SIST EN ISO 10304-3:1998

Water quality - Determination of dissolved anions by liquid chromatography of ions - Part 3: Determination of chromate, iodide, sulfite, thiocyanate and thiosulfate (ISO 10304-3:1997)

The method is intended for monitoring waste water and the respective concentration of the anions mentioned in the title.

Wasserbeschaffenheit - Bestimmung der gelösten Anionen mittels Ionenchromatographie - Teil 3: Bestimmung von Chromat, Iodid, Sulfit, Thiocyanat und Thiosulfat (ISO 10304-3:1997)

Qualité de l'eau - Dosage des anions dissous par chromatographie des ions en phase liquide - Partie 3: Dosage des ions chromate, iodure, sulfite, thiocyanate et thiosulfate (ISO 10304-3:1997)

La présente partie de l'ISO 10304 spécifie des méthodes pour le dosage des anions dissous: -- iodure, thiocyanate et thiosulfate (article 4); -- sulfite (article 5); -- chromate (article 6). Un prétraitement approprié de l'échantillon (par exemple dilution) et l'emploi d'un détecteur conductimétrique (CD), d'un détecteur UV (UV) ou d'un détecteur ampérométrique (AD) rendent possible le dosage dans les domaines de travail donnés dans le tableau 1.

Kakovost vode - Določevanje raztopljenih anionov z ionsko kromatografijo - 3. del: Določevanje kromata, jodida, sulfita, tiocianita in tiosulfata (ISO 10304-3:1997)

General Information

• Status: Published
• Publication Date: 31-Dec-1997
• ICS: 13.060.50 - Examination of water for chemical substances
• Technical Committee: KAV - Water quality
• Current Stage: 6060 - National Implementation/Publication (Adopted Project)
• Start Date: 01-Jan-1998
• Due Date: 01-Jan-1998
• Completion Date: 01-Jan-1998
• Directive: 2014-01-3849 - Pravilnik o prvih meritvah in obratovalnem monitoringu odpadnih voda
• Directive: TP213 - Pravilnik o minimalnih higienskih zahtevah, ki jih morajo izpolnjevati kopališča in kopalna voda v bazenih
• Directive: TRRTP064 - Rules on initial measurements and operational monitoring of wastewater
• Ref Project: EN ISO 10304-3:1997 - Water quality - Determination of dissolved anions by liquid chromatography of ions - Part 3: Determination of chromate, iodide, sulfite, thiocyanate and thiosulfate (ISO 10304-3:1997)

Overview

EN ISO 10304-3:1997 specifies ion‑chromatographic methods for the determination of dissolved anions in aqueous samples - specifically chromate, iodide, sulfite, thiocyanate and thiosulfate. Published under ISO/TC 147 for water quality, this part of ISO 10304 is intended principally for waste water monitoring and provides procedures, detector options and working ranges to ensure repeatable, comparable results in environmental laboratories.

Key topics and technical requirements

• Scope and analytes: Procedures for iodide, thiocyanate and thiosulfate (clause 4), sulfite (clause 5) and chromate (clause 6).
• Separation principle: Liquid ion chromatography using a low‑capacity anion exchanger and aqueous eluents (salts of weak acids). Organic modifiers (e.g., 4‑hydroxybenzonitrile, methanol, acetonitrile) can improve elution and reduce peak tailing for polarizable ions.
• Detector options:
  • Conductivity detector (CD) - commonly combined with suppressors to lower eluent conductivity.
  • UV detector (UV) - direct or indirect absorbance (wavelengths noted in the standard).
  • Amperometric detector (AD) - measures oxidation current; operating voltage depends on eluent pH.
• Performance and calibration:
  • Column peak resolution minimum R = 1.3 for target analytes.
  • Calibration and evaluation of linear working range required (see ISO 8466‑1 referenced). Validation checks and replicate determinations are recommended.
• Working ranges (examples from standard): typical analyte working ranges span approximately 0.05–50 mg/l (chromate) and 0.1–50 mg/l (iodide, thiocyanate, thiosulfate, sulfite) depending on detector choice.
• Reagents & eluents: Uses analytical‑grade reagents and degassed water (conductivity < 0.01 mS/m). The standard gives example eluent recipes (e.g., sodium carbonate/sodium hydrogen carbonate concentrates with added 4‑hydroxybenzonitrile) and guidance on eluent storage and degassing.
• Quality and documentation: Clauses cover sampling, pretreatment, interferences, calculations, expression of results, precision, annexed interlaboratory data and bibliography.

