ISO 22066:2020

INTERNATIONAL ISO
STANDARD 22066
First edition
2020-09
Water quality — Determination
of total cyanide — Method using
segmented flow injection, in-line
ultraviolet digestion analysis by gas
diffusion and amperometric detection
Qualité de l'eau — Dosage du cyanure total — Méthode utilisant
l'injection en flux segmenté, l'analyse par digestion UV continue par
diffusion de gaz et la détection ampérométrique
Reference number
ISO 22066:2020(E)
©
ISO 2020

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ISO 22066:2020(E)

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© ISO 2020
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Published in Switzerland
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ISO 22066:2020(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 2
4 Principle . 2
5 Interferences . 2
5.1 Interferences by oxidizing agents . 2
5.2 Interferences by sulfide . 2
6 Reagents . 3
7 Apparatus . 6
8 Sampling and sample preparation . 7
8.1 Oxidizing agent . 7
8.2 Sulfide removal . 7
8.3 Preservation . 8
9 Procedure. 8
9.1 Flow system set up . 8
9.2 Reagent blank measurement . 8
9.3 Checking the suitability of the segmented flow analysis system . 9
9.3.1 Cyanide electrode stabilization . 9
9.3.2 Performance verification of the system . 9
9.4 Calibration . 9
9.5 Sample measurement .10
9.5.1 Cyanide measurement.10
10 Calculations.10
11 Expression of results .10
12 Test report .10
Annex A (informative) Example of a segmented flow analysis system .12
Annex B (normative) Determination of the real cyanide concentration in the potassium
cyanide solution (6.5.1) or potassium tetracyanozincate solution (6.6.1) .13
Annex C (informative) Performance data .14
Bibliography .15
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ISO 22066:2020(E)

Foreword
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The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www .iso .org/ directives).
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This document was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2,
Physical, chemical and biochemical methods.
Any feedback or questions on this document should be directed to the user’s national standards body. A
complete listing of these bodies can be found at www .iso .org/ members .html.
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ISO 22066:2020(E)

Introduction
Methods using flow analysis automated wet chemical procedures are particularly suitable for the
determination of many analytes in water in large sample series at a high analysis frequency.
Analyses can be performed by segmented flow injection analysis (SFIA) using the feature of an automatic
dosage of the sample into a flow system (manifold) where the analyte in the sample is digested with
ultraviolet radiation at 312 nm and the reagent solutions on its way through the manifold. The reaction
product is measured by a flow detector (for example amperometer).
Speciation of cyanide species can be inferred by comparing free cyanide in accordance with
ISO 17690:2015, available weak and dissociable cyanide in accordance with ISO 20950-1, and total
cyanide using this method.
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INTERNATIONAL STANDARD ISO 22066:2020(E)
Water quality — Determination of total cyanide —
Method using segmented flow injection, in-line ultraviolet
digestion analysis by gas diffusion and amperometric
detection
IMPORTANT NOTE — − The performance of this method has been established for a range of
sample matrices, which are reported in ANNEX C. These matrices represent environmental,
mining influenced and metallurgical process samples. This method is therefore recommended
for mining impacted samples. Caution is recommended for the application of alternative ISO
methods to mining influenced and metallurgical process samples if those matrices are not
explicitly mentioned in the scope; as potential biases and interferences typical for them have
not been sufficiently investigated and may not be properly mitigated.
WARNING — Persons using this document should be familiar with normal laboratory practice.
This document does not purport to address all of the safety problems, if any, associated with its
use. It is the responsibility of the user to establish appropriate safety and health practices and to
ensure neutralization and proper disposal of waste solutions.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this document
be carried out by suitably qualified staff.
1 Scope
This document specifies operationally defined methods for the determination of total cyanide in
various types of water such as drinking water, ground water, surface water, wastewaters, metallurgical
processing tailings reclaim solution, heap leach barren solution, mill slurry tailings filtrate and leaching
solutions, with cyanide concentrations from 5 µg/l to 2 000 mg/l expressed as cyanide ions in the
undiluted sample. The range of application can be extended by reducing the sensitivity (Figure A.1.).
NOTE ISO 2080:2008, 3.105, defines free cyanide. The concentration of total cyanide as defined in
ISO 2080:2008, 3.191 includes free cyanide, cyanide complexed with metals in solution as cyanide anion, but not
necessarily all of the metal cyanide complexes present as determined by a specified analytical method.
In this method, six suitable mass concentration ranges from 5 µg/l to 50 µg/l, from 50 µg/l to 500 µg/l,
from 0,5 mg/l to 5 mg/l, from 5 mg/l to 50 mg/l, from 50 mg/l to 500 mg/l and from 500 mg/l to
2 000 mg/l are described.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their content
constitutes requirements of this document. For dated references, only the edition cited applies. For
undated references, the latest edition of the referenced document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specification and test methods
ISO 5667-3, Water quality — Sampling — Part 3: Preservation and handling of water samples
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of
performance characteristics — Part 1: Statistical evaluation of the linear calibration function
ISO 8466-2, Water quality — Calibration and evaluation of analytical methods and estimation of
performance characteristics — Part 2: Calibration strategy for non-linear second-order calibration
functions
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ISO 22066:2020(E)

