SIST EN ISO 23631:2006
(Main)Water quality - Determination of dalapon, trichloroacetic acid and selected haloacetic acids - Method using gas chromatography (GC-ECD and/or GC-MS detection) after liquid-liquid extraction and derivatization (ISO 23631:2006)
Water quality - Determination of dalapon, trichloroacetic acid and selected haloacetic acids - Method using gas chromatography (GC-ECD and/or GC-MS detection) after liquid-liquid extraction and derivatization (ISO 23631:2006)
This International Standard specifies a method for the determination of dalapon, trichloroacetic acid (TCA) and selected haloacetic acids (see Table 1) in ground water and drinking water by gas chromatography (GC-ECD and/or GC-MS detection) after liquid-liquid-extraction and derivatization using diazomethane. Depending on the matrix, the method is applicable to a concentration range from 0,5 µg/l to 10 µg/l. The validated reporting limit of TCA and dalapon is about 0,05 µg/l (see Table C.1). Detection by electron-capture detector (ECD) in general leads to lower detection limits. Detection by mass spectrometry (MS) allows analyte identification.
Wasserbeschaffenheit - Bestimmung von Dalapon, Trichloressigsäure und ausgewählten Halogenessigsäuren - Verfahren mittels Gaschromatographie (GC-ECD und/oder GC-MS-Detektion) nach Flüssig-Flüssig-Extraktion und Derivatisierung (ISO 23631:2006)
Diese Internationale Norm legt ein Verfahren zur Bestimmung von Dalapon, Trichloressigsäure (TCA) und ausgewählten Halogenessigsäuren (siehe Tabelle 1) mittels Gaschromatographie (GC-ECD und/oder GC-MS-Detektion) in Grund- und Trinkwasser nach Flüssig-Flüssig-Extraktion und Derivatisierung mit Diazomethan fest. In Abhängigkeit von der Matrix kann für das Verfahren von einem Arbeitsbereich zwischen 0,5 µg/l und 10 µg/l ausgegangen werden. Für TCA und Dalapon können niedrigere Konzentrationen bis herab zu 0,05 µg/l bestimmt werden (siehe Tabelle C.1). Die Detektion mittels Elektroneneinfangdetektor (ECD) ermöglicht im Allgemeinen niedrigere Bestimmungsgrenzen; die Detektion mittels Massenspektrometrie (MS) führt zu einer spezifischen Identifizierung.
Die Anwendbarkeit des Verfahrens auf weitere, in Tabelle 1 nicht genannte Verbindungen oder andere Wässer ist nicht ausgeschlossen; sie muss jedoch im Einzelfall geprüft werden.
Qualité de l'eau - Dosage du dalapon, de l'acide trichloroacétique et d'acides haloacétiques selectionnés - Méthode par chromatographie en phase gazeuse (détection CG-DCE et/ou CG-SM) apres extraction liquide-liquide et dérivatisation (ISO 23631:2006)
L'ISO 23631:2006 spécifie une méthode de dosage du dalapon, de l'acide trichloroacétique (ATC) et d'acides haloacétiques sélectionnés présents dans les nappes phréatiques et dans l'eau potable par chromatographie en phase gazeuse (détection CG-DCE et/ou CG-SM) après extraction liquide-liquide et dérivatisation à l'aide de diazométhane. En fonction de la matrice, la méthode est applicable dans la plage de concentrations allant de 0,5 microgrammes par litre à 10 microgrammes par litre. Le seuil de quantification validé de l'acide trichloroacétique (ATC) et du dalapon est d'environ 0,05 microgrammes par litre. La détection par un détecteur à capture d'électrons (DCE) conduit généralement à des seuils de détection plus bas. La détection par spectrométrie de masse (SM) permet l'identification d'un analyte.
