ISO 17690:2015

Water quality — Determination of available free cyanide (pH 6) using flow injection analysis (FIA), gas-diffusion and amperometric detection

ISO 17690:2015 specifies methods for the determination of available free cyanide at pH 6 in various types of water (such as ground, drinking, surface, leachate, waste water, and metallurgical processing waste water) with cyanide concentrations from 5 µg/l to 500 µg/l expressed as cyanide ions in the undiluted sample. The range of application can be changed by varying the operation conditions, e.g. by using a different injection volume.

Qualité de l'eau — Dosage des cyanures libres disponibles (pH 6) par analyse avec injection en flux (FIA), diffusion de gaz et détection ampérométrique

General Information

• Status: Published
• Publication Date: 05-Mar-2015
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: ISO/TC 147/SC 2 - Physical, chemical and biochemical methods
• Drafting Committee: ISO/TC 147/SC 2/WG 66 - Cyanide
• Current Stage: 9093 - International Standard confirmed
• Completion Date: 09-Jun-2020

Standards Content (Sample)

INTERNATIONAL ISO
STANDARD 17690
First edition
2015-03-15
Water quality — Determination of
available free cyanide (pH 6) using
flow injection analysis (FIA), gas-
diffusion and amperometric detection
Qualité de l’eau — Dosage des cyanures libres disponibles (pH 6)
par analyse avec injection en flux (FIA), diffusion de gaz et détection
ampérométrique
Reference number
ISO 17690:2015(E)
©
ISO 2015

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ISO 17690:2015(E)

COPYRIGHT PROTECTED DOCUMENT
© ISO 2015
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ISO 17690:2015(E)

Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Interferences . 2
4.1 Interferences by oxidizing agents . 2
4.2 Interferences by sulfide . 2
5 Principle . 2
6 Reagents . 2
7 Apparatus . 4
8 Sampling and sample preparation . 5
9 Procedure. 5
9.1 Flow system set up . 5
9.2 Reagent blank measurement . 6
9.3 Checking the suitability of the flow injection system . 6
9.3.1 Electrode stabilization . 6
9.3.2 Recovery rates . 6
9.4 Calibration . 7
9.5 Sample measurement . 7
10 Calculations. 7
11 Expression of results . 8
12 Test report . 8
Annex A (informative) Example of a flow injection system . 9
Annex B (normative) Determination of the real cyanide concentration in the potassium
cyanide solution (6.5.1).10
Annex C (informative) Performance data .11
Bibliography .12
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ISO 17690:2015(E)

Foreword
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bodies (ISO member bodies). The work of preparing International Standards is normally carried out
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The committee responsible for this document is ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods.
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ISO 17690:2015(E)

Introduction
Methods using flow analysis automate wet chemical procedures and 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 flow injection analysis (FIA) using the feature of an automatic dosage
of the sample into a flow system (manifold) where the analytes in the sample reacts with the reagent
solutions on their way through the manifold. The sample preparation can be integrated in the manifold.
The reaction product is measured by a flow detector (e.g. amperometer).
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INTERNATIONAL STANDARD ISO 17690:2015(E)
Water quality — Determination of available free cyanide
(pH 6) using flow injection analysis (FIA), gas-diffusion and
amperometric detection
WARNING — Persons using this International Standard should be familiar with the normal
laboratory practice. This International Standard 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 compliance with any national regulatory conditions
including neutralization and proper disposal of waste solutions.
IMPORTANT — It is absolutely essential that tests conducted in accordance with this International
Standard be carried out by suitably qualified staff.
1 Scope
This International Standard specifies methods for the determination of available free cyanide at pH 6
in various types of water (such as ground, drinking, surface, leachate, waste water, and metallurgical
processing waste water) with cyanide concentrations from 5 µg/l to 500 µg/l expressed as cyanide ions
in the undiluted sample. The range of application can be changed by varying the operation conditions,
e.g. by using a different injection volume (Figure A.1).
NOTE 1 ISO 2080:2008, 3.105, the concentration of available free cyanide as determined by a specified
analytical method.
NOTE 2 The detection limit for this method was determined by interlaboratory testing at the national level
using ASTM International D6512 Practice for Interlaboratory Quantitation Estimate.
NOTE 3 Free cyanides according to ISO 14403 and ISO 17690 are not equivalent.
In this method, two suitable mass concentration ranges from 5 µg/l to 50 µg/l and from 50 µg/l to
500 µg/l are described.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. 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
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
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ISO 17690:2015(E)

