Water quality - Determination of total cyanide and free cyanide using flow analysis (FIA and CFA) - Part 2: Method using continuous flow analysis (CFA) (ISO 14403-2:2012)

ISO 14403-2:2012 specifies methods for the determination of cyanide in various types of water (such as ground, drinking, surface, leachate, and waste water) with cyanide concentrations usually from 2 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 diluting the original sample or changing the pathlength of the flow cell.
In this method, a suitable mass concentration range from10 µg/l to 100 µg/l is described.
Seawater can be analysed with possible changes in sensitivity and adaptation of the reagent and calibration solutions to the salinity of the samples.

Wasserbeschaffenheit - Bestimmung von Gesamtcyanid und freiem Cyanid mittels Fließanalytik (FIA und CFA) - Teil 2: Verfahren der kontinuierlichen Durchflussanalyse (CFA) (ISO 14403-2:2012)

Dieser Teil von ISO 14403 legt Verfahren für die Bestimmung von Cyaniden in verschiedenen Wässern (wie
z. B. Grund-, Trink-, Oberflächen-, Sicker- und Abwasser) mit Cyanid-Konzentrationen von üblicherweise
2 µg/l bis 500 µg/l fest, die als Cyanid-Ionen in der unverdünnten Probe angegeben werden. Der
Einsatzbereich kann durch Änderung der Durchführungsbedingungen angepasst werden, z. B. durch
Verdünnen der ursprünglichen Probe oder Änderung der Weglänge der Durchflussküvette.
Der in diesem Teil von ISO 14403 beschriebene geeignete Massenkonzentrationsbereich beträgt 10 µg/l bis
100 µg/l.
Meerwasser kann nach Anpassung von Reagenz- und Bezugslösungen (Kalibrierlösungen) an den Salzgehalt
der Proben sowie mit möglichen Änderungen in der Empfindlichkeit analysiert werden.

Qualité de l'eau - Dosage des cyanures totaux et des cyanures libres par analyse en flux (FIA et CFA) - Partie 2: Méthode par analyse en flux continu (CFA) (ISO 14403-2:2012)

L'ISO 14403-2:2012 spécifie des méthodes pour le dosage des cyanures présents dans divers types d'eau (tels qu'eau souterraine, eau potable, eau de surface, lixiviat et eau résiduaire) en concentrations généralement comprises entre 2 µg/l et 500 µg/l, exprimées en ions cyanure dans l'échantillon non dilué. La gamme d'application peut être modifiée en faisant varier les conditions opératoires, par exemple en diluant l'échantillon d'origine ou en modifiant la longueur du trajet de la cellule de mesure.
La présente méthode décrit une gamme appropriée de concentrations en masse allant de 10 µg/l à 100 µg/l.
L'eau de mer peut être analysée avec des changements de sensibilité et l'adaptation des réactifs et des solutions d'étalonnage à la salinité des échantillons.

Kakovost vode - Določevanje celotnega in prostega cianida s pretočno analizo (FIA in CFA) - 2. del: Metoda s kontinuirano pretočno analizo (CFA) (ISO 14403-2:2012)

Ta del standarda ISO 14403 opisuje metode za določevanje cianida v različnih vrstah vode (na primer podtalni, pitni, površinski, izcedni in odpadni vodi) z običajnimi koncentracijami cianida od 2 µg/l do 500 µg/l, izraženimi s cianidnimi ioni v nerazredčenem vzorcu. Območje uporabe se lahko spremeni s spreminjanjem operativnih pogojev, npr. z redčenjem izvornega vzorca ali s spremembo dolžine poti pretočne celice. V tej metodi je opisano primerno območje masne koncentracije od 10 μg/l do 100 μg/l. Morska voda se lahko analizira z možnimi spremembami občutljivosti ter prilagajanjem raztopin reagenta in raztopin za kalibracijo slanosti vzorcev.