Kakovost vode - Določevanje 2,2-dikloropropionske kisline (dalapon), trikloroocetne kisline in izbranih halogenoocetnih kislin – Metoda plinske kromatografije z ECD detektorjem in/ali z masno selektivnim detektorjem (GCD-ECD in/ali GC-MS detekcija) po tekočinsko-tekočinski ekstrakciji in derivatizaciji (ISO 23631:2006)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 23631:2006
01-julij-2006
.DNRYRVWYRGH'RORþHYDQMHGLNORURSURSLRQVNHNLVOLQH GDODSRQ
WULNORURRFHWQHNLVOLQHLQL]EUDQLKKDORJHQRRFHWQLKNLVOLQ±0HWRGDSOLQVNH
NURPDWRJUDILMH](&'GHWHNWRUMHPLQDOL]PDVQRVHOHNWLYQLPGHWHNWRUMHP *&'
(&'LQDOL*&06GHWHNFLMD SRWHNRþLQVNRWHNRþLQVNLHNVWUDNFLMLLQGHULYDWL]DFLML
,62
Water quality - Determination of dalapon, trichloroacetic acid and selected haloacetic
acids - Method using gas chromatography (GC-ECD and/or GC-MS detection) after
liquid-liquid extraction and derivatization (ISO 23631:2006)
Wasserbeschaffenheit - Bestimmung von Dalapon, Trichloressigsäure und ausgewählten
Halogenessigsäuren - Verfahren mittels Gaschromatographie (GC-ECD und/oder GC-
MS-Detektion) nach Flüssig-Flüssig-Extraktion und Derivatisierung (ISO 23631:2006)
Qualité de l'eau - Dosage du dalapon, de l'acide trichloroacétique et d'acides
haloacétiques selectionnés - Méthode par chromatographie en phase gazeuse (détection
CG-DCE et/ou CG-SM) apres extraction liquide-liquide et dérivatisation (ISO
23631:2006)
Ta slovenski standard je istoveten z: EN ISO 23631:2006
ICS:
13.060.50
SIST EN ISO 23631:2006 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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EUROPEAN STANDARD
EN ISO 23631
NORME EUROPÉENNE
EUROPÄISCHE NORM
February 2006
ICS 13.060.50
English Version
Water quality - Determination of dalapon, trichloroacetic acid
and selected haloacetic acids - Method using gas
chromatography (GC-ECD and/or GC-MS detection) after liquid-
liquid extraction and derivatization (ISO 23631:2006)
Qualité de l'eau - Dosage du dalapon, de l'acide Wasserbeschaffenheit - Bestimmung von Dalapon,
trichloroacétique et d'acides haloacétiques selectionnés - Trichloressigsäure und ausgewählten Halogenessigsäuren
Méthode par chromatographie en phase gazeuse - Verfahren mittels Gaschromatographie (GC-ECD
(détection CG-DCE et/ou CG-SM) après extraction liquide- und/oder GC-MS-Detektion) nach Flüssig-Flüssig-
liquide et dérivatisation (ISO 23631:2006) Extraktion und Derivatisierung (ISO 23631:2006)
This European Standard was approved by CEN on 16 January 2006.
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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania,
Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: rue de Stassart, 36 B-1050 Brussels
© 2006 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 23631:2006: E
worldwide for CEN national Members.
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EN ISO 23631:2006 (E)
Foreword
This document (EN ISO 23631:2006) 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 August 2006, and conflicting national
standards shall be withdrawn at the latest by August 2006.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium,
Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary,
Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
Endorsement notice
The text of ISO 23631:2006 has been approved by CEN as EN ISO 23631:2006 without any
modifications.
2
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INTERNATIONAL ISO
STANDARD 23631
First edition
2006-02-01
Water quality — Determination of
dalapon, trichloroacetic acid and selected
haloacetic acids — Method using gas
chromatography (GC-ECD and/or GC-MS
detection) after liquid-liquid extraction
and derivatization
Qualité de l'eau — Dosage du dalapon, de l'acide trichloroacétique et
d'acides haloacétiques sélectionnés — Méthode par chromatographie
en phase gazeuse (détection CG-DCE et/ou CG-SM) après extraction
liquide-liquide et dérivatisation
Reference number
ISO 23631:2006(E)
©
ISO 2006
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ISO 23631:2006(E)
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ii © ISO 2006 – All rights reserved
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ISO 23631:2006(E)
Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Normative references . 2
3 Principle. 2
4 Interferences . 2
5 Reagents. 2
6 Apparatus . 5
7 Sampling and sample pre-treatment. 7
8 Procedure . 7
9 Calibration . 10
10 Calculation. 13
11 Expression of results . 14
12 Test report . 15
Annex A (informative) Examples of gas chromatograms . 16
Annex B (informative) Mass spectra of methylated dalapon and haloacetic acids. 19
Annex C (informative) Precision data. 23
Bibliography . 24
© ISO 2006 – All rights reserved iii
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ISO 23631:2006(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 23631 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods.
iv © ISO 2006 – All rights reserved
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ISO 23631:2006(E)
Introduction
The user should be aware the particular problems could require the specifications of additional marginal
conditions.