Applications and users

• Environmental and wastewater laboratories conducting waste water monitoring, compliance testing and pollutant screening.
• Water utilities, industrial effluent monitoring, regulatory agencies and research institutions assessing anion contamination.
• Instrument vendors and method developers implementing or validating ion chromatography workflows for dissolved anions.

Related standards

• ISO 10304‑1, ISO 10304‑2, ISO 10304‑4 (other parts of the same series)
• ISO 5667 series (sampling guidance)
• ISO 8466‑1 (calibration and evaluation of analytical methods)

Keywords: EN ISO 10304‑3:1997, water quality, dissolved anions, ion chromatography, chromate, iodide, sulfite, thiocyanate, thiosulfate, wastewater monitoring, conductivity detector, UV detector, amperometric detector.

Standards Content (Sample)

SLOVENSKI STANDARD
01-januar-1998
.DNRYRVWYRGH'RORþHYDQMHUD]WRSOMHQLKDQLRQRY]LRQVNRNURPDWRJUDILMRGHO
'RORþHYDQMHNURPDWDMRGLGDVXOILWDWLRFLDQLWDLQWLRVXOIDWD,62
Water quality - Determination of dissolved anions by liquid chromatography of ions - Part
3: Determination of chromate, iodide, sulfite, thiocyanate and thiosulfate (ISO 10304-
3:1997)
Wasserbeschaffenheit - Bestimmung der gelösten Anionen mittels
Ionenchromatographie - Teil 3: Bestimmung von Chromat, Iodid, Sulfit, Thiocyanat und
Thiosulfat (ISO 10304-3:1997)
Qualité de l'eau - Dosage des anions dissous par chromatographie des ions en phase
liquide - Partie 3: Dosage des ions chromate, iodure, sulfite, thiocyanate et thiosulfate
(ISO 10304-3:1997)
Ta slovenski standard je istoveten z: EN ISO 10304-3:1997
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

INTERNATIONAL IS0
STANDARD 10304-3
First edition
1997-08- 15
Water quality -
Determination of dissolved
anions by liquid chromatography of ions -
Part 3:
Determination of chromate, iodide, sulfite,
thiocyanate and thiosulfate
Qua/it6 de I’eau - Dosage des anions dissous par chromatographie des ions
en phase liquide -
Parfie 3: Dosage des ions chromate, iodure, sulfite, thiocyanate et thiosulfate
Reference number
IS0 10304-3: 1997(E)
IS0 10304=3:1997(E)
Contents
1 Scope *.*.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
2 Normative references
3 Principle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*.
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
4 Determination of iodide, thiocyanate and thiosulfate
4.1 Reagents .
...............................................................................................................................................................................
4.2 Apparatus
..........................................................................................................................................................................
4.3 Interferences
................................................................................................................................... 9
4.4 Sampling and sample pretreatment
4.5 Procedure .
II
4.6 Calculation .
4.7 Expression of results .
4.8 Test report .
..............................................................................................................
5 Determination of sulfite
5.1 Reagents .
5.2 Apparatus .
5.3 Interferences .
5.4 Sampling and sample pretreatment .
5.5 Procedure .
.............................................................................................................................................................................
5.6 Calculation
............................................................................................................................................................
5.7 Expression of results
.............................................................................................................................................................................. 16
5.8 Test report
........................................................................................................ 16
6 Determination of chromate
6.1 Reagents .
6.2 Apparatus . 18
.......................................................................................................................................................................... 18
6.3 Interferences
................................................................................................................................... 18
6.4 Sampling and sample pretreatment
6.5 Procedure .
6.6 Calculation .
6.7 Expression of results .
6.8 Test report .
7 Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .~. 19
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. 20
Annex A (informative) Interlaboratory trials
Annex B (informative) Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .*. 22
0 IS0 1997
Unless otherwise specified, no part of this publication may be
All rights reserved.
reproduced or utilized in any form or by any means, electronic or mechanical, including
photocopying and microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
x.400 c=ch; a=400net; p=iso; o=isocs; s=central
Printed in Switzerland
ii
0 IS0
IS0 10304=3:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of national standards bodies (IS0
member bodies). The work of preparing International Standards is normally carried out through IS0 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. IS0 collaborates closely with the International Electrotechnical
Commission (IEC) on all matters of electrotechnical standardization.
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.
International Standard IS0 10304-3 was prepared by Technical Committee ISOITC 147, Water qualify, SC 2,
Physical, chemical and biochemical methods.
IS0 10304 consists of the following parts, under the general title Water quality - Determination of dissolved anions
by liquid chromatography of ions:
- Part I: Determination of fluoride, chloride, bromide, nitrate, nitrite, orfhophosphate and sulfate in water with
low contamination
- Part 2: Determination of bromide, chloride, nitrate, nitrite, orfhophosphate and sulfate in waste water
Par? 3: Determination of chromate, iodide, sulfite, thiocyana te and thiosulfa te
Part 4: Determination of chlorate, chloride and chlorite in water with low contamination
Annexes A and B of this part of IS0 10304 are for information only.