3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminological databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
total cyanide
sum of HCN, cyanide ions and cyanide bound in the metal-cyano complexes that are dissociated, using
digestion in the presence of ultraviolet (UV) radiation at 312 nm and sulfuric acid into HCN/CN⎺ in
accordance with this document
4 Principle
In the analytical procedure employed for determination of total cyanide the sample is treated with
ultraviolet (UV) radation at 312 nm and sulfuric acid resulting in the release of bound cyanide ion
from some metal-cyano complexes. Cyanide is not totally released from the more stable gold and cobalt
cyanide complexes.
The sample is introduced into a carrier solution of the segmented flow analysis (SFA) system via a
valve and confluence downstream with a sulfuric acid solution containing sulfide removal reagent
and digested in the presence of UV radiation at 312 nm to measure total cyanide. The released
hydrogen cyanide (HCN) gas diffuses through a hydrophobic gas diffusion membrane into an alkaline
acceptor stream where the CN⎺ is captured and sent to an amperometric flow cell detector with a
silver-working electrode. In the presence of cyanide, silver electrode surface is oxidized at the applied
potential (E = 0,0 V vs. the reference electrode). The anodic current measured is proportional to the
app
concentration of cyanide in the standard or sample injected.
Calibrations and sample data are processed with the instrument's data acquisition software.
The user should be aware that the described method is operationally defined, the analytical protocol of
the standard has to be followed strictly to assure comparable results and the actual method conditions
used can affect the result obtained.
5 Interferences
5.1 Interferences by oxidizing agents
Oxidizing agents react with cyanide causing low results. The presence of oxidizing agents shall be
tested and treated, if present, just prior to pH adjustment for cyanide measurement.
5.2 Interferences by sulfide
Sulfide will diffuse through the gas diffusion membrane and can be detected in the amperometric
flow cell, causing the measurement to be biased high. Oxidized products of sulfide can also rapidly
convert CN⎺ to SCN⎺ at a high pH. A two-stage process is specified for sulfide removal. The initial lead
carbonate (6.9.4) addition treatment stage and filtration shall be carried out as soon as possible. The
sulfide removal and acidification reagent (6.8.14) is specified in this method. Its use will ensure removal
of sulfide interference up to 50 mg/l of sulfide. This shall be applied and analysis completed within 24 h
of taking the sample (see Clause 8).
NOTE In the absence of sulfide in the samples 0,1 mol/l HCl (6.2) as acidification as practiced in the original
USEPA method 1677 can also be used.
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ISO 22066:2020(E)

