ASTM D7284-08
(Test Method)Standard Test Method for Total Cyanide in Water by Micro Distillation followed by Flow Injection Analysis with Gas Diffusion Separation and Amperometric Detection
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
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.
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. The 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 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 400 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 method utilizes flow injection with amperometric detection based on Test Method D 6888. 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 D 2036.
1.5 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 Note 2 and Section 9.
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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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.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: D7284 − 08
StandardTest 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 D2777 Practice for Determination of Precision and Bias of
Applicable Test Methods of Committee D19 on Water
1.1 This test method is used to determine the concentration
D3856 Guide for Management Systems in Laboratories
of total cyanide in an aqueous wastewater or effluent. The
- Engaged in Analysis of Water
method detects the cyanides that are free (HCN and CN ) and
D5847 Practice for Writing Quality Control Specifications
strong-metal-cyanide complexes that dissociate and release
for Standard Test Methods for Water Analysis
free cyanide when refluxed under strongly acidic conditions.
D6696 Guide for Understanding Cyanide Species
1.2 This method may not be applicable to process solutions
D6888 Test Method for Available Cyanide with Ligand
from precious metals mining operations.
Displacement and Flow InjectionAnalysis (FIA) Utilizing
Gas Diffusion Separation and Amperometric Detection
1.3 This procedure is applicable over a range of approxi-
mately 2 to 400 µg/L (parts per billion) total cyanide. Higher D7365 Practice for Sampling, Preservation and Mitigating
Interferences in Water Samples for Analysis of Cyanide
concentrations can be measured with sample dilution or lower
injection volume.
3. Terminology
1.4 The determinative step of this method utilizes flow
injection with amperometric detection based on Test Method 3.1 Definitions:
D6888. Prior to analysis, samples must be distilled with a
3.1.1 For definitions of terms used in this test method, refer
micro-distillation apparatus described in this test method or
to Terminology D1129 and Guide D6696.
with a suitable cyanide distillation apparatus specified in Test
3.1.2 total cyanide—Total cyanide is an analytically defined
Methods D2036.
term that refers to the sum total of all of the inorganic chemical
forms of cyanide that dissociate and release free cyanide when
1.5 This standard does not purport to address all of the
refluxed under strongly acidic conditions. Total cyanide is
safety concerns, if any, associated with its use. It is the
determined analytically through strong acid distillation or UV
responsibility of the user of this standard to establish appro-
radiation followed by analysis of liberated free cyanide on
priate safety and health practices and determine the applica-
aqueous samples preserved with NaOH (pH~12). In water,
bility of regulatory limitations prior to use. Specific hazard
total cyanide includes the following dissolved species: free
statements are given in Note 2 and Section 9.
cyanide, weak acid dissociable metal cyanide complexes and
strong metal cyanide complexes. Also, some of the strong
2. Referenced Documents
metal cyanide complexes, such as those of gold, cobalt and
2.1 ASTM Standards:
platinum, might not be fully recovered during the total cyanide
D1129 Terminology Relating to Water
analytical procedure. Additionally, total cyanide may also
D1193 Specification for Reagent Water
include some organic forms of cyanide such as nitriles that
D2036 Test Methods for Cyanides in Water
release free cyanide under the conditions of the analysis.
4. Summary of Test Method
This test method is under the jurisdiction of ASTM Committee D19 on Water
andisthedirectresponsibilityofSubcommitteeD19.06onMethodsforAnalysisfor
4.1 The samples are distilled with a strong acid in the
Organic Substances in Water.
presence of magnesium chloride catalyst and captured in
Current edition approved April 1, 2008. Published April 2008. DOI: 10.1520/
sodium hydroxide absorber solution.
D7284-08.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
4.2 The absorber solution is introduced into a flow injection
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
analysis (FIA) system where it is acidified to form hydrogen
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. cyanide (HCN). The hydrogen cyanide gas diffuses through a
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7284 − 08
hydrophobic gas diffusion membrane, from the acidic donor oxidantsproduceselementalsulfur,sulfur(IV)oxide,aswellas
stream into an alkaline acceptor stream. carbonyl sulfide which eventually leads to the formation of
2-
sulfite ion (SO ) in the NaOH absorbing solution. The sulfite
4.3 The captured cyanide is sent to an amperometric flow-
ion slowly oxidizes cyanide to cyanate resulting in a negative
celldetectorwithasilver-workingelectrode.Inthepresenceof
interference. Therefore, samples that are known to contain
cyanide, silver in the working electrode is oxidized at the
significant amounts of thiocyanate may need to be analyzed
applied potential. The anodic current measured is proportional
with a method that does not require distillation, for example,
to the concentration of cyanide.
available cyanide by Test Method D6888.