IS0 10304=3:1997(E) @ IS0
Introduction
The essential minimum requirements of an ion chromatographic system applied within the scope of this part of IS0 10304 are the
following:
a) Resolution of the column: For the anion to be determined it is essential that the
peak resolution does not fall below R= I,3 (4.2.2,
figure 3)
b) Method of detection: measurement of the electrical conductivity with or
1)
wi thout suppressor device
2) spectrometric measurement (UVnllS), directly or
indirectly
3) amperometric direct detection
c) Applicability of the method:
Working ranges according to table 1
d) Calibration (4.51): Calibration and determination of the linear working range
(see IS0 8466-l)
Guaranteeing the analytical quality: Validity check of the calibration function. Replicate
determinations if necessary.
The diversity of the appropriate and suitable assemblies procedural steps depending on them permit a description
only.
For further information on the analytical technique, see reference [I].

INTERNATIONAL STANDARD @ IS0 IS0 10304-3: 1997(E)
Water quality - Determination of dissolved anions by liquid chromatography of ions -
Part 3: Determination of chromate, iodide, sulfite, thiocyanate and thiosulfate
1 Scope
This part of IS0 10304 specifies methods for the determination in aqueous solution of the dissolved anions
- iodide, thiocyanate and thiosulfate (clause 4);
- sulfite (clause 5);
- chromate (clause 6).
An appropriate pretreatment of the sample (e.g. dilution) and the application of a conductivity detector (CD), UV detector
(UV) or amperometric detector (AD) make the working ranges given in table 1 feasible.
Table 1 - Applicable working ranges
Working range ‘) Detector
Anion
0,05 mg/l to 50 mg/l
Chromate (CrO,), clause 6 UV (h = 365 nm)
Iodide (I), clause 4 0,l mg/l to 50 mg/l CD or UV (h = 205 nm to 236 nm)
AD (approximately 0,7 V to I,1 V)
Sulfite (SO,), clause 5 0,l mg/l to 50 mg/l CD
0,5 mg/l to 50 mg/l UV (h = 205 nm to 220 nm)
Thiocyanate (SCN), clause 4 0,l mg/l to 50 mg/l
CD or UV (h = 205 nm to 220 nm)
AD (approximately 0,7 V to I,1 V)
Thiosulfate (S,O,), clause 4 0,l mg/l to 50 mg/l CD or UV (h = 205 nm to 220 nm)
AD (approximately 0,7 V to I,1 V)
‘) The working range is restricted by the exchange capacity of the columns. Dilute the sample into the working range if
necessary.
2 Normative references
The following standards contain provisions which, through reference in this text, constitute provisions of this part of IS0
10304. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the possibility of applying the most recent
editions of the standards indicated below. Members of IEC and IS0 maintain registers of currently valid International
Standards.
IS0 5667- 1: 1980 Water quality - Sampling - Part I: Guidance on the design of sampling
programmes.
IS0 5667-2:1991 Water quality - Sampling - Part 2: Guidance on sampling techniques.
IS0 5667-3: 1994 Water quality - Sampling - Part 3: Guidance on the preservation and handling of
samples.
IS0 8466-I:1990
Water quality - Calibration and evaluation of analytical methods and estimation of
performance characteristics -Part 7: Statistical evaluation of the linear calibration
function.
IS0 10304-I:1992
Water quality - Determination of dissolved fluoride, chloride, nitrite,
orthophosphate, bromide, nitrate, and sulfate ions, using liquid chromatography
of ions - Part 7: Method for water with low contamination.
IS0 10304-2: 1995 Water quality - Determination of dissolved anions by liquid chromatography of
ions - Part 2: Determination of bromide, chloride, nitrate, nitrite, orthophosphate
and sulfate in waste water.
IS0 10304-3: 1997(E) 0 IS0
3 Principle
3.1 Separation of ions is carried out by liquid chromatography using a separating column. A low capacity anion
