ASTM D7284-20

Standard Test Method for Total Cyanide in Water by Micro Distillation followed by Flow Injection Analysis with Gas Diffusion Separation and Amperometric Detection

SIGNIFICANCE AND USE
5.1 Cyanide and hydrogen cyanide are highly toxic. Regulations have been established to require the monitoring of cyanide in industrial and domestic wastes and surface waters.3  
5.2 This test method is applicable for natural waters, industrial wastewaters and effluents.
SCOPE
1.1 This test method is used to determine the concentration of total cyanide in an aqueous wastewater or effluent. This test method detects the cyanides that are free (HCN and CN–) and strong-metal-cyanide complexes that dissociate and release free cyanide when refluxed under strongly acidic conditions.  
1.2 This test method may not be applicable to process solutions from precious metals mining operations.  
1.3 This procedure is applicable over a range of approximately 2 to 500 μg/L (parts per billion) total cyanide. Higher concentrations can be measured with sample dilution or lower injection volume.  
1.4 The determinative step of this test method utilizes flow injection with amperometric detection based on Test Method D6888. Prior to analysis, samples must be distilled with a micro-distillation apparatus described in this test method or with a suitable cyanide distillation apparatus specified in Test Methods D2036.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 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, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in 8.6 and Section 9.  
1.7 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.

General Information

• Status: Published
• Publication Date: 31-Jul-2020
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: D19 - Water
• Drafting Committee: D19.06 - Methods for Analysis for Organic Substances in Water

Relations

• Replaces: ASTM D7284-13(2017) - Standard Test Method for Total Cyanide in Water by Micro Distillation followed by Flow Injection Analysis with Gas Diffusion Separation and Amperometric Detection
• Effective Date: 01-Aug-2020
• Refers: ASTM D6888-16(2023) - Standard Test Method for Available Cyanides with Ligand Displacement and Flow Injection Analysis (FIA) Utilizing Gas Diffusion Separation and Amperometric Detection
• Effective Date: 15-Nov-2023
• 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 E691-13 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-May-2013
• 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 E691-11 - Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
• Effective Date: 01-Nov-2011
• 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 D7365-09a - Standard Practice for Sampling, Preservation and Mitigating Interferences in Water Samples for Analysis of Cyanide
• Effective Date: 01-Oct-2009
• Refers: ASTM D2036-09 - Standard Test Methods for Cyanides in Water
• Effective Date: 01-Oct-2009
• Refers: ASTM D6888-09 - Standard Test Method for Available Cyanide with Ligand Displacement and Flow Injection Analysis (FIA) Utilizing Gas Diffusion Separation and Amperometric Detection
• Effective Date: 01-Oct-2009

Overview

ASTM D7284-20 is a widely recognized standard test method developed by ASTM International for determining the concentration of total cyanide in water. This method utilizes micro distillation followed by flow injection analysis (FIA) with gas diffusion separation and amperometric detection. Designed for high sensitivity (approximately 2 to 500 μg/L), ASTM D7284-20 supports the monitoring of cyanide, a highly toxic substance, in natural waters, industrial wastewaters, and effluents. Accurate quantification of cyanide is mandated by regulations due to its environmental and health risks, making this standard essential for laboratories and facilities that discharge or monitor water.

Key Topics

• Total Cyanide Determination: The method quantifies both free cyanide (HCN and CN–) and strong-metal-cyanide complexes that dissociate under acidic distillation, providing a comprehensive measure of all relevant forms.
• Micro Distillation: Pre-analytical distillation is performed using a specialized micro distillation apparatus to isolate and capture cyanide, ensuring sample integrity and method sensitivity.
• Flow Injection Analysis with Amperometric Detection: After distillation, samples are introduced into an FIA system where cyanide is separated via a gas diffusion membrane and detected by measuring the amperometric response at a silver electrode, offering high specificity.
• Interference and Matrix Considerations: The method incorporates guidance for recognizing and mitigating potential sample interferences (such as sulfides and thiocyanates), ensuring reliable results.
• Quality Assurance: Emphasis is placed on calibration, blank checks, spike recoveries, and control sample analysis to meet stringent QA/QC requirements.
• Applications Range: The method is applicable for water samples with cyanide concentrations from approximately 2 to 500 μg/L and can accommodate higher concentrations through dilution.