6 Reagents
WARNING — Cyanide solutions and wastes are toxic. Waste containing these substances shall
be removed appropriately. Perform work in a fume hood. Avoid contacting cyanides with acids
and aeration. Harmful if swallowed and if inhaled, very toxic to aquatic life with long lasting
effects. Handle carefully using personal protective equipment and dispose properly. Oxidation
of cyanide wastes is commonly used for cyanide waste detoxification. Calcium hypochlorite is
suitable at pH 10, using proper ventilation to capture any cyanogen chloride generated.
Use only reagents of recognized analytical grade.
6.1 Water, grade 1, as specified in ISO 3696.
6.2 Sodium hydroxide solution I, acceptor solution, c(NaOH) = 0,1 mol/l.
6.3 Sodium hydroxide solution II, c(NaOH) = 1,0 mol/l.
6.4 Sodium hydroxide solution III, c(NaOH) = 0,01 mol/l.
6.5 Potassium cyanide, KCN.
6.5.1 Potassium cyanide solution, KCN, ρ(CN) = 1 000 mg/l, (see Annex B).
Dissolve (2 503 ± 1) mg of potassium cyanide, KCN, (6.5), in sodium hydroxide solution III (6.4) in a
1 000 ml graduated flask and make up to volume with sodium hydroxide solution III (6.4). Sodium
cyanide (1 884 mg) may be substituted for potassium cyanide for stock solution preparation.
This solution is stable for six months at (5 ± 3) °C, if stored in the dark or brown bottles.
Alternatively, a potassium tetracyanozincate (2 380 mg/l) solution (6.6.1) may be used.
6.5.2 Cyanide solution I, ρ(CN) = 10 mg/l.
Pipette 1,00 ml of the potassium cyanide solution (6.5.1) in a 100 ml graduated flask and bring to
volume with sodium hydroxide solution III (6.4).
This solution is stable for one week at (5 ± 3) °C, if stored in the dark or brown bottles.
NOTE 1 Some laboratories substituted sodium cyanide for potassium cyanide for stock solution preparation
during the interlaboratory test for ISO 20950-1.
6.6 Potassium tetracyanozincate, K Zn(CN) .
2 4
6.6.1 Potassium tetracyanozincate solution, K Zn(CN) , ρ(CN) = (1 000 ± 2) mg/l, commercially
2 4
available.
This solution is stable for six months at (5 ± 3) °C, if stored in the dark.
6.6.2 Potassium tetracyanozincate solution I, ρ(CN) = 10 mg/l.
Pipette 1,00 ml of the potassium tetracyanozincate solution (6.6.1) in a 100 ml graduated flask and
bring to volume with sodium hydroxide solution III (6.4).
This solution is stable for one week at (5 ± 3) °C, if stored in the dark or brown bottles.
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ISO 22066:2020(E)

6.7 Calibration solutions
Prepare five to ten calibration solutions with cyanide concentrations, equidistantly distributed
over the working range, either by appropriate dilution of the cyanide solution I (6.5.2) or potassium
tetracyanozincate solution I (6.6.2).
If, for example, six calibration solutions should be prepared to cover the range of 5 µg/l to 50 µg/l,
proceed as follows:
Pipette 25 ml of the cyanide solution I (6.5.2) or potassium tetracyanozincate solution I (6.6.2), in a
500 ml graduated flask and make up to volume with sodium hydroxide solution III (6.4). This solution
contains 0,5 mg/l cyanide.
Pipette, in 100 ml graduated flasks, 1 ml, 3 ml, 5 ml, 7 ml, 9 ml, and 10 ml, respectively, of the above
mentioned 0,5 mg/l cyanide solution and make up to volume with sodium hydroxide solution III (6.4).
These solutions contain nominally 5 µg/l, 15 µg/l, 25 µg/l, 35 µg/l, 45 µg/l, and 50 µg/l of cyanide,
respectively. Correct calibration solution concentrations based the concentration found on titration of
the potassium cyanide solution (6.5.1) or potassium tetracyanozincate solution (6.6.1) used, following
the procedure given in Annex B by multiplying the nominal value by ρ(CN)/1 000 and round to the
nearest µg/l. Or, for example, if six calibration solutions should be prepared to cover the range of 50 µg/l
to 500 µg/l proceed as follows:
Pipette 25 ml of the cyanide solution I (6.5.2) or potassium tetracyanozincate solution I (6.6.2), in a
50 ml graduated flask and make up to volume with sodium hydroxide solution III (6.4). This solution
contains 5 mg/l cyanide.
Pipette, in 100 ml graduated flasks, 1 ml, 3 ml, 5 ml, 7 ml, 9 ml, and 10 ml, respectively, of the above
mentioned 5 mg/l cyanide solution and make up to volume with sodium hydroxide solution III (6.4).
These solutions contain nominally 50 µg/l, 150 µg/l, 250 µg/l, 350 µg/l, 450 µg/l, and 500 µg/l of
cyanide, respectively. Correct calibration solution concentrations based the concentration found
on titration of the potassium cyanide solution (6.5.1), following the procedure given in Annex B by
multiplying the nominal value by ρ(CN)/1 000 and round to the nearest µg/l.
Use calibration solutions less than or equal to 500 µg/l for samples with cyanide concentrations
<500 µg/l.
6.8 Reagents for the determination of total cyanide
6.8.1 Ag/AgCl reference electrode filling solution.
Fill the reference electrode as recommended by the instrument manufacturer.
6.8.2 Bismuth nitrate pentahydrate, Bi(NO ) ·5H O.
3 3 2
6.8.3 Cyanide electrode stabilization solution, approximately 5 mg/l as CN⎺.
Pipette 500 µl of potassium cyanide solution (6.5.1) or potassium tetracyanozincate solution (6.6.1),
into a 100 ml volumetric flask containing 1,0 ml of sodium hydroxide solution I (6.2). Dilute to volume
with water (6.1).
This solution is stable for one week if stored at (5 ± 3) °C.
Lower cyanide concentrations can be used, provided the detector signal is near saturation and sharp,
repeatable peaks are produced.
6.8.4 Hypophosphorous acid, H PO , 50 % solution.
3 2
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ISO 22066:2020(E)

