ASTM D4282-95(2001)

Designation: D 4282 – 95 (Reapproved 2001)
Standard Test Method for
Determination of Free Cyanide in Water and Wastewater by
Microdiffusion
This standard is issued under the fixed designation D 4282; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 4210 Practice for Interlaboratory Quality Control Proce-
dures and Discussion on Reporting Low-Level Data
1.1 This test method covers the determination of free
E 275 Practice for Describing and Measuring Performance
cyanides in waters and wastewaters. Free cyanide is here
of Ultraviolet, Visible, and Near Infrared Spectrophotom-
defined as the cyanide which diffuses as cyanide (HCN), at
eters
room temperature, from a solution at pH 6.
1.2 This test method does not include complexes that resist
3. Terminology
dissociation, such as hexacyanoferrates and gold cyanide, nor
3.1 Definitions:
does it include thiocyanate and cyanohydrin.
3.1.1 For a definition of terms used in this test method refer
1.3 This test method may be applied to water and wastewa-
to Terminology D 1129.
ter samples containing free cyanide from 10 to 150 μg/L.
3.2 Definitions of Terms Specific to This Standard:
Greater concentrations may be determined by appropriate
3.2.1 free cyanide—refers to those simple cyanides or
dilution.
loosely held complexes of cyanide that diffuse at pH 6, at room
1.4 This test method has been fully validated by collabora-
temperature.
tive testing as specified by Practice D 2777.
1.5 This standard does not purport to address all of the
4. Summary of Test Method
safety concerns, if any, associated with its use. It is the
4.1 The reactions are carried out in a microdiffusion cell.
responsibility of the user of this standard to establish appro-
4.2 The sample is treated with cadmium ion to precipitate
priate safety and health practices and determine the applica-
the hexacyanoferrates.
bility of regulatory limitations prior to use. For specific hazard
4.3 The sample is buffered at pH 6 and allowed to stand for
statements, see 8.6, 8.9, Section 9, and 12.2.1.
4h.
2. Referenced Documents 4.4 The HCN diffuses into sodium hydroxide solution.
4.5 An aliquot of the sodium hydroxide solution is treated
2.1 ASTM Standards:
with chloramine-T, and the cyanogen chloride formed is
D 1129 Terminology Relating to Water
reacted with barbituric acid in pyridine. The absorbance of the
D 1192 Specification for Equipment for Sampling Water
color formed is measured using a spectrophotometer at a
and Steam
3 wavelength of 580 nm.
D 1193 Specification for Reagent Water
D 2777 Practice for Determination of Precision and Bias of
5. Significance and Use
Applicable Methods of Committee D-19 on Water
5.1 This test method is useful in distinguishing between the
D 3370 Practices for Sampling Water from Closed Con-
potentially available free cyanide (total cyanide) and the free
duits
cyanide actually present.
D 3856 Guide for Good Laboratory Practices in Laborato-
5.2 This test method provides a convenient technique for
ries Engaged in Sampling and Analysis of Water
making on-site free cyanide determinations.
1 6. Interferences
This test method is under the jurisdiction of ASTM Committee D-19 on Water
and is the direct responsibility of Subcommittee D19.06 on Methods for Analysis for
6.1 Decomposition of Hexacyanoferrates During Diffusion:
Organic Substances in Water.
6.1.1 This decomposition is virtually eliminated by allow-
Current edition approved Sept. 10, 1995. Published November 1995. Originally
e 1
ing the sample to diffuse in the dark, and by precipitating the
published as D 4282 – 83. Last previous edition D 4282 – 89 (1994) .
The paper by J. M. Kruse and L. E. Thibault “Determination of Free Cyanide
hexacyanoferrates with cadmium ion.
in Ferro- and Ferricyanides,” Analytical Chemistry, 45(13): 2260–2261; 1973 Nov.,
6.2 Instability of Free Cyanide in Effluents—The reactivity
recommends a diffusion at pH 7. The ANSI modification (ANSI PH 4.41-1978) uses
pH 6. Using the conditions of the ANSI method, diffusion is completed within 4
hours at pH 6. Longer diffusion time was required at pH 7 on the samples analyzed.
3 4
Annual Book of ASTM Standards, Vol 11.01. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 4282
of free cyanide with such chemicals as aldehydes or oxidizing containing 50 mL of sodium hydroxide solution (2.05 g/L))
agents, is not really a method interference. However, because with the silver nitrate standard solution.
of this instability, it is important for the diffusion to begin as 8.6.1.2 Record the mL of titration for use in the calculation
soon after sampling as possible. It is beyond the scope of this (see Fig. 1 for an example of a typical titration curve).
test method to list all the possible cyanide reactions that may be 8.6.1.3 Calculate the concentration of the cyanide stock
encountered. solution using the following equation:
503~mL silver nitrate!5 mg/L CN in stock solution
7. Apparatus
1.00 mL of silver nitrate solution is equal to 1 mg of CN .
7.1 Diffusion Cell, microdiffusion cell, Conway type,
8.7 Potassium Phosphate Buffer Solution (Acidified)—Add
68-mm outside diameter.
8.0 mL of concentrated phosphoric acid (sp gr 1.69), H PO ,to
3 4
7.2 Micropipets, 0.10 mL, 1.00 mL.
100 mL of potassium phosphate solution.