Applications

The ASTM D7284-20 standard is fundamental wherever cyanide monitoring and regulatory compliance are necessary:

• Industrial Wastewater Monitoring: Used by industries (such as metal finishing, chemical manufacturing, and mining) to ensure effluent meets environmental discharge limits for cyanide.
• Surface and Groundwater Analysis: Employed by environmental monitoring agencies and laboratories for surface water, river, and groundwater quality assessments.
• Drinking Water Supply: Supports public utilities in monitoring cyanide levels to protect human health.
• Wastewater Treatment Facilities: Facilitates operational checks and regulatory reporting by publicly owned treatment works (POTWs).
• Research and Environmental Studies: Ideal for studies that require accurate, sensitive quantification of cyanide species in various aqueous environments.

Related Standards

ASTM D7284-20 is part of a suite of water analysis standards, and its use is complemented and supported by several related ASTM documents:

• ASTM D2036: Test Methods for Cyanides in Water, providing alternative or supplementary procedures, including sample distillation.
• ASTM D6888: Test Method for Available Cyanides, covering ligand displacement and FIA with gas diffusion separation and amperometric detection.
• ASTM D7365: Practice for Sampling, Preservation and Mitigating Interferences in Water Samples for Analysis of Cyanide.
• ASTM D3856: Guide for Management Systems in Laboratories Engaged in Water Analysis.
• ASTM D1193: Specification for Reagent Water, stipulating quality requirements for analytical procedures.
• ASTM D6696: Guide for Understanding Cyanide Species, providing in-depth glossary and explanatory information.

Practical Value

Adhering to ASTM D7284-20 helps organizations consistently meet regulatory obligations for cyanide discharge and monitoring, fosters best laboratory practices, and ensures that water quality data are reliable, reproducible, and defensible. Effective implementation minimizes health and environmental risks and supports transparent, standardized communication with regulatory authorities.

Keywords: total cyanide test, cyanide in water, micro distillation, flow injection analysis, amperometric detection, environmental monitoring, ASTM standards, wastewater analysis, cyanide regulations.