6.8.5 Iron(II) cyanide stock solution, ρ(CN) = 1 000 mg/l.
Weigh 0,270 5 g K Fe(CN) ·3H O (6.8.12) into a 100 ml volumetric flask. Place 1,0 ml of 1,00 mol/l NaOH
4 6 2
(see 6.3) in the flask and dilute to volume with water (6.1).
The solution shall be stored in an amber glass bottle under refrigeration at (5 ± 3) °C
6.8.6 Iron(II) cyanide intermediate solution, ρ(CN) = 100 mg/l,
Pipette 10,0 ml of the iron(II) cyanide stock solution (6.8.5) into a 100 ml volumetric flask containing
1,0 ml of 1,00 mol/l NaOH (6.3). Dilute to volume with water (6.1).
The solution shall be stored in an amber glass bottle under refrigeration at (5 ± 3) °C.
6.8.7 Iron(II) cyanide recovery solution, ρ(CN) = 100 µg/l.
Pipette 100 μl of iron(II) cyanide intermediate solution (6.8.6) into a 100 ml volumetric flask containing
1,0 ml of 1,00 mol/l NaOH (6.3). Dilute to volume with water (6.1). Prepare fresh daily.
6.8.8 Iron(III) cyanide stock solution, ρ(CN) = 1 000 mg/l.
Weigh 0,210 9 g of K Fe(CN) (6.8.11) in a 100 ml volumetric flask. Place 1,0 ml of 1,00 mol/l NaOH (6.3)
3 6
in the flask and dilute to volume with water (6.1).
The solution shall be stored in an amber glass bottle under refrigeration at (5 ± 3) °C.
6.8.9 Iron(III) cyanide intermediate solution, ρ(CN) = 100 mg/l.
Pipette 10,0 ml of the iron(III) cyanide stock solution (6.8.8) into a 100 ml volumetric flask containing
1,0 ml of 1,00 mol/l NaOH (6.3). Dilute to volume with water (6.1).
The solution shall be stored in an amber glass bottle under refrigeration at (5 ± 3) °C.
6.8.10 Iron(III) cyanide recovery solution, ρ(CN) = 100 µg/l.
Pipette 100 μl of iron(III) cyanide intermediate solution (6.8.9) into a 100 ml volumetric flask containing
1,0 ml of 1,00 mol/l NaOH (6.3). Dilute to volume with water. Prepare fresh daily.
6.8.11 Potassium hexacyanoferrate(III), K Fe(CN)
3 6
6.8.12 Potassium hexacyanoferrate(II) trihydrate, K Fe(CN) ·3H O.
4 6 2
6.8.13 Sulfuric acid (I), ρ = 1,84 g/ml, mass fraction 95 % to 97 %.
6.8.14 Sulfide removal and acidification reagent.
Add 55 ml of water (6.1), to a 500 ml beaker, then carefully add 55 ml of concentrated sulfuric
acid (6.8.13) to the beaker. Weigh 1 g of bismuth nitrate pentahydrate, Bi(NO ) ·5H O (6.8.2) and add it
3 3 2
to the 500 ml beaker. Gently, stir the beaker until the bismuth nitrate pentahydrate has dissolved in the
acid solution. Carefully, add approximately 250 ml of water (6.1) to the beaker with stirring and allow
to cool. Then quantitatively transfer the beaker contents to a 1 l volumetric flask and fill to volume with
water (6.1).
CAUTION — This is an exothermic reaction and the solution will become hot during preparation.
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ISO 22066:2020(E)