© ISO 2006 – All rights reserved v
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INTERNATIONAL STANDARD ISO 23631:2006(E)
Water quality — Determination of dalapon, trichloroacetic acid
and selected haloacetic acids — Method using gas
chromatography (GC-ECD and/or GC-MS detection) after liquid-
liquid extraction and derivatization
WARNING — Persons using this International Standard should be familiar with 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.
Diazomethane is explosive, extremely toxic and severely irritating, causing pulmonary oedema when
inhaled in high concentrations. Long-term, low-level exposure may lead to sensitization, resulting in
asthma-like symptoms. Also, diazomethane and several of its chemical precursors have been cited as
carcinogens.
IMPORTANT — It is absolutely essential that tests conducted according to this International Standard
be carried out by suitably trained staff.
1 Scope
This International Standard specifies a method for the determination of dalapon, trichloroacetic acid (TCA) and
selected haloacetic acids (see Table 1) in ground water and drinking water by gas chromatography (GC-ECD
and/or GC-MS detection) after liquid-liquid-extraction and derivatization using diazomethane. Depending on
the matrix, the method is applicable to a concentration range from 0,5 µg/l to 10 µg/l. The validated reporting
limit of TCA and dalapon is about 0,05 µg/l (see Table C.1). Detection by electron-capture detector (ECD) in
general leads to lower detection limits. Detection by mass spectrometry (MS) allows analyte identification.
This method may be applicable as well to compounds not mentioned in Table 1 or to other types of water.
However, it is necessary to verify the applicability of this method for these special cases.
Table 1 — Haloacetic acids determined by this method
Name Molecular formula Relative molecular mass CAS registry No.
Bromochloroacetic acid C H BrClO 173,4 5589-96-8
2 2 2
a
Dalapon C H Cl O 143,0 75-99-0
3 4 2 2
Dibromoacetic acid C H Br O 217,8 631-64-1
2 2 2 2
Dichloroacetic acid C H Cl O 128,9 79-43-6
2 2 2 2
Monobromoacetic acid C H BrO 138,9 79-08-3
2 3 2
Monochloroacetic acid C H ClO 94,5 79-11-8
2 3 2
Trichloroacetic acid (TCA) C HCl O 163,4 76-03-9
2 3 2
a
2,2-Dichloropropionic acid.
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ISO 23631:2006(E)
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 3696:1987, Water for analytical laboratory use — Specification and test methods
ISO 5667-1, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes
ISO 5667-2, Water quality — Sampling — Part 2: Guidance on sampling techniques
ISO 5667-3, Water quality — Sampling — Part 3: Guidance on the preservation and handling of water
samples
3 Principle
Dalapon, trichloroacetic acid (TCA) and selected haloacetic acids are extracted from the acidified water
sample with methyl-tert-butyl ether (MTBE). The extract is concentrated by evaporation.
The analytes are methylated using diazomethane.
The methylated analytes are separated, identified and quantified by means of capillary gas chromatography
with electron-capture detection (GC-ECD) and/or mass spectrometry (GC-MS).
4 Interferences
4.1 Interferences with the extraction procedure
Suspended particles in the water may interfere with the liquid-liquid-extraction procedure causing problems in
layer separation. In this case, filter the water sample through a glass fibre filter (6.15) prior to enrichment.
4.2 Interferences with the gas chromatography and mass spectrometry procedure
Interferences may be caused e.g. by the injection system used or by inadequate separation of the analytes.
Experienced operators, using the information given in the instrument manuals, may be able to minimize this
type of interference. Regular checking of the chromatographic and spectrometric system is required to
maintain adequate performance. Required system stability should be checked regularly by the use of a
GC-standard.
Insufficiently purified solvents (5.6) as well as insufficiently purified sodium chloride (5.10) may cause severe
interferences. Reagents used in the method to perform derivatization may lead to interferences in the
ECD-chromatograms. Therefore, it is highly recommended that temperatures of the diazomethane building
process be carefully kept in limits (see 5.19).