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: D7284 − 20
Standard Test Method for
Total Cyanide in Water by Micro Distillation followed by
Flow Injection Analysis with Gas Diffusion Separation and
Amperometric Detection
This standard is issued under the fixed designation D7284; 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 2. Referenced Documents
1.1 This test method is used to determine the concentration 2.1 ASTM Standards:
of total cyanide in an aqueous wastewater or effluent. This test D1129 Terminology Relating to Water
–
method detects the cyanides that are free (HCN and CN ) and D1193 Specification for Reagent Water
strong-metal-cyanide complexes that dissociate and release D2036 Test Methods for Cyanides in Water
free cyanide when refluxed under strongly acidic conditions. D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
1.2 This test method may not be applicable to process
D3856 Guide for Management Systems in Laboratories
solutions from precious metals mining operations.
Engaged in Analysis of Water
1.3 This procedure is applicable over a range of approxi-
D5847 Practice for Writing Quality Control Specifications
mately 2 to 500 µg/L (parts per billion) total cyanide. Higher
for Standard Test Methods for Water Analysis
concentrations can be measured with sample dilution or lower
D6696 Guide for Understanding Cyanide Species
injection volume.
D6888 Test Method for Available Cyanides with Ligand
Displacement and Flow InjectionAnalysis (FIA) Utilizing
1.4 The determinative step of this test method utilizes flow
injection with amperometric detection based on Test Method Gas Diffusion Separation and Amperometric Detection
D7365 Practice for Sampling, Preservation and Mitigating
D6888. Prior to analysis, samples must be distilled with a
micro-distillation apparatus described in this test method or Interferences in Water Samples for Analysis of Cyanide
E691 Practice for Conducting an Interlaboratory Study to
with a suitable cyanide distillation apparatus specified in Test
Methods D2036. Determine the Precision of a Test Method
1.5 The values stated in SI units are to be regarded as
3. Terminology
standard. No other units of measurement are included in this
3.1 Definitions:
standard.
3.1.1 For definitions of terms used in this standard, refer to
1.6 This standard does not purport to address all of the
Terminology D1129 and Guide D6696.
safety concerns, if any, associated with its use. It is the
3.2 Definitions of Terms Specific to This Standard:
responsibility of the user of this standard to establish appro-
3.2.1 total cyanide, n—total cyanide is an analytically de-
priate safety, health, and environmental practices and deter-
fined term that refers to the sum total of all of the inorganic
mine the applicability of regulatory limitations prior to use.
chemical forms of cyanide that dissociate and release free
Specific hazard statements are given in 8.6 and Section 9.
cyanide when refluxed under strongly acidic conditions.
1.7 This international standard was developed in accor-
3.2.1.1 Discussion—Total cyanide is determined analyti-
dance with internationally recognized principles on standard-
cally through strong acid distillation or UV radiation followed
ization established in the Decision on Principles for the
by analysis of liberated free cyanide on aqueous samples
Development of International Standards, Guides and Recom-
preservedwithNaOH(pH~12).Inwater,totalcyanideincludes
mendations issued by the World Trade Organization Technical
the following dissolved species: free cyanide, weak acid
Barriers to Trade (TBT) Committee.
dissociable metal cyanide complexes and strong metal cyanide
complexes.Also, some of the strong metal cyanide complexes,
This test method is under the jurisdiction of ASTM Committee D19 on Water
andisthedirectresponsibilityofSubcommitteeD19.06onMethodsforAnalysisfor
Organic Substances in Water. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved Aug. 1, 2020. Published August 2020. Originally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
approved in 2008. Last previous edition approved in 2017 as D7284 – 13 (2017). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/D7284-20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7284 − 20
such as those of gold, cobalt and platinum, might not be fully 6. Interferences
recovered during the total cyanide analytical procedure.
6.1 Improper sample collection or pretreatment can result in
Additionally, total cyanide may also include some organic
significant positive or negative bias, therefore it is imperative
formsofcyanidesuchasnitrilesthatreleasefreecyanideunder
that samples be collected and mitigated for interferences as
the conditions of the analysis.
described in Practice D7365.
6.1.1 Sulfide captured in the absorber solution above 50-
4. Summary of Test Method 2–
mg/L S will diffuse through the gas diffusion membrane
4.1 The samples are distilled with a strong acid in the during flow injection analysis and can be detected in the
presence of magnesium chloride catalyst and captured in amperometric flowcell as a positive response. Refer to Section
sodium hydroxide absorber solution. 11.2 for sulfide abatement.
6.1.2 Thiocyanate in the presence of oxidants (for example,