exchanger is used as the stationary phase, and usually aqueous solutions of salts of weak monobasic and dibasic
acids as mobile phases (eluent, see 4.1.16, 5.1.4, 6.1.9).
3.2 The addition of organic agents, such as 4-hydroxybenzonitrile (see 4.1.16.2.2, 4.3.4), or organic solvents to the
eluent can be used to speed up the elution or reduce the tailing effects, especially for the analysis of the more
strongly polarizable ions iodide, thiocyanate and thiosulfate.
3.3 Detection is by conductivity (CD), UV and amperometric detectors (AD).
3.3.1 When using conductivity detectors it is essential that the eluents have a sufficiently low conductivity. For this
reason, conductivity detectors are often combined with suppressor devices (cation exchangers) which will reduce
the conductivity of the eluents and transform the sample species into their respective acids.
3.3.2 UV detection measures either the absorption directly (see table 1) or, in the case of anions which are
transparent in the UV-range, the decrease in the background absorption caused by a UV-absorbing eluent is
measured (indirect measurement). If indirect UV-detection is used, the measuring wavelength depends on the
composition of the eluent.
3.3.3 Amperometric detectors measure the quantity of current caused by the oxidation of anions. The oxidation
voltage required for the anions in question depends on the pH value of the eluent.
3.4 The concentration of the respective anions is determined by a calibration of the overall procedure. Particular
cases may require calibration by means of standard addition (spiking).
4 Determination of iodide, thiocyanate and thiosulfate
Follow the instructions given in clause 4 to make the working ranges given in table 1 feasible.
4.1 Reagents
Use only reagents of recognized analytical grade, if commercially available. Carry out weighing with an accuracy of 1% of
the nominal mass. The water shall have an electrical conductivity of < 0,Ol mS/m and shall not contain particulate matter
of a particle size > 0,45 pm. An increase of the electrical conductivity due to an uptake of carbon dioxide does not interfere
with the determination.
4.1.1 Sodium hydrogen carbonate, NaHCO,
4.1.2 Sodium carbonate, Na,CO,
4.1.3 Phthalic acid, C,H,O,
4.1.4 Disodium tetraborate, Na,B,O,
4.1.5 Gluconic acid, sodium salt, C,H,,NaO,
4.1.6 Methanol, CH,OH
4.1.7 Boric acid, H,BO,
4.1.8 Glycerol, C,H,O,
0 IS0
IS0 10304=3:1997(E)
4.1.9 Acetonitrile, CH,CN
4.1 .lO Sodium hydroxide solution, c( NaOH) = 0,l mol/l
4.1.11 4=hydroxybenzonitrile, C,H,NO
4.1.12 Tris(hydroxymethyl)aminomethane, C,H,,NO,
4.1.13 Sodium thiosulfate, pentahydrate, Na,S,O, , 5 H,O
4.1.14 Sodium iodide, Nal
4.1.15 Potassium thiocyanate, KSCN
4.1.16 Eluents
4.1.16.1 General
Different eluents are used, their choice depending on the type of separating column and detector. Therefore, follow the
column manufacturer’s. instructions for the exact composition of the eluent. The eluent compositions described in 4.1.16.2
and 4.1.16.3 are examples only.
A selection of reagents for some commonly used eluents is presented in 4.1.1 to 4.1.12.
Degas all eluents or prepare eluents using degassed water (4.1). Take steps to avoid any renewed gas pick-up during
operation (e.g. by helium superposition). In order to minimize the growth of bacteria or algae, store eluents in the dark and
renew every 2 to 3 days.
4.1.16.2 Examples of eluents for ion chromatography using the suppressor technique
F pressor te lchn ique, so Idium hydroxide and solutions of salts of weakly dissociated acid s, such
or the application of the
sup
car sodium hydrogen ca
a s sodium carbonate/sod ium hydrogen bonate, rbonate, and sodi urn tetraborate are used.
4.1.16.2.1 Sodium carbonate/sodium hydrogen carbonate concentrate