5 Reagents
Use solvents and reagents of sufficient purity, i.e. with negligibly low impurities compared with the
concentration of analytes to be determined. As reagents use, as far as available, “residual grade” or better in
order to obtain clean blanks. Check blanks regularly and establish proper charge control.
5.1 Water, complying to grade 1 as defined in ISO 3696:1987, or equivalent.
2 © ISO 2006 – All rights reserved
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ISO 23631:2006(E)
5.2 Operating gases for the gas chromatography/mass spectrometry, of high purity and in accordance
with manufacturer's specifications.
5.3 Nitrogen, of high purity, i.e. minimum 99,996 % by volume, for concentration by evaporation.
5.4 Diethyl ether, C H O.
4 10
NOTE Stabilizers may cause interferences.
5.5 Ethanol, C H OH.
2 5
5.6 Solvents, e.g. ethyl acetate, C H O ; acetone, C H O.
4 8 2 3 6
5.7 Methyl-tert-butyl ether (MTBE), C H O.
5 12
5.8 Benzoic acid, dissolved in ethanol, c(C H O ) = 0,2 mol/l.
7 6 2
5.9 N-methyl-N-nitroso-4-toluenesulfonamide, C H N O S.
8 10 2 3
5.10 Sodium chloride, NaCl (e.g. heated at 550 °C for 4 h).
5.11 Potassium hydroxide solution, w(KOH) = 60 %.
5.12 Sodium hydroxide solution, c(NaOH) = 0,1 mol/l.
5.13 Sodium thiosulfate pentahydrate, Na S O ·5 H O.
2 2 3 2
5.14 Phenolphthalein, C H O .
20 14 4
5.15 Acetic acid, w(CH COOH) = 10 %.
3
5.16 Mineral acid, e.g. hydrochloric acid, w(HCl) = 25 %.
5.17 Methylated reference substances.
Methylated reference substances (methyl esters of the acids listed in Table 1) of defined concentration
suitable for the preparation of reference solutions for gas chromatography (9.2).
5.17.1 Stock solutions of individual methylated reference substances.
As an example, pipette 50 mg of each of the methylated reference substances into 100 ml volumetric flasks,
dissolve in MTBE (5.7) and dilute to volume with MTBE.
Store stock solutions at about −18 °C, protected from light. They are stable for about 1 year.
5.17.2 Multiple-substance stock solutions of methylated reference substances.
As an example, transfer 2 ml of each of the solution of the individual substance (5.17.1) into a 100 ml
volumetric flask and dilute to volume with MTBE (5.7).
Store stock solutions at about −18 °C, protected from light. They are stable for about 1 year.
5.17.3 Reference solutions of methylated reference substances.
Solutions of defined concentration suitable for multipoint calibration (working solution for gas chromatography).
Prepare the reference solutions by an adequate dilution of the stock solution (5.17.2) with MTBE (5.7).
Store reference solutions at a maximum of +10 °C or below (e.g. in a refrigerator), protected from light. They
are stable for about 6 months.
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ISO 23631:2006(E)
5.18 Non-methylated reference substances.
5.18.1 General requirements.
Reference substances (acids, listed in Table 1) of defined concentration, suitable for the preparation of
reference solutions used for spiking water samples. Spike samples for calibration of the total procedure (9.3
and 9.4) and calculation of the overall recovery, i.e. total of extraction recovery and recovery of the
derivatization step (9.5).
5.18.2 Stock solutions of individual non-methylated reference substances.
As an example, place 50 mg each of a non-methylated reference substance into a 100 ml volumetric flask,
dissolve with MTBE (5.7) and dilute to volume with MTBE.
Store stock solutions at about −18 °C, protected from light. They are stable for about 1 year.
5.18.3 Multiple substance stock solutions of non-methylated reference substances.
As an example, transfer 2 ml of each of the solution of the individual substance (5.18.2) into a 100 ml
volumetric flask and dilute to volume with MTBE (5.7).
Store stock solutions at about −18 °C, protected from light. They are stable for about 1 year.
5.18.4 Reference solutions of non-methylated reference substances.
Prepare solutions of defined concentration suitable for multipoint calibration of the total procedure and spike
water samples appropriately. Prepare the reference solutions by an adequate dilution of the stock solution
(5.18.3) with MTBE (5.7).
Store reference solutions at a maximum of +10 °C or below (e.g. in a refrigerator), protected from light. They
are stable for about 6 months.