4.2 The absorber solution is introduced into a flow injection
nitrates, hydrogen peroxide, chlorine or chloramine, Caro’s
analysis (FIA) system where it is acidified to form hydrogen
acid), can decompose to form cyanide during the distillation
cyanide (HCN). The hydrogen cyanide gas diffuses through a
resulting in positive interference regardless of the determina-
hydrophobic gas diffusion membrane, from the acidic donor
tive step (amperometry, colorimetry, etc.). During acidic
stream into an alkaline acceptor stream.
distillation, decomposition of thiocyanate in the absence of
4.3 The captured cyanide is sent to an amperometric flow-
oxidantsproduceselementalsulfur,sulfur(IV)oxide,aswellas
celldetectorwithasilver-workingelectrode.Inthepresenceof
carbonyl sulfide which eventually leads to the formation of
2–
cyanide, silver in the working electrode is oxidized at the
sulfite ion (SO ) in the NaOH absorbing solution. The sulfite
applied potential. The anodic current measured is proportional
ion slowly oxidizes cyanide to cyanate resulting in a negative
to the concentration of cyanide.
interference. Therefore, samples that are known to contain
significant amounts of thiocyanate may need to be analyzed
4.4 Calibrations and data are processed with the instru-
ment’s data acquisition software. with a test method that does not require distillation, for
example, available cyanide by Test Method D6888.
6.1.2.1 During the validation study, synthetic samples con-
5. Significance and Use
–
taining up to 15 mg/L SCN and 25 mg/L NO as N yielded
5.1 Cyanide and hydrogen cyanide are highly toxic. Regu-
– –
less than 0.5 % of the SCN to be measurable CN . For
lations have been established to require the monitoring of
example, a solution that did not contain any known amount of
cyanide in industrial and domestic wastes and surface waters.
–
cyanide, but did contain 15-mg/L SCN and 25 mg/L NO as
–
5.2 This test method is applicable for natural waters, indus-
N, was measured as 53.1 µg/L CN .
trial wastewaters and effluents.
7. Apparatus and Instrumentation
7.1 The instrument should be equipped with a precise
sample introduction system, a gas diffusion manifold with
40 CFR Part 136.
FIG. 1 Flow Injection Analysis Apparatus
D7284 − 20
hydrophobic membrane, and an amperometric detection sys- containing 1.5 mL of 1.0 M sodium hydroxide with a break-
tem to include a silver working electrode, aAg/AgCl reference away top section, guard membrane, and cap as shown in Fig.
electrode, and a Pt or stainless steel counter electrode. The 2.
apparatus schematic is shown in Fig. 1, and example instru- 7.2.2 Heater block assembly, temperature controlled, ca-
ment settings are shown in Table 1. pable of heating the micro-distillation tubes to 120°C.
NOTE 1—The instrument settings in Table 1 are only examples. The
8. Reagents and Materials
analyst may modify the settings as long as performance of the method has
notbeendegraded.Contacttheinstrumentmanufacturerforrecommended
8.1 Purity of Reagents—Reagent grade chemicals shall be
instrument parameters.
used in all tests. Unless otherwise indicated, it is intended that
7.1.1 An autosampler is recommended but not required to
all reagents shall conform to the specifications of theAmerican
automate sample injections and increase throughput.Autosam-
Chemical Society, where such specifications are available.
plers are usually available as an option from the instrument’s
Other grades may be used, provided it is first ascertained that
manufacturer.
the reagent is of sufficiently high purity to permit its use
7.1.2 Data Acquisition System—Use the computer hardware
without lessening the accuracy of the determination.
and software recommended by the instrument manufacturer to
8.2 Purity of Water—Unless otherwise indicated, references
control the apparatus and to collect data from the detector.
to water shall be understood to mean reagent water that meets
7.1.3 Pump Tubing—Use tubing recommended by instru-
the purity specifications of Type I or Type II water, presented
ment manufacturer. Replace pump tubing when worn, or when
in Specification D1193.
precision is no longer acceptable.
8.3 Sodium Hydroxide Solution (1.00 M)—Dissolve 40 g
7.1.4 Gas Diffusion Membranes—Ahydrophobicmembrane
NaOH in laboratory water and dilute to 1 L.
which allows gaseous hydrogen cyanide to diffuse from the
donor to the acceptor stream at a sufficient rate to allow
8.4 Absorber Solution for MIDI Distillations (0.25 M
detection. The gas diffusion membrane should be replaced
NaOH)—Dissolve10gNaOHinlaboratorywateranddiluteto
when the baseline becomes noisy or every 1 to 2 weeks.
1L.
7.1.5 Use parts and accessories as directed by instrument
8.5 Acceptor Solution (0.10 M NaOH)—Dissolve 4.0 g
manufacturer.
NaOH in laboratory water and dilute to 1 L.
7.2 Distillation Apparatus—The Micro-Distillation System
described below was utilized during the laboratory study to
demonstrate precision and bias for this test method. A larger
distillation apparatus such as the MIDI distillation described in
The sole source of supply of the apparatus known to the committee at this time
Section 7 of Test Methods D2036 can also be used to prepare
isLachatInstruments,PNA17001(subjecttoUSReg.PatentNo.5,022,967).Ifyou