The addition of the following e luent concentrate to the sample has proved to be su ccessf u I for sample pret reatm ent and
see 4.1.16.2 .2).
eluent preparation (
- Place 36 g of sodium carbonate (4.1.2) and 36,l g of sodium hydrogen carbonate (4.1.1) in a graduated flask of
nominal capacity 1 000 ml, and dilute to volume with water (4.1).
The solution contai ns 0,34 mo l/l of sodium carbonate and 0,43 mol/l of sodium hydrogen carbonate. This solution is stable
4 “C to 6 “C.
for several months if stored at
4.1.16.2.2 Sodium carbonate/sodium hydrogen carbonate eluent
The following eluent has proved to be applicable for the determination of iodide, thiocyanate, thiosulfate:
- Place 50 ml of the concentrate (4.1.16.2.1) in a graduated flask of nominal capacity 5 000 ml, add water (4.1), add
750 mg of 4-hydroxybenzonitrile (4.1.11) and dilute to volume with water (4.1) ‘)‘).
The solution contains 0,0034 mol/l of sodium carbonate, 0,0043 mol/l of sodium hydrogen carbonate and 0,0013 mol/l of
4-hydroxybenzonitrile. Renew the eluent every 2 to 3 days (4.1.16).
The concentrations of iodide, thiocyanate and thiosulfate in these calibration solutions are 1 mg/l, 2 mg/l, 3 mg/l, 4 mg/l,
5 mg/l, 6 mg/l, 7 mg/l, 8 mg/l, 9 mg/l and 10 mg/l respectively.
Prepare the calibration solutions on the day of use.
I) 4-hydroxybenzonitrile can be added to speed up the elution or reduce the tailing effects, for the analysis of iodide, thiocyanate and
thiosulfate (4) but it can cause interferences with the determination of iodide, thiocyanate and thiosulfate when the UV detector is
used (4.3.4).
2) TO improve the solubility of 4-hydroxybenzonitrile the substance can be dissolved in a small quantity of methanol or ethanol and, after
addition to the eluent concentrate the solution should be stirred overnight.
IS0 10304=3:1997(E) 0 IS0
4.1.16.3 Examples of eluents for ion chromatography without using the suppressor technique
For ion chromatography without suppressor devices, use salt solutions, e.g. potassium hydrogenphthalate,
4-hydroxybenzoate, sodium borate/gIuconate, and sodium benzoate. The concentration of the salts is usually in the range
of 0,0005 to 0,Ol mol/l. Concentrate and eluent solutions are prepared as described in 4.1.16.2.1 or 4.1.16.2.2 respectively.
4.1.16.3.1 Phthalic acid concentrate
The addition of the following eluent concentrate to the sample has proved to be successful for sample pretreatment and
eluent preparation (see 4.1 J6.3.2).
- Place 4,485 g of phthalic acid (4.1.3) in a graduated flask of nominal capacity 1 000 ml, dissolve in approximately
800 ml of water (4.1), add 100 ml of acetonitrile (4.1.9) and dilute to volume with water (4.1). Adjust to a pH of 4
with tris(hydroxymethyl)aminomethane (4.1.12; can be added either in solid form or as solution, e.g. 1 mol/l).
The solution contains 0,027 mol/l phthalic acid and approximately 10 % of acetonitrile.
4.1.16.3.2 Phthalic acid eluent
The following eluent can be used for the determination of iodide, thiocyanate and thiosulfate:
- Pipette 100 ml of the concentrate (4.1.16.3.1) into a graduated flask of nominal capacity 1 000 ml and dilute to
volume with water (4.1).
The solution contains 0,0027 mol/l of phthalic acid and approximately 1 % of acetonitrile. The pH of the solution should be
in the range of 4,0 to 4,5 3, . Renew the eluent every 2 to 3 days (4.1.16).
4.1.16.3.3 Borate/gluconate concentrate
The following eluent concentrate has proved useful for the preparation of the eluent (4.1.16.3.4) and the pretreatment of
the samples.
-Weigh 16 g of gluconic acid, sodium salt (4.1.5), 18 g of boric acid (4.1.7), and 25 g of disodium tetraborate
(4.1.4) into a graduated flask, nominal capacity 1 000 ml, dissolve in approximately 500 ml of water (4.1),