7.3 Spectrophotometer, conforming to Practice E 275.
8.8 Potassium Phosphate Solution, 190 g/L—Add 400 mL
7.4 Spectrophotometer Cell, 1-cm equipped with a stopper.
of water to a 2-L beaker. Add and dissolve 14.5 g of sodium
7.5 Pipet or Syringe, adjustable (to deliver 1.30 mL).
hydroxide, NaOH. Add and dissolve 190 g of potassium
7.6 Calomel Reference Electrode, with saturated KNO
phosphate, monobasic, KH PO . Add water to 950 mL to aid
2 4
electrolyte, or the equivalent.
dissolution. Adjust the pH of the solution to pH 5.9 to 6.1,
7.7 pH Meter.
using 100 g/L sodium hydroxide solution. Transfer the solution
7.8 Silver Electrode.
to a 1-L volumetric flask, and dilute to volume with water.
8.9 Pyridine-Barbituric Acid Reagent—Add 15.0 g of bar-
8. Reagents
bituric acid to a 250-mL volumetric flask. Wash down the sides
8.1 Purity of Reagents—Reagent grade chemicals shall be
of the flask with just enough water to moisten the barbituric
used in all tests. Unless otherwise indicated, it is intended that
acid. Add 75 mL of pyridine and swirl to mix. Slowly add 15
reagents shall conform to the specifications of the Committee
mL of concentrated hydrochloric acid (sp gr 1.19) and swirl to
on Analytical Reagents of the American Chemical Society
mix. Cool the solution to room temperature. Dilute to volume
where such specifications are available. Other grades may be
and mix. It is recommended that this reagent be prepared fresh
used provided it is first ascertained that the reagent is of
weekly and stored in a dark place. Warning—Pyridine is
sufficient purity to permit its use without lessening the accu-
toxic; avoid contact or inhalation. Prepare this reagent in an
racy of the determination.
exhaust hood.
8.2 Purity of Water—Unless otherwise indicated, reference
8.10 Silver Nitrate Solution, Standard (1 mL = 1 mg of
to water shall be understood to mean reagent water conforming
−
CN )—Weigh 3.2647 g of silver nitrate on an analytical
to Type II of Specification D 1193.
balance. Quantitatively transfer the silver nitrate to a 1-L
8.3 Cadmium Chloride Solution (10 g/L), CdCl —Dissolve
volumetric flask. Dissolve and dilute to volume with water.
10.0 g of anhydrous cadmium chloride in 750 mL of water in
Store in a dark glass bottle.
a 1-L volumetric flask. Dilute to volume with water.
8.11 Sodium Hydroxide Solution (4.1 g/L), NaOH—Add
8.4 Chloramine-T Reagent (10 g/L)—Dissolve 1.00 g of
4.10 g of sodium hydroxide to 800 mL of water in a 1-L
chloramine-T in 50 mL of water in a 100-mL volumetric flask.
volumetric flask. Stir until dissolved, and cool the solution to
Dilute to volume with water. Make this reagent fresh daily.
− room temperature before adjusting the final volume to 1 L.
8.5 Cyanide Solution, Standard (1.00 mL = 2 μg CN )—
8.12 Sodium Hydroxide Solution (2.05 g/L), NaOH—Add
Pipet 2.00 mL of cyanide stock solution (approximately 1.0 g/L
− 2.05 g of sodium hydroxide to 800 mL of water in a 1-L
CN ) into a 1-L volumetric flask and dilute to volume with
volumetric flask. Stir until dissolved, and cool the solution to
sodium hydroxide solution (2.05 g/L).
8.6 Cyanide Solution Stock—Dissolve 2.51 g of potassium
cyanide, KCN, in 500 mL of sodium hydroxide solution (2.05
g/L) in a 1-L volumetric flask. Dilute to volume with sodium
hydroxide solution (2.05 g/L). This solution contains approxi-
−
mately 1.0 g/L cyanide (CN ). Warning—KCN is highly
toxic, avoid contact or inhalation. Prepare and standardize this
solution weekly.
8.6.1 Standardizing Cyanide Stock Solution:
8.6.1.1 Using a silver electrode and a reference electrode,
titrate 20.0 mL of the cyanide stock solution (in a beaker also
One source of supply for these cells is Arthur H. Thomas, No. 3806-F-10.
Reagent Chemicals, American Chemical Society Specifications, 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
NOTE 1—Twenty millilitres of 2.51 g/L KCN titrated with AgNO .
and National Formulary, U.S. Pharmaceutical Convention, Inc. (USPC), Rockville,
MD. FIG. 1 Typical Titration Curve Standardizing KCN Solution
D 4282
room temperature before adjusting the final volume to 1 L. (An tion standards in accordance with the procedure in Section 12.
−
alternative preparation is to dilute 0.10 N sodium hydroxide Plot a calibration curve of concentrations of CN versus
solution with an equal volume of water.) absorbance (see Fig. 2). Standards should be run daily for
calibration, until it is established that the calibration curve will
9. Hazards
apply for a longer period of time. Then it is only necessary to
−
9.1 Safety Precautions:
run two standards (such as 0 and 100 μg/L CN ) with
...