samples prior to flow injection analysis, but the user is
are aware of alternative suppliers, please provide this information to ASTM
responsible to determine the precision and bias.
International Headquarters. Your comments will receive careful consideration at a
7.2.1 Micro-Distillation Apparatus consisting of a distilla-
meeting of the responsible technical committee, which you may attend.
ACS Reagent Chemicals, Specifications and Procedures for Reagents and
tion sample tube, hydrophobic membrane, and collector tube
Standard-Grade Reference Materials, American Chemical Society, Washington,
DC. For suggestions on the testing of reagents not listed by theAmerican Chemical
Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset,
U.K., and the United States Pharmacopeia and National Formulary, U.S. Pharma-
copeial Convention, Inc. (USPC), Rockville, MD.
Both the OI Analytical CN Solution and Lachat Instruments QuikChem
Automated Ion Analyzer have been found to be suitable for this analysis.
The sole source of supply of the apparatus known to the committee at this time
is PALL Life Sciences Part Number M5PU025, OI Analytical Part Number
A0015200, and Lachat Instruments Part Number 50398. If you are aware of
alternative suppliers, please provide this information to ASTM International
Headquarters.Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend.
TABLE 1 Flow Injection Analysis Parameters
FIA Instrument Parameter Recommended Method Setting
Pump Flow Rates 0.5 to 2 mL/min
Cycle Period (Total) Approximately 120 seconds
Sample Load Period At least enough time to completely fill
the sample loop prior to injection
Injection Valve Rinse Time Between At least enough time to rinse the sample
Samples loop
Peak Evaluation Peak height or area
Working Potential 0.0 V versus Ag/AgCl
FIG. 2 Micro Distillation Sample Tube
D7284 − 20
–
8.6 Stock Cyanide Solution (1000 µg/mL CN )—Dissolve 8.13 Acetate Buffer—Dissolve 410 g of sodium acetate
2.51 g of KCN and 2.0 g of NaOH in 1 Lof water. Standardize trihydrate (NaC H O ·3H O) in 500 mL of laboratory water.
2 3 2 2
with silver nitrate solution as described in Test Methods Add glacial acetic acid (approximately 500 mL) to yield a pH
D2036, section 16.2. Store the solution under refrigeration and of 4.5.
check concentration approximately every 6 months and correct
8.14 Lead Acetate Test Strips—Moisten lead acetate test
if necessary. (Warning—Because KCN is highly toxic, avoid
strips with acetate buffer prior to use.
contact or inhalation.)
8.15 Ag/AgCl Reference Electrode Filling Solution—Fillthe
8.7 Intermediate Cyanide Standards:
reference electrode as recommended by the instrument manu-
–
8.7.1 Intermediate Standard 1 (100 µg/mL CN )—Pipette
facturer.
10.0 mL of stock cyanide solution (see 8.6) into a 100 mL
8.16 Distillation Reagents:
volumetric flask containing 1 mL of 1.0 M NaOH (see 8.3).
8.16.1 Sulfamic Acid—Dissolve 9.6 g sulfamic acid into a
Dilute to volume with laboratory water. Store under refrigera-
100-mL volumetric flask partially filled with water. Dilute to
tion. The standard should be stable for at least 2 weeks.
–
volume with water.
8.7.2 Intermediate Cyanide Solution 2 (10 µg/mL CN )—
8.16.2 Cyanide Releasing Agent—Dissolve 16.1 g magne-
Pipette 10.0 mLof Intermediate Cyanide Solution 1 (see 8.7.1)
sium chloride hexahydrate, MgCl -6H O, into 55.5-mL water.
into a 100 mL volumetric flask containing 1.0 mL of 1.00 M 2 2
Carefully add 38-mL concentrated sulfuric acid, H SO , into
NaOH (see 8.3). Dilute to volume with laboratory water. The
2 4
the solution. The solution will become very hot. Allow the
standard should be stable for at least 2 weeks.
solution to cool prior to use. (Warning—Prepare in a fume
8.8 Working Cyanide Calibration Standards—Prepare fresh
hood since HCl fumes will be liberated.)
daily as described in 8.8.1 and 8.8.2 ranging in concentration
–
8.17 pH Indicator Test Strips—pH indicator test strips
from 2 to 500 µg/L CN .
capable of changing color at 0.5 pH units in the range of pH 2
8.8.1 Calibration Standards (50, 100, 200, and 500 µg/L
–
to 12. More than one test strip may be necessary to cover this
CN )—Pipette 50, 100, 200, and 500 µL of Intermediate
range.
Standard 1 (see 8.7.1) into separate 100 mL volumetric flasks
containing1.0mLof1.00MNaOH(see8.3).Dilutetovolume
9. Hazards
with laboratory water.
–
8.8.2 Calibration Standards (2, 5, and 10 µg/L CN )—
9.1 Warning—Because of the toxicity of cyanide, great
Pipette 20, 50, and 100 µL of Intermediate Cyanide Solution 2
care must be exercised in its handling.Acidification of cyanide
(see 8.7.2) into separate 100 mL volumetric flasks containing
solutions produces toxic hydrocyanic acid (HCN).All manipu-
1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volume with
lations must be done in the hood so that any HCN gas that
laboratory water.
might escape is safely vented.
8.9 Potassium Ferricyanide Stock Solution (1000 µg/mL as
9.2 Warning—Many of the reagents used in these test
–
CN )—Weigh 0.2109 g K Fe(CN) into a 100-mL volumetric
methods are highly toxic. These reagents and their solutions
3 6
flask containing 1 mL 1 M NaOH, then dilute to volume with must be disposed of properly.
laboratory water.
9.3 All reagents and standards should be prepared in
...