General Information

Status
Published
Publication Date
14-Jul-2012
Current Stage
6060 - Definitive text made available (DAV) - Publishing
Due Date
15-Jul-2012
Completion Date
15-Jul-2012

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SLOVENSKI STANDARD
SIST EN ISO 14403-2:2013
01-januar-2013
1DGRPHãþD
SIST EN ISO 14403:2003
.DNRYRVWYRGH'RORþHYDQMHFHORWQHJDLQSURVWHJDFLDQLGDVSUHWRþQRDQDOL]R
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Water quality - Determination of total cyanide and free cyanide using flow analysis (FIA

and CFA) - Part 2: Method using continuous flow analysis (CFA) (ISO 14403-2:2012)

Wasserbeschaffenheit - Bestimmung von Gesamtcyanid und freiem Cyanid mittels

Fließanalytik (FIA und CFA) - Teil 2: Verfahren der kontinuierlichen Durchflussanalyse

(CFA) (ISO 14403-2:2012)

Qualité de l'eau - Dosage des cyanures totaux et des cyanures libres par analyse en flux

(FIA et CFA) - Partie 2: Méthode par analyse en flux continu (CFA) (ISO 14403-2:2012)

Ta slovenski standard je istoveten z: EN ISO 14403-2:2012
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST EN ISO 14403-2:2013 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 14403-2:2013
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SIST EN ISO 14403-2:2013
EUROPEAN STANDARD
EN ISO 14403-2
NORME EUROPÉENNE
EUROPÄISCHE NORM
July 2012
ICS 13.060.50 Supersedes EN ISO 14403:2002
English Version
Water quality - Determination of total cyanide and free cyanide
using flow analysis (FIA and CFA) - Part 2: Method using
continuous flow analysis (CFA) (ISO 14403-2:2012)

Qualité de l'eau - Dosage des cyanures totaux et des Wasserbeschaffenheit - Bestimmung von Gesamtcyanid

cyanures libres par analyse en flux continu (FIA et CFA) - und freiem Cyanid mittels Fließanalytik (FIA und CFA) - Teil

Partie 2: Méthode par analyse en flux continu (CFA) (ISO 2: Verfahren der kontinuierlichen Durchflussanalyse (CFA)

14403-2:2012) (ISO 14403-2:2012)
This European Standard was approved by CEN on 13 July 2012.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European

Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national

standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.

This European Standard exists in three official versions (English, French, German). A version in any other language made by translation

under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same

status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,

Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United

Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels

© 2012 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 14403-2:2012: E

worldwide for CEN national Members.
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SIST EN ISO 14403-2:2013
EN ISO 14403-2:2012 (E)
Contents Page

Foreword ..............................................................................................................................................................3

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SIST EN ISO 14403-2:2013
EN ISO 14403-2:2012 (E)
Foreword

This document (EN ISO 14403-2:2012) has been prepared by Technical Committee ISO/TC 147 "Water

quality" in collaboration with Technical Committee CEN/TC 230 “Water analysis” the secretariat of which is

held by DIN.

This European Standard shall be given the status of a national standard, either by publication of an identical

text or by endorsement, at the latest by January 2013, and conflicting national standards shall be withdrawn at

the latest by January 2013.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.

This document supersedes EN ISO 14403:2002.

According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following

countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech

Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece,

Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,

Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom.

Endorsement notice

The text of ISO 14403-2:2012 has been approved by CEN as a EN ISO 14403-2:2012 without any

modification.
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SIST EN ISO 14403-2:2013
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SIST EN ISO 14403-2:2013
INTERNATIONAL ISO
STANDARD 14403-2
First edition
2012-07-15
Water quality — Determination of total
cyanide and free cyanide using flow
analysis (FIA and CFA) —
Part 2:
Method using continuous flow analysis
(CFA)
Qualité de l’eau — Dosage des cyanures totaux et des cyanures libres
par analyse en flux (FIA et CFA) —
Partie 2: Méthode par analyse en flux continu (CFA)
Reference number
ISO 14403-2:2012(E)
ISO 2012
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2012

All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means,

electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISO’s

member body in the country of the requester.
ISO copyright office
Case postale 56 • CH-1211 Geneva 20
Tel. + 41 22 749 01 11
Fax + 41 22 749 09 47
E-mail copyright@iso.org
Web www.iso.org
Published in Switzerland
ii © ISO 2012 – All rights reserved
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(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, sulfite, nitrite and carbonyl compounds ........................................................ 2

4.3 Other interferences ............................................................................................................................................. 2

5 Principle ................................................................................................................................................................. 3

5.1 Determination of total cyanide ......................................................................................................................... 3

5.2 Determination of free cyanide .......................................................................................................................... 3

6 Reagents ................................................................................................................................................................ 3

7 Apparatus .............................................................................................................................................................. 6

8 Sampling and sample preparation .................................................................................................................. 8