4.4 Calibrations and data are processed with the instru-
6.1.2.1 During the validation study, synthetic samples con-
-
ment’s data acquisition software.
tainingupto15mg/LSCN and25mg/LNO asNyieldedless
- -
than 0.5 % of the SCN to be measurable CN . For example, a
5. Significance and Use
solutionthatdidnotcontainanyknownamountofcyanide,but
-
5.1 Cyanide and hydrogen cyanide are highly toxic. Regu-
did contain 15-mg/L SCN and 25 mg/L NO as N, was
-
lations have been established to require the monitoring of
measured as 53.1 µg/L CN .
cyanide in industrial and domestic wastes and surface waters.
7. Apparatus and Instrumentation
5.2 This test method is applicable for natural waters, indus-
7.1 The instrument should be equipped with a precise
trial wastewaters and effluents.
sample introduction system, a gas diffusion manifold with
6. Interferences hydrophobic membrane, and an amperometric detection sys-
tem to include a silver working electrode, aAg/AgCl reference
6.1 Improper sample collection or pretreatment can result in
electrode, and a Pt or stainless steel counter electrode. The
significant positive or negative bias, therefore it is imperative
apparatus schematic is shown in Fig. 1, and example instru-
that samples be collected and mitigated for interferences as
ment settings are shown in Table 1.
described in Practice D7365.
6.1.1 Sulfide captured in the absorber solution above 50- NOTE 1—The instrument settings in Table 1 are only examples. The
2-
analyst may modify the settings as long as performance of the method has
mg/L S will diffuse through the gas diffusion membrane
notbeendegraded.Contacttheinstrumentmanufacturerforrecommended
during flow injection analysis and can be detected in the
instrument parameters.
amperometric flowcell as a positive response. Refer to Section
7.1.1 An autosampler is recommended but not required to
11.2 for sulfide abatement.
automate sample injections and increase throughput.Autosam-
6.1.2 Thiocyanate in the presence of oxidants (for example,
plers are usually available as an option from the instrument’s
nitrates, hydrogen peroxide, chlorine or chloramine, Caro’s
manufacturer.
acid), can decompose to form cyanide during the distillation
7.1.2 Data Acquisition System—Use the computer hardware
resulting in positive interference regardless of the determina-
and software recommended by the instrument manufacturer to
tive step (amperometry, colorimetry, etc.). During acidic dis-
control the apparatus and to collect data from the detector.
tillation, decomposition of thiocyanate in the absence of
Both the OI Analytical CN Solution and Lachat Instruments QuikChem
Automated Ion Analyzer have been found to be suitable for this analysis.
40 CFR Part 136.
FIG. 1 Flow Injection Analysis Apparatus
D7284 − 08
TABLE 1 Flow Injection Analysis Parameters
7.2.1 Micro-Distillation Apparatus consisting of a distilla-
FIA Instrument Parameter Recommended Method Setting tion sample tube, stop ring, membrane, and collection vessel
Pump Flow Rates 0.5 to 2 mL/min
containing 1.0 M sodium hydroxide and a breakaway collec-
Cycle period (total) Approximately 120 seconds
tion tube as shown in Fig. 2.
Sample load period At least enough time
to completely fill the 7.2.2 Heater block assembly, temperature controlled, ca-
sample loop prior
pable of heating the MicroDist tubes to 120°C.
to injection
8. Reagents and Materials
Injection valve rinse time At least enough time
between samples to rinse the sample loop
8.1 Purity of Reagents—Reagent grade chemicals shall be
Peak Evaluation Peak height or area used in all tests. Unless otherwise indicated, it is intended that
Working Potential 0.0 V vs Ag/AgCl
all reagents shall conform to the specifications of theAmerican
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
7.1.3 Pump Tubing—Use tubing recommended by instru-
without lessening the accuracy of the determination.
ment manufacturer. Replace pump tubing when worn, or when
8.2 Purity of Water—Unless otherwise indicated, references
precision is no longer acceptable.
to water shall be understood to mean reagent water that meets
7.1.4 Gas Diffusion Membranes—Ahydrophobicmembrane
the purity specifications of Type I or Type II water, presented
which allows gaseous hydrogen cyanide to diffuse from the
in Specification D1193.
donor to the acceptor stream at a sufficient rate to allow
detection. The gas diffusion membrane should be replaced
8.3 Sodium Hydroxide Solution (1.00 M)—Dissolve 40 g
when the baseline becomes noisy or every 1 to 2 weeks.