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: D7284 − 13 (Reapproved 2017) D7284 − 20
Standard Test Method for
Total Cyanide in Water by Micro Distillation followed by
Flow Injection Analysis with Gas Diffusion Separation and
Amperometric Detection
This standard is issued under the fixed designation D7284; 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 is used to determine the concentration of total cyanide in an aqueous wastewater or effluent. This test
–
method detects the cyanides that are free (HCN and CN ) and strong-metal-cyanide complexes that dissociate and release free
cyanide when refluxed under strongly acidic conditions.
1.2 This test method may not be applicable to process solutions from precious metals mining operations.
1.3 This procedure is applicable over a range of approximately 2 to 500 μg/L (parts per billion) total cyanide. Higher
concentrations can be measured with sample dilution or lower injection volume.
1.4 The determinative step of this test method utilizes flow injection with amperometric detection based on Test Method D6888.
Prior to analysis, samples must be distilled with a micro-distillation apparatus described in this test method or with a suitable
cyanide distillation apparatus specified in Test Methods D2036.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 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. Specific hazard statements are given in 8.6 and Section 9.
1.6 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, health, and environmental practices and determine the applicability of
regulatory limitations prior to use. Specific hazard statements are given in 8.6 and Section 9.
1.7 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.
2. Referenced Documents
2.1 ASTM Standards:
D1129 Terminology Relating to Water
D1193 Specification for Reagent Water
D2036 Test Methods for Cyanides in Water
D2777 Practice for Determination of Precision and Bias of Applicable Test Methods of Committee D19 on Water
D3856 Guide for Management Systems in Laboratories Engaged in Analysis of Water
D5847 Practice for Writing Quality Control Specifications for Standard Test Methods for Water Analysis
D6696 Guide for Understanding Cyanide Species
D6888 Test Method for Available Cyanides with Ligand Displacement and Flow Injection Analysis (FIA) Utilizing Gas
Diffusion Separation and Amperometric Detection
D7365 Practice for Sampling, Preservation and Mitigating Interferences in Water Samples for Analysis of Cyanide
This test method is under the jurisdiction of ASTM Committee D19 on Water and is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
Organic Substances in Water.
Current edition approved July 15, 2017Aug. 1, 2020. Published July 2017August 2020. Originally approved in 2008. Last previous edition approved in 20132017 as D7284
– 13. 13 (2017). DOI: 10.1520/D7284-13R17.10.1520/D7284-20.
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’sstandard’s Document Summary page on the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7284 − 20
E691 Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method
3. Terminology
3.1 Definitions:
3.1.1 For definitions of terms used in this standard, refer to Terminology D1129 and Guide D6696.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 total cyanide, n—total cyanide is an analytically defined term that refers to the sum total of all of the inorganic chemical
forms of cyanide that dissociate and release free cyanide when refluxed under strongly acidic conditions.
3.2.1.1 Discussion—
Total cyanide is determined analytically through strong acid distillation or UV radiation followed by analysis of liberated free
cyanide on aqueous samples preserved with NaOH (pH~12). In water, total cyanide includes the following dissolved species: free
cyanide, weak acid dissociable metal cyanide complexes and strong metal cyanide complexes. Also, some of the strong metal
cyanide complexes, such as those of gold, cobalt and platinum, might not be fully recovered during the total cyanide analytical
procedure. Additionally, total cyanide may also include some organic forms of cyanide such as nitriles that release free cyanide
under the conditions of the analysis.
4. Summary of Test Method
4.1 The samples are distilled with a strong acid in the presence of magnesium chloride catalyst and captured in sodium
hydroxide absorber solution.
4.2 The absorber solution is introduced into a flow injection analysis (FIA) system where it is acidified to form hydrogen
cyanide (HCN). The hydrogen cyanide gas diffuses through a hydrophobic gas diffusion membrane, from the acidic donor stream
into an alkaline acceptor stream.
4.3 The captured cyanide is sent to an amperometric flowcell detector with a silver-working electrode. In the presence of
cyanide, silver in the working electrode is oxidized at the applied potential. The anodic current measured is proportional to the
concentration of cyanide.
4.4 Calibrations and data are processed with the instrument’sinstrument’s data acquisition software.