9 Procedure .............................................................................................................................................................. 9

9.1 Flow system set-up ............................................................................................................................................. 9

9.2 Reagent blank measurement ........................................................................................................................... 9

9.3 Checking the suitability of the flow system ...............................................................................................10

9.4 Calibration ...........................................................................................................................................................10

9.5 Sample measurement ....................................................................................................................................... 11

10 Calculation .......................................................................................................................................................... 11

11 Expression of results ....................................................................................................................................... 11

12 Test report ........................................................................................................................................................... 11

Annex A (informative) Examples of flow systems ...................................................................................................13

Annex B (normative) Determination of the real cyanide concentration in the potassium

cyanide solution ................................................................................................................................................16

Annex C (informative) Example for the determination of total cyanide and free cyanide by continuous

flow analysis (CFA) with gas diffusion and amperometric detection .................................................17

Annex D (informative) Performance data ...................................................................................................................19

Bibliography .....................................................................................................................................................................21

© ISO 2012 – All rights reserved iii
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
Foreword

ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies

(ISO member bodies). The work of preparing International Standards is normally carried out through ISO

technical committees. Each member body interested in a subject for which a technical committee has been

established has the right to be represented on that committee. International organizations, governmental and

non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International

Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.

International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.

The main task of technical committees is to prepare International Standards. Draft International Standards

adopted by the technical committees are circulated to the member bodies for voting. Publication as an

International Standard requires approval by at least 75 % of the member bodies casting a vote.

Attention is drawn to the possibility that some of the elements of this document may be the subject of patent

rights. ISO shall not be held responsible for identifying any or all such patent rights.

ISO 14403-2 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,

chemical and biochemical methods.

This first edition of ISO 14403-2 cancels and replaces ISO 14403:2002, which has been technically revised.

ISO 14403 consists of the following parts, under the general title Water quality — Determination of total cyanide

and free cyanide using flow analysis (FIA and CFA):
— Part 1: Method using flow injection analysis (FIA)
— Part 2: Method using continuous flow analysis (CFA)
iv © ISO 2012 – All rights reserved
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
Introduction

Methods using flow analysis automate wet chemical procedures and are particularly suitable for the processing

of many analytes in water in large series of samples at a high frequency of analysis.

Analysis can be performed by flow injection analysis (FIA) or continuous flow analysis (CFA). Both methods

share the feature of an automatic introduction of the sample into a flow system (manifold) in which the analytes

in the sample react with reagent solutions on their way through the manifold. Sample preparation may be

integrated in the manifold. The reaction product is measured in a flow detector (e.g. flow photometer).

See the foreword for a list of parts of this International Standard.

It should be investigated whether and to what extent particular problems require the specification of additional

marginal conditions.
© ISO 2012 – All rights reserved v
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SIST EN ISO 14403-2:2013
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SIST EN ISO 14403-2:2013
INTERNATIONAL STANDARD ISO 14403-2:2012(E)
Water quality — Determination of total cyanide and free cyanide
using flow analysis (FIA and CFA) —
Part 2:
Method using continuous flow analysis (CFA)

WARNING — Persons using this part of ISO 14403 should be familiar with normal laboratory practice.

This part of ISO 14403 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.

IMPORTANT — It is absolutely essential that tests conducted according to this part of ISO 14403 be

carried out by suitably trained staff.
1 Scope

This part of ISO 14403 specifies methods for the determination of cyanide in various types of water (such

as ground, drinking, surface, leachate, and waste water) with cyanide concentrations usually from 2 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 diluting the original sample or changing the pathlength of the flow cell.

In this method, a suitable mass concentration range from10 µg/l to 100 µg/l is described.

Seawater can be analysed with possible changes in sensitivity and adaptation of the reagent and calibration

solutions to the salinity of the samples.
2 Normative references

The following referenced documents are indispensable for the application 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 and 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 purpose of this part of ISO 14403, the following definitions apply:
3.1
free cyanide
easily liberatable cyanide

sum of cyanide ions and the cyanide bound in weak metal cyanide complexes that liberate HCN at pH 3,8

© ISO 2012 – All rights reserved 1
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
3.2
total cyanide

free cyanide (3.1), and in addition stronger metal–cyanide complex compounds, with the exception of cyanide

bound in gold, cobalt, platinum, ruthenium, and rhodium complexes, from which recovery can be partial

NOTE 1 Thiocyanate, organically bound cyanide and cyanate are not included in this definition of total cyanide.

