plexes is equivalent to the difference between the total cyanide
3.2.9.2 Discussion—Themetalcyanidecomplexescanform and the free cyanide. This approach is subject to error because
salts with a variety of alkali and transition metal cations.These different methods used to determine free cyanide often provide
alkali metal cyanide complex salts are soluble under alkaline widelyvaryingresults,thusimpactingthestrongmetalcyanide
conditions (1-3). complex concentration that is determined by difference. The
3.2.10 free cyanide—the form of cyanide recognized as direct analysis using anion exchange chromatography avoids
being bioavailable and toxic. Free cyanide may be present as these method biases and provides for a more accurate and
either molecular HCN or the anion CN- depending on the pH precise determination of metal cyanide complexes.
conditions. Refer to Guide D6696 for a more detailed discus-
6. Interferences
sion of aqueous cyanide species.
6.1 Photodecomposition of some metal cyanide complexes
4. Summary of Test Methods
such as those of iron can reduce their concentration (6-8).
4.1 Dissolved metal cyanide complexes are determined by Samples shall be collected so as to prevent exposure to light
anion exchange chromatography. For samples containing from (see 10.2). Samples shall be analyzed in amber bottles and
0.2 to 200 mg/L metal cyanides a sample volume of 0.1 mL is protected from light whenever possible.
injected directly into the ion chromatograph where the metal 6.2 Carbonate is not a method interference but can accumu-
cyanide analytes are separated by being differentially retained late by adherence to the anion exchange resin of the analytical
D6994 – 04
column. This may eventually lead to unstable baselines and a dissolved solids.Any matrix with high ionic strength and total
reduction in column capacity and analyte retention. Care shall dissolved solids (TDS > 1000 mg/L) could affect the perfor-
be taken to avoid carbonate contamination when preparing and mance of the analytical columns when performing sample
using sodium hydroxide eluents (9,10). preconcentration, which may result in poor separation and
recovery of metal cyanide complexes.
NOTE 1—Caution: Carbonate is formed in sodium hydroxide solutions
by reaction with atmospheric carbon dioxide. Prepare all eluents using
7. Apparatus
reagent water degassed by helium sparging or vacuum sonication to
prevent carbonate contamination as well as eluent outgassing during the
7.1 Anion Exchange Chromatography Apparatus Require-
analysis. Guidelines are provided in the test method for preparing
ments:
low-carbonate sodium hydroxide eluent and reagent solutions (see Refs
7.1.1 Pressurized Eluent Reservoir—Accessories must in-
9,10).
clude a gas regulator capable of maintaininga2to10psi head
6.3 Commercial grade sodium cyanide used in the prepara-
pressure on the eluent solutions using helium gas.
tion of Eluent 1 (see 8.12) often contains metal cyanide
7.1.2 PressurizableEluentBottles—Bottlesmustbecapable
complex impurities.These impurities can cause noisy, unstable
of withstanding an internal pressure of 7 to 10 psi. The bottles
baselines during the gradient elution profile.The installation of
must be made of a chemically inert plastic such as polypropy-
an anion trap column between the Eluent 1 reservoir and the
lene, suitable for use with sodium hydroxide-based eluents.
gradient pump removes the impurities from the eluent stream
7.1.3 Tubing—To be used with the eluent reservoir and
resulting in improved chromatographic baselines. Guidelines
made of a material that is compatible with the eluent solutions.
for preparing and installing the anion trap column are provided
7.1.4 Gradient Pump—High performance liquid chroma-
in the test method (see 7.1.6 and 11.6).
tography (HPLC) or ion chromatography (IC) pump capable of
6.4 The IonPact AG5, AG11, AS5 and AS11 chromatogra-
delivering a constant flow in the range of 1 to 5 mL/min at a
phy columns referenced in the test method (see 7.1.7, 7.1.8,
pressure of 200 to 2000 psi.
and 7.2.4) are polymeric and accordingly will concentrate
7.1.5 Chromatography Tubing—The tubing must be pres-
neutral organics and polyvalent organic anions at the head of
sure resistant (approximately 3000 psi) and made of a material
the column. Organic species containing a carbonate functional
that is compatible with the eluent solutions. Examples of
group will absorb at 215 nm. These species can potentially
suitable materials are PEEK and 316 stainless steel.
cause “ghost” peaks when eluted during the analysis. This
7.1.6 Anion Trap Column—The anion trap column is a low
effect is a function of the quality of the water used in the
pressure column that is placed between the Eluent 1 reservoir
preparation of the eluent solutions as well as the column
and the gradient pump inlet to trap and remove metal cyanide
equilibration time. Sample preconcentration will enhance this
impurities. The column is packed with a high-capacity anion
effect. High purity reagent water containing as low a concen-
exchange resin.An example of a suitable column is the Dionex
tration as possible of organic contaminants should be used in
IonPac ATC-3 4-mm (9 by 24 mm) or equivalent (11). The
the preparation of reagents (see 8.2).
column must be composed of a material appropriate for use
6.5 Free metal cations present in either the sample matrix or
with sodium hydroxide eluents.
as impurities in the combined eluent stream can combine with
7.1.7 Analytical Colum
...
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