add 250 ml of glycerol (4.1.8) and dilute to volume with water (4.1).
The solution contains 0,073 mol/l of gluconic acid, 0,291 mol/l of boric acid, 0,124 mol/l of disodium tetraborate, and
approximately 25 % of glycerol. The solution is stable for several months if stored at 4 “C to 6 “C.
4.1.16.3.4 Borate/gluconate eluent
The following eluent can, for example, be used for the determination of iodide, thiocyanate and thiosulfate.
- Place 500 ml of water (4.1) in a graduated flask of nominal capacity 1 000 ml, add 23,5 ml of the concentrate
(4.1.16.3.3), 120 ml of acetonitrile (4.1.9) and dilute to volume with water (4.1).
The solution contains 0,0017 mol/l of gluconic acid, 0,0068 mol/l of boric acid, 0,0029 mol/l of disodium tetraborate,
approximately 0,6 % of glycerol, and approximately 12 % of acetonitrile. The pH of this solution should be in the range of
8.3 to 8.7 4). Renew the eluent every 2 to 3 days (4.1.16).
4.1.17 Stock solutions
Prepare stock solutions of concentration 1 000 mg/l for each of the anions iodide, thiocyanate and thiosulfate.
- Dissolve the appropriate mass of each of the substances, prepared as stated in table 2, in a small quantity of
water in graduated flasks of nominal capacity 1 000 ml. Dilute to volume with water. The solutions are stable for
several months if stored at 4 OC to 6 OC in polyethylene bottles.
Alternatively, use commercially available stock solutions of the required concentration.
3) pH values <4,0 or >4,5 can increase retention times or cause a peak resolution R < I,3 (for criteria for R see 4.2.2).
4) pH values <8,3 or >8,7 can increase retention times or cause a peak resolution R c I,3 (for criteria for R see 4.2.2).
0 IS0 IS0 10304=3:1997(E)
Table 2 - Mass portion and pretreatment for stock solutions
Pretreatment by drying’)
Duration
Anion Salt Temperature Mass of portion
h “C
9/l
Iodide Nal 3 103 to 106 1,1812
1 103 to 106 I,6732
Thiocyanate KSCN
1 Thiosulfate ‘) 1 Na,S,O,. 5H,O 1 Do not drv I 2.2134 I
‘) Let the substance cool in a sealed desiccator after drying.
‘) Titre adjustment is necessary prior to use.
4.1.18 Mixed standard solutions
Depending upon the concentrations expected, prepare standard solutions of different anion composition and
concentration from the stock solutions (4.1.17). The risk of changes in concentration caused by interaction with the vessel
material increases with decreasing anion concentration. Store the standard solutions in polyethylene vessels.
To avoid cross-contamination, always use the same vessels for the same anions and concentrations.
4.1.18.1 Iodide, thiocyanate, thiosulfate mixed standard solution I
The mass concentration of this solution is as follows:
p (I, SCN, S,O,) = 100 mg/l
- Pipette 10 ml each of the stock standard solution, prepared as described, in 4.1.17 into a graduated flask of
nominal capacity 100 ml and dilute to volume with water (4.1).
Store the solution in a polyethylene vessel. The solution is stable for about one week if stored at 4 “C to 6 “C.
4.1.18.2 Iodide, thiocyanate, thiosulfate mixed standard solution II
The mass concentration of this solution is as follows:
p (I, SCN, S,O,) = 10 mg/l
- Pipette 10 ml of mixed anion standard solution I (4.1.18.1) into a graduated flask of nominal capacity 100 ml and
dilute to volume with water (4.1).
The solution is stable for only 1 to 2 days, even if stored at 4 “C to 6 “C.
Prepare further standard solutions by appropriate dilutions of mixed standard solution I (4.1.18.1).
4.1.19 Anion calibration solutions
Depending on the anion concentration expected, use the stock solution (4.1.17) or the mixed standard solutions (4.1.18.1
and 4.1.18.2) to prepare 5 to 10 calibration solutions covering the expected working range as evenly as possible.