5. Significance and Use
5.1 Cyanide and hydrogen cyanide are highly toxic. Regulations have been established to require the monitoring of cyanide in
industrial and domestic wastes and surface waters.
5.2 This test method is applicable for natural waters, industrial wastewaters and effluents.
6. Interferences
6.1 Improper sample collection or pretreatment can result in significant positive or negative bias, therefore it is imperative that
samples be collected and mitigated for interferences as described in Practice D7365.
2–
6.1.1 Sulfide captured in the absorber solution above 50-mg/L S will diffuse through the gas diffusion membrane during flow
injection analysis and can be detected in the amperometric flowcell as a positive response. Refer to Section 11.2 for sulfide
abatement.
6.1.2 Thiocyanate in the presence of oxidants (for example, nitrates, hydrogen peroxide, chlorine or chloramine, Caro’s acid),
can decompose to form cyanide during the distillation resulting in positive interference regardless of the determinative step
(amperometry, colorimetry, etc.). During acidic distillation, decomposition of thiocyanate in the absence of oxidants produces
2–
elemental sulfur, sulfur(IV) oxide, as well as carbonyl sulfide which eventually leads to the formation of sulfite ion (SO ) in the
NaOH absorbing solution. The sulfite ion slowly oxidizes cyanide to cyanate resulting in a negative interference. Therefore,
samples that are known to contain significant amounts of thiocyanate may need to be analyzed with a test method that does not
require distillation, for example, available cyanide by Test Method D6888.
–
6.1.2.1 During the validation study, synthetic samples containing up to 15 mg/L SCN and 25 mg/L NO as N yielded less than
– –
0.5 % of the SCN to be measurable CN . For example, a solution that did not contain any known amount of cyanide, but did
– –
contain 15-mg/L SCN and 25 mg/L NO as N, was measured as 53.1 μg/L CN .
40 CFR Part 136.
D7284 − 20
7. Apparatus and Instrumentation
7.1 The instrument should be equipped with a precise sample introduction system, a gas diffusion manifold with hydrophobic
membrane, and an amperometric detection system to include a silver working electrode, a Ag/AgCl reference electrode, and a Pt
or stainless steel counter electrode. The apparatus schematic is shown in Fig. 1, and example instrument settings are shown in Table
1.
NOTE 1—The instrument settings in Table 1 are only examples. The analyst may modify the settings as long as performance of the method has not
been degraded. Contact the instrument manufacturer for recommended instrument parameters.
7.1.1 An autosampler is recommended but not required to automate sample injections and increase throughput. Autosamplers
are usually available as an option from the instrument’sinstrument’s manufacturer.
7.1.2 Data Acquisition System—Use the computer hardware and software recommended by the instrument manufacturer to
control the apparatus and to collect data from the detector.
7.1.3 Pump Tubing—Use tubing recommended by instrument manufacturer. Replace pump tubing when worn, or when
precision is no longer acceptable.
7.1.4 Gas Diffusion Membranes—A hydrophobic membrane which allows gaseous hydrogen cyanide to diffuse from the donor
to the acceptor stream at a sufficient rate to allow detection. The gas diffusion membrane should be replaced when the baseline
becomes noisy or every 1 to 2 weeks.
7.1.5 Use parts and accessories as directed by instrument manufacturer.
7.2 Distillation Apparatus—The Micro-Distillation System described below was utilized during the laboratory study to
demonstrate precision and bias for this test method. A larger distillation apparatus such as the MIDI distillation described in Section
7 of Test Methods D2036 can also be used to prepare samples prior to flow injection analysis, but the user is responsible to
determine the precision and bias.
7.2.1 Micro-Distillation Apparatus consisting of a distillation sample tube, hydrophobic membrane, and collector tube
containing 1.5 mL of 1.0 M sodium hydroxide with a breakaway top section, guard membrane, and cap as shown in Fig. 2.
7.2.2 Heater block assembly, temperature controlled, capable of heating the micro-distillation tubes to 120°C.
FIG. 1 Flow Injection Analysis Apparatus
Both the OI Analytical CN Solution and Lachat Instruments QuikChem Automated Ion Analyzer have been found to be suitable for this analysis.
The sole source of supply of the apparatus known to the committee at this time is PALL Life Sciences Part Number M5PU025, OI Analytical Part Number A0015200,
and Lachat Instruments Part Number 50398. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments
will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
The sole source of supply of the apparatus known to the committee at this time is Lachat Instruments, PN A17001 (subject to US Reg. Patent No. 5,022,967). If you
are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of
