ISO 11423-1:1997
(Main)Water quality — Determination of benzene and some derivatives — Part 1: Head-space gas chromatographic method
Water quality — Determination of benzene and some derivatives — Part 1: Head-space gas chromatographic method
Qualité de l'eau — Détermination du benzène et de certains dérivés benzéniques — Partie 1: Méthode par chromatographie en phase gazeuse de l'espace de tête
La méthode décrite est applicable à la détermination du benzène, du méthylbenzène (toluène), des diméthylbenzènes (xylènes) et de l'éthylbenzène (dans la suite l'abréviation BTX est utilisée) dans des échantillons homogènes d'eau et d'eau résiduaire à des concentrations supérieures à 2 µg/l. Dans des échantillons organiquement pollués, la limite de détermination peut, suivant la matrice de l'échantillon, être supérieure. Des concentrations élevées peuvent être déterminées en diluant l'échantillon. D'autres dérivés et composés apolaires présentant des propriétés physiques similaires peuvent également être déterminés par cette méthode. Il convient alors de vérifier l'applicabilité de la méthode à l'échantillon d'eau donné.
Kakovost vode - Določevanje benzena in nekaterih derivatov - 1. del: Plinska kromatografska metoda s tehniko “head-space”
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-januar-1998
.DNRYRVWYRGH'RORþHYDQMHEHQ]HQDLQQHNDWHULKGHULYDWRYGHO 3OLQVND
NURPDWRJUDIVNDPHWRGDVWHKQLNR³KHDGVSDFH´
Water quality -- Determination of benzene and some derivatives -- Part 1: Head-space
gas chromatographic method
Qualité de l'eau -- Détermination du benzène et de certains dérivés benzéniques --
Partie 1: Méthode par chromatographie en phase gazeuse de l'espace de tête
Ta slovenski standard je istoveten z: ISO 11423-1:1997
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
First edition
1997-06-I 5
Water quality - Determination of benzene
and some derivatives -
Part 1:
Head-space gas chromatographic method
&alit& de I’eau - DBtermination du benzene et de certains d&iv&
benzhniques -
Partie I: Mhthode par chromatographie en phase gazeuse de I’espace de
t6te
Reference number
IS0 11423-l : 1997(E)
IS0 11423-l : 1997(E)
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 11423-I was prepared by Technical Committee ISOTTC 147, Water qua/ity,
Subcommittee SC 2, Physical, chemical, biochemical methods.
IS0 11423 consists of the following parts, under the general title Water quality - Determination of benzene and
some derivatives:
- Part I: Head-space gas chromatographic method
- Part 2: Method using extraction and gas chromatography
Annexes A, B, C and D of this part of IS0 11423 are for information only.
0 IS0 1997
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 the publisher.
International Organization for Standardization
Case postale 56 l CH-1211 Geneve 20 l Switzerland
Internet central @ iso.ch
c=ch; a=400net; p=iso; o=isocs; s=central
x.400
Printed in Switzerland
ii
IS0 11423=1:1997(E)
Introduction
This part of IS0 11423 describes a head-space method of sample treatment for the gas chromatographic
determination of benzene and some of its derivatives in water.
For an extraction procedure followed by gas chromatography, see IS0 11423-2.
given
Which of these methods is applicable in a case depends for instance on the type of samp le to be analysed
and the instruments available to the analyst . The method used is the n described in the test report.
This page intentionally left blank
I§0 11423-l :1997(E)
INTERNATIONAL STANDARD 0 IS0
Water quality - Determination of benzene and some derivatives -
Part 1:
Head-space gas chromatographic method
1 Scope
The method described is applicable to the determination of benzene, methylbenzene (toluene), dimethylbenzenes
(xylenes) and ethylbenzene (abbreviated hereafter to BTX) in homogeneous samples of water and waste water in
concentrations above 2 pg/l. In samples that are organically polluted, the limit of determination may, depending on
the matrix of the sample, be higher. High concentrations may be determined by diluting the sample.
A number of further derivatives and nonpolar compounds with similar physical properties may also be determined
by this method. The applicability of the method should be verified for the particular water sample.
2 Principle
A defined volume of unfiltered water sample is heated in a gas-tight septum-covered vial. After establishment of
equilibrium between the gaseous and liquid phases, an aliquot of the gaseous phase is transferred to a gas
chromatograph. Separation of benzene and its derivatives is carried out by injection on two capillary columns with
stationary phases of different polarity (e.g. by simultaneous splitting) and determination using a suitable detector (for
identification of compounds see 7.3).