NOTE 2 Distillation methods may recover some organic cyanide. Use the diffusion method when organic cyanide

complexes are suspected to be present.
4 Interferences
4.1 Interferences by oxidizing agents

Oxidizing agents such as chlorine decompose most of the cyanides. If the presence of oxidizing agents cannot

be excluded, treat the sample immediately after sampling. Test a drop of the sample with potassium iodide-

starch test paper (KI starch paper); a blue colour indicates the need for treatment. Add sodium thiosulfate, a

few crystals at a time, until a drop of sample produces no colour on the indicator paper. Then add an additional

portion of 0,6 g of ascorbic acid (6.9) for each 1 000 ml of sample volume.
Do not add ascorbic acid unless samples will be analysed within 24 h.
4.2 Interferences by sulfide, sulfite, nitrite and carbonyl compounds

Interferences by sulfide start at 100 mg/l. It affects the colorimetric procedure, especially the gas diffusion

method, and the amperometric procedure (see Annex C). If a drop of the sample on lead acetate test paper

indicates the presence of sulfide, treat an additional 25 ml of the stabilized sample (pH >12) to that required for

the cyanide determination with powdered lead carbonate.
Lead sulfide precipitates if the sample contains sulfide.

Repeat this operation until a drop of the treated sample solution does not darken the lead acetate test paper.

Filter the solution through a dry filter paper into a dry beaker, and from the filtrate measure the sample to be

used for analysis. Avoid a large excess of lead and a long contact time in order to minimize loss by complexation

or occlusion of cyanide on the precipitated material.

If the amperometric method (Annex C) is applied, it is necessary systematically to add lead carbonate to samples

during the analysis (a few milligrams for a 10 ml sample), followed by filtration or decantation performed before

the filtered sample aliquot is placed on the sample tray of the continuous flow analyser.

Aldehydes and ketones can, under certain conditions, absorb cyanide by nucleophilic addition. To avoid this

interference ethylenediamine can be added to the sample.

Under the given distillation conditions, aldehydes can transform cyanide to nitrite. Aldehydes can be removed

by adding silver nitrate to the sample. The addition of AgNO can alter the ratio of the concentrations of free

and total cyanide. The user should evaluate this procedure.

Interference by nitrite above concentrations of 5 mg/l can be avoided by addition of sulfamic acid (6.10) to the

buffer (pH 3,8) for the distillation and gas diffusion method (6.21.1).
Sulfite interferes above concentrations of 1 mg/l.
4.3 Other interferences

Samples containing particulate matter can lead to losses if the particles clog the transport tubes and are

not transported completely into the UV unit. This effect can be minimized by homogenizing (e.g. stirring) the

sample immediately prior to analysis to ensure that a representative sample is taken and to reduce the particle

size. Remaining particles with diameters >0,1 mm should be removed by filtration.

2 © ISO 2012 – All rights reserved
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)

When using in-line distillation for separation of the hydrogen cyanide, salt concentrations higher than 10 g/l

of salts can cause clogging of the distillation coil. Dilute these samples prior to measurement or use a gas

diffusion method in order to overcome this problem.

Thiocyanate can slightly interfere and lead to positive bias (9.3.2). Significant interferences can arise from

cyanide impurities in thiocyanate or from inappropriate distillation procedures (7.1).

5 Principle
5.1 Determination of total cyanide

Complex-bound cyanide is decomposed by UV light at pH 3,8. An UV-B lamp (312 nm to 400 nm) and a

digestion coil of borosilicate glass, quartz glass or polytetrafluorethylene (PTFE) is used. The UV unit shall

ensure that UV light with a wavelength of <290 nm is filtered off thus preventing the conversion of thiocyanate

into cyanide.

The hydrogen cyanide present at pH 3,8 is separated by online distillation at 125 °C or by gas diffusion at 30 °C

to 40 °C across a hydrophobic membrane. Using gas diffusion, hydrogen cyanide is absorbed in a sodium

hydroxide solution.

The hydrogen cyanide is then determined photometrically by the reaction of cyanide with chloramine-T to

cyanogen chloride. This reacts with pyridine-4-carboxylic acid and 1,3-dimethylbarbituric acid to give a red dye

whose absorption is proportional to cyanide concentration.
5.2 Determination of free cyanide

During the procedure specified in 5.1, the UV-B lamp is switched off when determining the free cyanide content.