the responsible technical committee, which you may attend.
D7284 − 20
TABLE 1 Flow Injection Analysis Parameters
FIA Instrument Parameter Recommended Method Setting
Pump Flow Rates 0.5 to 2 mL/min
Cycle Period (Total) Approximately 120 seconds
Sample Load Period At least enough time to completely fill
the sample loop prior to injection
Injection Valve Rinse Time Between At least enough time to rinse the sample
Samples loop
Peak Evaluation Peak height or area
Working Potential 0.0 V versus Ag/AgCl
FIG. 2 Micro Distillation Sample Tube
8. Reagents and Materials
8.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents shall conform to the specifications of the American Chemical Society, where such specifications are available. Other
grades may be used, provided it is first ascertained that the reagent is of sufficiently high purity to permit its use without lessening
the accuracy of the determination.
8.2 Purity of Water—Unless otherwise indicated, references to water shall be understood to mean reagent water that meets the
purity specifications of Type I or Type II water, presented in Specification D1193.
8.3 Sodium Hydroxide Solution (1.00 M)—Dissolve 40 g NaOH in laboratory water and dilute to 1 L.
8.4 Absorber Solution for MIDI Distillations (0.25 M NaOH)—Dissolve 10 g NaOH in laboratory water and dilute to 1 L.
8.5 Acceptor Solution (0.10 M NaOH)—Dissolve 4.0 g NaOH in laboratory water and dilute to 1 L.
–
8.6 Stock Cyanide Solution (1000 μg/mL CN )—Dissolve 2.51 g of KCN and 2.0 g of NaOH in 1 L of water. Standardize with
silver nitrate solution as described in Test Methods D2036, section 16.2. Store the solution under refrigeration and check
concentration approximately every 6 months and correct if necessary. (Warning—Because KCN is highly toxic, avoid contact or
inhalation.)
8.7 Intermediate Cyanide Standards:
–
8.7.1 Intermediate Standard 1 (100 μg/mL CN )—Pipette 10.0 mL of stock cyanide solution (see 8.6) into a 100 mL volumetric
flask containing 1 mL of 1.0 M NaOH (see 8.3). Dilute to volume with laboratory water. Store under refrigeration. The standard
should be stable for at least 2 weeks.
–
8.7.2 Intermediate Cyanide Solution 2 (10 μg/mL CN )—Pipette 10.0 mL of Intermediate Cyanide Solution 1 (see 8.7.1) into
a 100 mL volumetric flask containing 1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volume with laboratory water. The standard
should be stable for at least 2 weeks.
8.8 Working Cyanide Calibration Standards—Prepare fresh daily as described in 8.8.1 and 8.8.2 ranging in concentration from
–
2 to 500 μg/L CN .
ACS Reagent Chemicals, American Chemical Society Specifications Specifications and Procedures for Reagents and Standard-Grade Reference Materials, , American
Chemical Society, 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 United States Pharmacopeia and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
Commercially prepared solutions of stock cyanide may be used.
D7284 − 20
–
8.8.1 Calibration Standards (50, 100, 200, and 500 μg/L CN )—Pipette 50, 100, 200, and 500 μL of Intermediate Standard 1
(see 8.7.1) into separate 100 mL volumetric flasks containing 1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volume with laboratory
water.
–
8.8.2 Calibration Standards (2, 5, and 10 μg/L CN )—Pipette 20, 50, and 100 μL of Intermediate Cyanide Solution 2 (see 8.7.2)
into separate 100 mL volumetric flasks containing 1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volume with laboratory water.
–
8.9 Potassium Ferricyanide Stock Solution (1000 μg/mL as CN )—Weigh 0.2109 g K Fe(CN) into a 100-mL volumetric flask
3 6
containing 1 mL 1 M NaOH, then dilute to volume with laboratory water.
–
8.9.1 Potassium Ferricyanide Spiking Solution (100 μg/mL CN )—Pipette 10.0 mL of potassium ferricyanide stock solution into
a 100 mL volumetric flask containing 1.0 mL of 1.00 M NaOH, then dilute to volume with laboratory water.
–
8.10 Cyanide Electrode Stabilization Solution (Approximately 2 ppm as CN )—Pipette 200 μL of Stock Cyanide (see 8.6) into
a 100 mL volumetric flask containing 1.0 mL of 1.00 M NaOH (see 8.3). Dilute to volume with laboratory water. The solution
should be stored under refrigeration.
8.11 Carrier—Water as indicated in 8.2.
8.12 Acidification and Sulfide Abatement Solution—Weigh 1.00 g bismuth nitrate pentahydrate, Bi(NO ) · 5H O, into a 1 L
3 3 2
volumetric flask. Add 55 mL of water then carefully add 55 mL of concentrated sulfuric acid to the flask. Gently swirl the flask
until the bismuth nitrate pentahydrate has dissolved in the acid solution. Carefully add water to the volumetric flask and fill to
volume.
8.13 Acetate Buffer—Dissolve 410 g of sodium acetate trihydrate (NaC H O · 3H O) in 500 mL of laboratory water. Add
2 3 2 2
glacial acetic acid (approximately 500 mL) to yield a pH of 4.5.
8.14 Lead Acetate Test Strips—Moisten lead acetate test strips with acetate buffer prior to use.
8.15 Ag/AgCl Reference Electrode Filling Solution—Fill the reference electrode as recommended by t
...