3 Interferences
Loss of BTX may occur during sampling, transport storage and preparation of samples due to evaporation and
stripping. Volatile organic compounds in the ambient air may contaminate water samples and water used for blank
tests, leading to high limits of detection and high blank values, respectively.
To avoid errors due to sorption or desorption of constituents, samples should not come into contact with plastics
materials.
Compared with the extraction procedure in IS0 11423-2, interferences due to suspended matter or emulsifiers are
less frequent with head-space analysis. Solvents can modify the normal equilibrium with the gaseous phase. The
presence of a second liquid phase prohibits the use of the head-space method.
Specific problems in the gas chromatographic system shall be handled according to the manufacturer’s instruction.
@ IS0
IS0 11423-l :1997(E)
The determination may be hindered by superposition of other hydrocarbons, for instance mineral oil constituents,
which may also result in column overload.
If the results from the two different columns differ significantly, repeat the analysis with another separating phase or
a specific detector.
4 Apparatus
Keep all precleaned bottles and vials in an upside-down position for 1 h at 150 OC in a ventilated drying oven before
use. After this procedure, protect them from pollution, for instance by covering them with aluminium foil while they
cool and closing them as soon as they are cool.
4.1 Conical-shoulder bottles, nominal capacity e.g. 250 ml, of non-actinic glass with tight stopper or PTFE- or
aluminium-lined cap.
4.2 Magnetic stirrer with PTFE-coated bars.
43 . Heating device (e.g. water bath).
4.4 Pipettes, capacity e.g. 1 ml, 2 ml, 5 ml, 10 ml, 25 ml and 50 ml, made of glass.
Gas washing-bottle attachment with ground glass cone and sintered disc.
4.5
4.6 Graduated flasks, capacity 100 ml, 250 ml and 1 000 ml.
sampling vials with PTFE or aluminium-coated
47 Crimp-top septum and filler cap, suited to the automatic
head -space dosi ng system used.
4.8 Automatic head-space dosing system with thermostatting facility or heatable gas-tight injection syringe,
nominal capacity 2,5 ml or 5 ml.
The correct choice of the syringe is essential to minimize the injection error.
Crimp-top vials with PTFE septum and filler cap, capacity 10 ml, for the stock solutions.
4.9
with glass insert a ssem bly and flame ionization detector (FID),
4.10 Gas chromatograph supplied with gases as
specified by the manufacture r.
Capillary columns for gas chromatography (see annex B).
4.11
with BTX are
NOTE - If alkanes with retention times identical expected, the Kovacs
indices are useful for the choice of the
columns used.
4.12 Injection syringes, capacity 50 ~1 and 100 ul.
5 Reagents
Use only reagents of recognized analytical grade and only water complying with 5.1.
IS0 11423-l : 1997(E)
@ IS0
5.1 Water for dilutions and the reagent blank.
The BTX content of the water shall be as low as possible. In case of contamination, the water may be treated as
follows:
Fill the water into conical-shoulder bottles (4.1), place a gas washing-bottle attachment (4.5) near the bottom of the
bottle, heat the water to approximately 60 OC. Pass a stream of nitrogen (approximately 180 ml/min) through the
water for 1 h, then allow the water to cool to room temperature while still passing nitrogen through it. Close the
bottle tightly and store in the dark.
If necessary, pass nitrogen through the water immediately before use.
Check the quality of the water before and after treatment. If contamination is still detected, use another gas for
purification, or purify the gas used.
5.2 Operating gases for the gas chromatographic system (nitrogen, helium, hydrogen, synthetic air) according to
the manufacturer’s instruction.
5.3 Calibration standard substances, each of highest purity.
Benzene
G6H6
Methylbenzene (toluene)
C7H8
1,2-Dimethylbenzene (o-xylene)
C8H10
1,3-Dimethylbenzene (m-xylene)
C8H10
1,4-Dimethylbenzene (p-xylene)
C8H10
Ethylbenzene
C8H10
5.4 Dimethylformamide, HCON(CH&, as solution aid. Alternatively, propan-2-one (acetone), CHsCOCHs, or
methanol, CHsOH, may be used.
Determine their reagent blanks as described in 7.3.
5.5 Potassium carbonate, K2C03, anhydrous, kept for 2 to 3 days at 200 OC to remove adsorbed volatile organic
substances, or other salt.