NaOH in laboratory water and dilute to 1 L.
7.1.5 Use parts and accessories as directed by instrument
8.4 Absorber Solution for MIDI Distillations (0.25 M
manufacturer.
NaOH)—Dissolve10gNaOHinlaboratorywateranddiluteto
7.2 Distillation Apparatus—The MicroDist System de-
1L.
scribed below was utilized during the laboratory study to
8.5 Acceptor Solution (0.10 M NaOH) —Dissolve 4.0 g
demonstrate precision and bias for this test method. A larger
NaOH in laboratory water and dilute to 1 L.
distillation apparatus such as the MIDI distillation described in
-
8.6 Stock Cyanide Solution (1000 µg/mL CN )—Dissolve
section 7 of Test Methods D2036 can also be used to prepare
2.51 g of KCN and 2.0 g of NaOH in 1 Lof water. Standardize
samples prior to flow injection analysis, but the user is
with silver nitrate solution as described in Test Methods
responsible to determine the precision and bias.
The sole source of supply of the apparatus known to the committee at this time
isLachatInstruments,PNA17001(subjecttoUSReg.PatentNo.5,022,967).Ifyou
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.
Reagent Chemicals, American Chemical Society Specifications , American
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
The sole source of supply of the apparatus known to the committee at this time
listed by the American Chemical Society, see Analar Standards for Laboratory
is PALL Life Sciences Part Number M5PU025, OI Analytical Part Number
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
A0015200, and Lachat Instruments Part Number 50398. If you are aware of
and National Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville,
alternative suppliers, please provide this information to ASTM International
MD.
Headquarters.Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend.
FIG. 2 MicroDist Sample Tube
D7284 − 08
D2036, section 16.2. Store the solution under refrigeration and 8.14 Lead Acetate Test Strips—Moisten lead acetate test
check concentration approximately every 6 months and correct strips with acetate buffer prior to use.
if necessary.
8.15 Ag/AgCl Reference Electrode Filling Solution —Fill
the reference electrode as recommended by the instrument
NOTE 2—Warning: Because KCN is highly toxic, avoid contact or
inhalation.
manufacturer.
8.7 Intermediate Cyanide Standards :
8.16 Distillation Reagents:
-
8.7.1 Intermediate Standard 1 (100 µg/mL CN )—Pipette
8.16.1 Sulfamic Acid—Dissolve 9.6 g sulfamic acid into a
10.0 mL of stock cyanide solution (see 8.6) into a 100 mL
100-mL volumetric flask partially filled with water. Dilute to
volumetric flask containing 1 mL of 1.0 M NaOH (see 8.3).
volume with water.
Dilute to volume with laboratory water. Store under refrigera-
8.16.2 Cyanide Releasing Agent—Dissolve 16.1 g magne-
tion. The standard should be stable for at least 2 weeks.
sium chloride hexahydrate, MgCl -6H O, into 55.5-mL water.
- 2 2
8.7.2 Intermediate Cyanide Solution 2 (10 µg/mL CN )—
Carefully add 38-mL concentrated sulfuric acid, H SO , into
2 4
Pipette 10.0 mLof Intermediate Cyanide Solution 1 (see 8.7.1)
the solution. The solution will become very hot. Allow the
into a 100 mL volumetric flask containing 1.0 mL of 1.00 M
solution to cool prior to use. Warning: Prepare in a fume hood
NaOH (see 8.3). Dilute to volume with laboratory water. The
since HCl fumes will be liberated.
standard should be stable for at least 2 weeks.
8.8 Working Cyanide Calibration Standards—Prepare fresh
9. Hazards
daily as described in 8.8.1 and 8.8.2 ranging in concentration
9.1 Warning: Because of the toxicity of cyanide, great care
-
from 2 to 400 µg/mL CN .
must be exercised in its handling. Acidification of cyanide
8.8.1 Calibration Standards (50, 100, 200, and 400 µg/mL
solutions produces toxic hydrocyanic acid (HCN).All manipu-
-
CN )—Pipette 50, 100, 200, 400, and 400 µL of Intermediate
lations must be done in the hood so that any HCN gas that
Standard 1 (see 8.7.1) into separate 100 mL volumetric flasks
might escape is safely vented.
containing1.0mLof1.00MNaOH(see8.3).Dilutetovolume
with laboratory water. 9.2 Warning: Many of the reagents used in these test
-
methods are highly toxic. These reagents and their solutions
8.8.2 Calibration Standards (2, 5, and 10 µg/mL
...
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