3.1
available free cyanide (pH 6)
sum of HCN, cyanide ions, and cyanide bound in the metal-cyano complexes that are easily dissociated
into HCN/CN¯ at the pH of 6 determined in accordance with this International Standard
4 Interferences
4.1 Interferences by oxidizing agents
Test for the presence of oxidizing agents. Acidify KI starch paper by moistening with acetate buffer (6.7.1).
Add a drop of the sample to the test paper as soon as the sample is collected; a blue colour indicates the
need for treatment. If oxidizing agents are present, add powdered sodium arsenite (6.9) (0,1 g/l sample)
to the sample to avoid degradation of cyanide and mix well. Repeat this test until a drop of treated
sample no longer produces a blue colour on the acidified KI starch test paper.
4.2 Interferences by sulfide
Sulfide will diffuse through the gas diffusion membrane and can be detected in the amperometric flow
cell. Oxidized products of sulfide can also rapidly convert CN¯ to SCN¯ at a high pH. Test for sulfide by
moistening lead acetate paper with acetate buffer solution (6.7.1) and then add a drop of sample on
the lead acetate paper. If the paper turns black, sulfide is present. Add powdered lead carbonate (6.8)
(0,1 g/l of sample). Repeat this test until a drop of treated sample no longer darkens the acidified lead
acetate test paper. The supernatant containing cyanide shall be filtered immediately to avoid the rapid
loss of cyanide due to the formation of thiocyanate.
Lead acetate test strips might not be sensitive enough to detect low levels of sulfide; therefore, treatment
should be performed on samples where sulfide is suspected. Interference can be confirmed by analysing the
sample with or without treatment. If the measured cyanide in the untreated sample is significantly higher
than in the treated sample, sulfide is likely present and treatment should be performed to remove sulfide.
5 Principle
The sample is introduced into a carrier solution of the flow injection analysis (FIA) system through an
injection valve and confluence downstream with a phosphate buffer solution at pH 6 to measure available
free 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 (Eapp = 0,0 V vs. the reference electrode). The anodic current measured
is proportional to the concentration of cyanide in the standard or sample injected.
Calibrations and sample data are processed with the instrument’s data acquisition software.
6 Reagents
WARNING — Cyanide solutions and wastes are toxic. Waste containing these substances shall be
removed appropriately.
Use only reagents of recognized analytical grade.
6.1 Water, grade 1, as defined in ISO 3696.
6.2 Sodium hydroxide solution I, acceptor solution, c = 0,1 mol/l.
(NaOH)
6.3 Sodium hydroxide solution II, c = 1,0 mol/l.
(NaOH)
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ISO 17690:2015(E)

6.4 Sodium hydroxide solution III, c = 0,01 mol/l.
(NaOH)
6.5 Potassium cyanide, KCN.
6.5.1 Potassium cyanide solution, KCN, ρ = 1 000 mg/l, (see Annex B).
(CN)
Dissolve 2 500 mg ± 1 mg of potassium cyanide, KCN, 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).
This solution is stable for six months at (5 ± 3) °C, if stored in the dark or brown bottles.
Alternatively, a potassium tetracyanozincate solution (6.6.1) can be used.
6.5.2 Cyanide solution I, ρ = 10 mg/l.
(CN)
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.
6.5.3 Calibration solutions.
Prepare at least five and up 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).
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) 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, or 10 ml, respectively, of the above
mentioned 0,5 mg/l cyanide solution
...