6.8.15 Total acid reagent.
Carefully add 55 ml of concentrated sulfuric acid (6.8.13) to about 800 ml of water (6.1) in a 1 000 ml
volumetric flask. Cool to room temperature and add 20 ml of hypophosphorous acid (6.8.4). Dilute to
volume and mix.
WARNING — This is an exothermic reaction and the solution will become hot when preparing
this solution. Use this solution within 48 h of preparation.
6.9 Reagents for sample pre-treatment and preservation
6.9.1 Sodium acetate trihydrate, NaC H O ·3H O.
2 3 2 2
6.9.2 Acetic acid, CH COOH.
3
6.9.3 Acetate buffer.
Dissolve 410 g of sodium acetate trihydrate (6.9.1) in 500 ml of water (6.1). Add acetic acid (approximately
500 ml) (6.9.2) to yield a pH of 4,5.
6.9.4 Lead carbonate, PbCO , powder.
3
Dissolve into a concentrated solution prior to use.
DANGER — Harmful if swallowed or if inhaled, may cause cancer, may damage fertility or the
unborn child, may cause damage to organs through prolonged or repeated exposure, very toxic
to aquatic life with long lasting effects. Handle carefully using personal protective equipment
and dispose properly.
6.9.5 Lead acetate test paper, commercially available.
6.9.6 Sodium arsenite, NaAsO , powder.
2
DANGER — Fatal if swallowed or in contact with skin; toxic if inhaled; may cause cancer;
very toxic to aquatic life with long lasting effects. Handle carefully using personal protective
equipment and dispose properly.
6.9.6.1 Sodium arsenite solution, 5 g/l.
Dissolve 0,5 g sodium arsenate on 100 ml of water.
6.9.7 Potassium iodide starch test paper, commercially available.
7 Apparatus
7.1 Segmented flow analysis system.
A suitable example of the system is shown in Figure A.1. Alternative systems are also applicable if the
requirements in Clause 9 are achieved.
7.1.1 Autosampler or another device, allowing a reproducible introduction of the sample.
7.1.2 Reagent reservoirs.
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ISO 22066:2020(E)

7.1.3 Low pulsation pump, with specific chemically inert pump tubes, for flow rates as shown in
Table 1 as an example.
7.1.4 Gas diffusion cell, with hydrophobic semipermeable membrane from e.g. polypropylene or
2
PTFE, typical thickness 90 µm to 200 µm, pore size 0,1 µm to 1 µm, and minimum area of 150 mm in
contact with acceptor solution.
The gas diffusion membrane should be replaced when the baseline becomes noisy, or every one to
two weeks.
7.1.5 UV digester, with a 312 nm lamp and UV transparent digestion coil.
7.1.6 Manifold with highly reproducible dosing of sample and reagents, with appropriate
transport systems and connection assemblies made of chemically inert polymers.
7.1.7 Amperometric detector, with flow cell, to include a silver working electrode, a Ag/AgCl
reference electrode, and a Pt or stainless steel counter electrode.
7.1.8 Recording unit, for example strip chart recorder, integrator or printer/plotter.
As an example, instrument settings are shown in Table 1. In general, signal peak height is measured.
Use the computer hardware and software recommended by the instrument manufacturer to control
the apparatus and to collect data from the detector.
7.2 Additional apparatus, materials and measuring device.
7.2.1 Syringe membrane filter assembly, with membrane filters, pore size 0,45 µm.
7.2.2 pH meter and electrode, capable of measuring ±0,1 pH units.
8 Sampling and sample preparation
8.1 Oxidizing agent
Acidify KI starch paper (6.9.7) by moistening with acetate buffer (6.9.3). Add a drop of the sample to the
test paper as soon as the sample is collected; a blue color indicates the need for treatment. If oxidizing
agents are present, add powdered or recommended concentrated solution of sodium arsenite (6.9.6)
equivalent to 0,1 g/l sample to the sample to avoid degradation of cyanide and mix well. Repeat this
test until a drop of tr
...