For example, proceed as follows for the range I,0 mg/l to 10 mg/l for the anions iodide, thiocyanate and thiosulfate.
- Into a series of graduated flasks of nominal capacity 100 ml, pipette 1 ml, 2 ml, 3 ml, 4 ml, 5 ml, 6 ml, 7 ml, 8 ml,
9 ml and 10 ml of the mixed standard solution I (4.1.18.1), dilute to volume with water and add 0,l ml of the
sodium hydroxide solution5j6) (4.1.10).
4.1.20 Blank solution
Fill a graduated flask of nominal capacity 100 ml, up to volume with water and add 0,l ml of sodium hydroxide solution
(4.1.10)5)6).
5) Alternatively, use the eluent concentrate according to 4.1 .I 6.2.1 or 4.1.16.3.3.
6) The addition of 0,l ml of sodium hydroxide solution or 0,l ml of eluent concentrate will reduce the concentration of the reference
solution. This effect is compensated for by the equal treatment of the sample.
IS0 10304-3: 1997(E)
4.2 Apparatus
Usual laboratory apparatus and
4.2.1 Ion chromatography system, complying with the quality requirements of 4.2.2. In general it shall consist of the
following components (see figure I):
4.2.1 .l Ion chromatography apparatus, comprising
-
eluent reservoir;
- pump, suitable for HPLC;
- sample injection system incorporating a sample loop (e.g. sample loop of volume 50 ul);
- precolumn (see 4.5.2) containing e.g. the same resin material as the analytical separator column or packed with
a macroporous polymer;
- separator column with the specified separating performance (4.2.2);
- conductivity detector (with or without a suppressor device assembly) or UV detector (e.g. spectrophotometer;
190 nm to 400 nm) or amperometric detector;
- Recording device (e.g. recorder, integrated with printer).
r
Sample injection
system
I
,
Separator
Eluent Pump p Precolumn e Detector - Waste
column
Registration and
evaluation
r-l
Figure 1 - Schematic representation of an ion chromatography system
4.2.2 Quality requirements for the separator column
The separator column is the essential part of the ion chromatographic system. Its separation performance depends on
several operating factors, such as column material and type of eluent. Within the scope of this standard, use only those
separator columns that yield a baseline-resolved separation of all the components of the injected ions (e.g. iodide,
thiocyanate and thiosulfate; see figure 2) at a concentration level of 1 mg/l each. If only some of the anions shown in
figure 2 have to be determined, this requirement is applicable to those anions. For chromatograms of samples and
standard solutions of higher concentrations, the resolution to the nearest (interfering) peak (see figure 3) shall not fall
below R = I,3 [see equation (I)].
0 IS0 IS0 10304=3:1997(E)
SCN-
I I I I
Time, min
NOTE: Elution sequence and retention times can vary, depending on the type of column and composition of the eluent.
Figure 2 - Example of a chromatogram of a column conforming to this part of IS0 10304
I
fR2
-
Time, s
Graphical representation of the parameters to calculate the peak resolution R
Figure 3 -
IS0 10304-3: 1997(E) 0 IS0
Calculate the peak resolution R using equation (1):
2 (tR2 - tR])
. . .
(1)
R2,I =
fw2 + w/)
is the resolution for the peak pair 2,l;
R2 1
t ‘ is the retention time, in seconds, of peak 1;
Rl
t is the retention time, in seconds, of peak 2;
R2
is the peak width, in seconds, on the time axis of peak 1;
?
1 is the peak width, in seconds, on the time axis of peak 2.
w2
4.2.3 Additional equipment, including the following:
- drying oven;
- desiccator;
- graduated flasks, of nominal capacities 100 ml, 1 000 ml and 5 000 ml;
- graduated flasks, of nominal capacity 100 ml and made of plastics, to be used for low concentrations
(e.g. L 0,l mg/l);
- graduated pipettes, of nominal capacity 1 ml to 10 ml or microlitre syringes;
-
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