6 Sampling and sample preparation
If this is not possible, collect the
Head-space analysis vials (4.7) may directly be used as sampling containers.
samples in non-actinic glass conical-shoulder bottles (4.1). Use separate sets of containers for samples of waters
with different levels of BTX content.
If necessary, e.g. to achieve a lower limit of detection or to alleviate matrix effects in polluted waters, add potassium
carbonate (5.5) or another salt. Choose the quantity of potassium carbonate so that there is enough left at the
chosen temperature to leave some undissolved residue. The ionic strength of this solution shifts the equilibrium
distribution of BTX further towards the gas phase. To obtain constant conditions for head-space analysis, the
quantities of salt added and the volumes of samples and blanks must be identical.
Potassium carbonate may be added during the sampling procedure, if head-space vials (4.7) are used directly.
Place about 7 g to 8 g potassium carbonate per 5 ml of water sample into the vial and fill with the sample to the
volume needed for analysis.
It may be preferable to take larger sample volumes, which are then divided and treated with potassium carbonate in
the laboratory. The exact procedure shall be described in the test report.
@ IS0
IS0 11423-l :1997(E)
When analysing gaseous waters, it is necessary to neutralize free carbon dioxide by addition of potassium
carbonate to the head-space vials before performing the test. As the quantity added depends on the carbon dioxide
content, the addition shall be done in such a way that the carbonate ion content in the vial is about 1 % mass
fraction. If this procedure is used, the calibration shall also include this step.
If using conical-shoulder bottles (4.1), rinse them with the water to be sampled. Immerse the bottle horizontally into
a surface water so that the bottle is filled without turbulence. If sampling from a tap, slowly fill the bottle to
overflowing without turbulence.
Automatic samplers are only suitable if they are composed of glass and metals only, with as little possible plastics
materials, and if they are not used under reduced pressure. Cool the sampling container to about 4 OC and use
glass tube immersed in the sample container to convey the sample subquantities, to avoid losses.
Avoid taking composite samples, as there are always losses when mixing samples. It is possible to use the
extraction procedure described in IS0 11423-2 and mix extracts, if only an average value is needed.
Parallel to taking the sample, take an air blank consisting of a head-space vial (4.7) filled with the air present at the
sampling site, and a reagent blank using water (5.1).
If possible, start the analysis within 2 days after collection of the sample. If the sample has to be stored longer than
2 days, keep it in the conical-shoulder bottles. Store all samples at 4 OC in the dark.
Place an aliquot of the sample into a head-space vial (4.7) immediately after arrival of the samples in the laboratory,
using dispensers or other equipment that does not require reduced pressure. Close the vial with the septum and the
crimp cap and shake it, if appropriate, to partly dissolve the potassium carbonate.
Check the tightness of the crimp cap; if it can be turned, it can leak when heated.
7 Procedure
7.1 General
At the start of the procedure the laboratory shall establish whether the conditions chosen ensure a static equilibrium.
A temperature of at least 60 OC for at least 1 h has been found sufficient. The minimum time and the temperature
shall be the same for samples and blank. If the procedure is changed, repeat the check on the establishment of the
equilibrium.
atic -dosing system (4.8) follow the manufacturer’s instructions
If using an autom sample for optimization. Take care
to avoid co ntamin atio n of the system through samples.
After static equilibrium ha .S been reach ed, inject an aliqu ot of the head space into the
chromatograph, with
gas
calibration, handling blank a nd air blank samples arra .nged at the beginning and at the end of a sampling series
If using manual sample-dosing, take an aliquot of the head space using the syringe (4.12) - heated to about 20 OC
above the chosen temperature - to inject into the gas chromatograph. An injection volume of not more than 1 ~1 is
recommended.
7.2 Gas chromatography
Adjust the gas chromatograph according to the manufacturer’s instructions.
To ensure identification of the respective compounds, use at least two capillary columns with stationary phases of
different polarity. It is advantageous to have both caphy columns mounted on one injector for simultaneous
sample injection.
@ IS0 IS0 11423-l : 1997(E)
Glass or silica columns, coated with silicone or methyl silicone separating phases cross-linked (chemically bonded)
with variable phenyl content may be used (see annex B).
F
...
Questions, Comments and Discussion
Ask us and Technical Secretary will try to provide an answer. You can facilitate discussion about the standard in here.