During distillation at pH 3,8 for separation of the hydrogen cyanide present, a zinc sulfate solution is added to

the sample flow in order to precipitate any iron cyanides present as the zinc-cyanoferrate complex.

When using the gas diffusion method for the liberation of cyanide from the nickel complex, 50 µl

tetraethylenepentamine solution (6.12) per 30 ml sample is added prior to the analysis (see Reference [11]).

For detection see 5.1.

Alternatively, free and total cyanide can be determined after gas diffusion using an amperometric detector

(see Annex C).
6 Reagents

WARNING — KCN, K Zn(CN) , their solutions, and wastes are toxic. Waste containing these substances

2 4
shall be removed appropriately.
Use only reagents of recognized analytical grade.

Smaller portions of the following solutions can be applied provided the ratios of the prescribed volumes and

mass concentrations are maintained.
6.1 Water, grade 1, as defined in ISO 3696.
6.2 Hydrochloric acid, c(HCl) = 1 mol/l.
6.3 Sodium hydroxide solution I, c(NaOH) = 0,4 mol/l.
6.4 Sodium hydroxide solution II, c(NaOH) = 1,0 mol/l.
6.5 Sodium hydroxide solution III, c(NaOH) = 0,2 mol/l.
© ISO 2012 – All rights reserved 3
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
6.6 Sodium hydroxide solution IV, rinsing solution, c(NaOH) = 0,01 mol/l.
6.7 Surfactant, polyoxyethylene laurylether, HO-(CH CH -O) -C H .
2 2 n 18 37

Add 30 g of polyoxyethylene laurylether in small quantities to 100 ml of water (6.1) and mix well.

Alternatively use a commercially available solution of the surfactant.
6.8 Citric acid monohydrate, C H O⋅H O.
6 8 7 2
6.9 Ascorbic acid, C H O .
6 8 6
6.10 Sulfamic acid, H SO N.
3 3
6.11 Tetraethylenepentamine, C H N .
8 23 5
6.12 Tetraethylenepentamine solution (for free cyanide only).
Dissolve 0,75 g of tetraethylenepentamine (6.11) in 250 ml of water.
This solution is stable for 1 month if stored at room temperature.
6.13 Zinc sulfate heptahydrate, ZnSO⋅7H O.
4 2
6.14 Potassium hydrogenphthalate, KHC H O .
8 4 4
6.15 Chloramine-T trihydrate, C H ClNNaO S⋅3H O.
7 7 2 2
6.16 1,3-Dimethylbarbituric acid, C H N O .
6 8 2 3
6.17 Pyridine-4-carboxylic acid, C H NO .
6 5 2
6.18 Potassium thiocyanate, KSCN.
6.19 Potassium hexacyanoferrate(III), K Fe(CN) .
3 6
6.20 Cyanide standards.
6.20.1 Potassium cyanide, KCN.
6.20.2 Potassium cyanide solution, KCN, ρ = 1 000 mg/l, (see Annex B).

Dissolve 2 500 mg ± 1 mg of potassium cyanide, KCN (6.20.1), in sodium hydroxide solution IV (6.6) in a

1 000 ml volumetric flask, and make up to volume with sodium hydroxide solution IV (6.6).

A commercially available and certified 1 000 mg/l KCN stock solution may be used.

The solution is stable for 3 months at 1 °C to 8 °C.
Alternatively, a potassium tetracyanozincate solution (6.20.3) can be used:

6.20.3 Potassium tetracyanozincate solution, K Zn(CN) , ρ = 1 000 mg/l ± 2 mg/l, commercially available.

2 4 CN
The solution is stable for 3 months at 1 °C to 8 °C.
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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
6.20.4 Cyanide solution I, ρ = 10 mg/l.

Pipette 1 ml of the potassium tetracyanozincate solution I (6.20.3) or 1 ml of the potassium cyanide solution

(6.20.2) into a 100 ml volumetric flask, and make up to volume with sodium hydroxide solution IV (6.6).

This solution is stable for 1 week if stored at 1 °C to 8 °C.
6.20.5 Calibration solutions

Prepare at least five calibration solutions with cyanide concentrations, roughly regularly distributed over the

working range, by appropriate dilution of the cyanide solution I (6.20.4). If, for example, six calibration standards

should be prepared, proceed as follows.

Pipette 10 ml of the cyanide solution I (6.20.4) into a 100 ml volumetric flask, and make up to volume with

sodium hydroxide solution IV (6.6). This solution contains 1mg/l cyanide.

Pipette, into 100 ml volumetric flasks, 1 ml, 3 ml, 5 ml, 6 ml, 8 ml, or 10 ml, respectively, of the previously

mentioned 1 mg/l cyanide solution and make up to volume with sodium hydroxide solution IV (6.6).

These solutions contain 10 µg/l, 30 µg/l, 50 µg/l, 60 µg/l, 80 µg/l, and 100 µg/l of cyanide, respectively [except

for corrections in the concentration found on titration of the potassium cyanide solution (6.20.2), (see Annex B)].

These solutions are stable for 2 d if stored in a refrigerator at 1 °C to 5 °C.
6.21 Reagents for the determination of cyanide

6.21.1 Buffer, pH 3,8, for distillation and gas diffusion method (R1 in Figures A.1, A.2 and C.1).

Dissolve, in about 350 ml water (6.1), 10 g of citric acid (6.8). Add 50 ml of sodium hydroxide solution I (6.3) and,

if necessary, adjust to pH 3,8 with hydrochloric acid (6.2) or sodium hydroxide solution IV (6.6). Add 12,5 ml of

hydrochloric acid (6.2). Dilute to 500 ml with water.

NOTE Due to the addition of HCl, the pH of this buffer is about 3,4. After mixing with the sample a pH of 3,8 is achieved.

This solution is stable for 3 months if stored in a refrigerator at 1 °C to 5 °C.

6.21.2 Zinc sulfate solution, only for distillation method (R2 in Figure A.1).

Dissolve 10 g of zinc sulfate heptahydrate (6.13) in 750 ml of water (6.1), mix and dilute to 1 000 ml with water.

6.21.3 Recipient solution, only for gas diffusion (R3 in Figure A.2).
Sodium hydroxide solution III (6.5).

6.21.4 Buffer solutions for the final photometric determination (R4 in Figures A.1 and A.2)

6.21.4.1 For the distillation method (R4a in Figure A.1).

Dissolve 2,3 g of sodium hydroxide (NaOH) in 500 ml of water. Add 20,5 g of potassium hydrogenphthalate

(6.14) and dilute to approximately 975 ml with water.

If necessary, adjust the pH of the solution to 5,2 with hydrochloric acid (6.2) or sodium hydroxide solution II (6.4).

Add 1 ml of surfactant (6.7) and make up to 1 000 ml with water.

For best results this solution is stable for 1 month if stored in an amber bottle in a refrigerator at 1 °C to 5 °C.

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SIST EN ISO 14403-2:2013
ISO 14403-2:2012(E)
6.21.4.2 For the gas diffusion method (R4b in Figure A.2):

Dissolve 7,0 g of sodium hydroxide (NaOH) in 250 ml of water. Add 35,4 g of succinic acid (6.24) and dilute to

500 ml with water.

The solution has a pH of approximately 4.3. When mixed with sodium hydroxide solution I (6.21.3; R3 in

Figure A.2), a pH of 5,2 shall be achieved.

For best results this solution is stable for 1 month if stored in an amber bottle in a refrigerator at 1 °C to 5 °C.

6.21.5 Chloramine-T-trihydrate solution (R5 in Figures A.1 and A.2).
Dissolve 2,0 g ± 0,05 g of chloramine-T (6.15) in 1 000 ml of water.

This solution is stable for 1 week if stored in a refrigerator at 1 °C to 5 °C; however, for best results prepare

solution fresh daily.
6.21.6 Colour reagent (R6 in Figures A.1 and A.2).

Carefully dissolve in a 1 000 ml volumetric flask, 7,0 g of sodium hydroxide, NaOH, in about 500 ml of water

(6.1). Add 16,8 g ± 0,1 g of 1,3-dimethylbarbituric acid (6.16), and 13,6 g ± 0,1 g of pyridine-4-carboxylic acid

(6.17), and dilute to approximately 975 ml with water (6.1).

If necessary, adjust the solution to pH 5,2 with hydrochloric acid (6.2) or sodium hydroxide solution II (6.4).

Make up to 1 000 ml with water (6.1). Mix this solution intensively (e.g. by using a magnetic stirrer) for 1 h at

30 °C and then filter over a pleated filter (e.g. hardened ashless paper).
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