5.19 Diazomethane solution (derivatization reagent).
WARNING — N-methyl-N-nitroso-4-toluenesulfonamide is an irritant and all skin contact shall be
avoided.
Prepare diazomethane in a distillation apparatus, e.g. as shown in Figure 1. Pay attention to warning note in
the clause “warning” on page 1.
For security reasons, install two wash bottles; keep the first one empty for the purpose of protecting the
solution from backflush and fill the second with acetic acid (5.15).
Pipette 8 ml of KOH solution (5.11) and 10 ml of ethanol (5.5) in a 250 ml reaction flask.
Suspend 5,0 g of N-methyl-N-nitroso-4-toluenesulfonamide (5.9) in 45 ml of diethyl ether (5.4) or MTBE (5.7)
in a pressure-equalizing funnel.
Cautiously warm the reaction flask to about 60 °C (water bath) and, within 20 min, dropwise add the
N-methyl-N-nitroso-4-toluenesulfonamide suspension from the pressure-equalizing funnel. If MTBE is used as
a solvent, slightly increase the temperature by some degrees in order to maintain a smooth distillation process.
Collect the diazomethane being formed during this process together with the distilled diethyl ether or MTBE in
the trap (cooled with ice/NaCl).
After this reaction, add an additional 10 ml of the same ether (diethyl ether or MTBE) through the funnel and
distil the remaining diazomethane.
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ISO 23631:2006(E)
Stopper the trap and store it at about −18 °C, protected from light. Check the stability of diazomethane
solution regularly. It should always show an intensive yellow colour.
The solution is stable for at least 1 year.
Excess diazomethane and N-methyl-N-nitroso-4-toluenesulfonamide can be destroyed by adding a solution of
acetic acid (5.15). It is recommended that reaction flask and pressure-equalizing funnel be rinsed with acetic
acid. The remaining distillation apparatus may be cleaned by distilling 50 ml of ethanol (5.5).
The concentration of the diazomethane solution (derivatization reagent) can be checked by titration. If this
step is desired, proceed as follows: Insert 3 ml of 0,2 mol/l of ethanolic benzoic acid solution (5.8) in a titration
flask. Add 1 ml of etheric diazomethane solution (diethyl ether or MTBE) and phenolphthalein (5.14). Add
0,1 mol/l of sodium hydroxide solution (5.12) using a burette until the solution becomes permanently pink.
5.20 Internal standard, e.g. 2-bromopropionic acid, C H BrO or 2,3-dichloropropionic acid C H Cl O
3 5 2 3 4 2 2
(9.4).
6 Apparatus
Equipment or parts of it, which are likely to come into contact with the water sample or its extract, shall be free
from residues causing interferences. It is recommended to use vessels made of glass, stainless steel or
polytetrafluoroethene (PTFE).
6.1 Flat-bottomed flasks, preferably brown glass, 250 ml, with glass stoppers.
6.2 Graduated cylinders, 250 ml.
6.3 Volumetric flasks, 10 ml, 25 ml, 50 ml and 100 ml.
6.4 Volumetric pipettes, different sizes between 1 ml and 50 ml.
6.5 Evaporation assembly, for sample enrichment and extract concentration.
6.6 Vials, suitable for automatic or manual injection. Glass vials with inert stopper, such as PTFE-coated
septum, for storage of extracts.
6.7 Magnetic stirrer, including PTFE-coated stirrer bar of suitable size.
6.8 Microseparator, device for phase separation.
6.9 Separating funnel, 250 ml and 500 ml.
6.10 Apparatus for preparing diazomethane, (see example in Figure 1), comprising the following:
6.10.1 Round-bottomed flask, double-necked, 250 ml.
6.10.2 Pressure-equalizing funnel, 100 ml.
6.10.3 Distillation column, for example, Vigreux column.
6.10.4 Distillation head.
6.10.5 Condenser, for example, Liebig condenser.
6.10.6 Round bottomed flask, 100 ml.
6.10.7 Flask for absorption of diazomethane, 250 ml.
6.10.8 Security flask, 250 ml, or a commercial distillation apparatus.
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ISO 23631:2006(E)
Key
1 acetic acid (w = 10 %) for absorption of diazomethane
Figure 1 — Example of a distillation apparatus for preparing diazomethane
6.11 Capillary gas chromatograph with electron-capture detector (ECD), equipped with a
non-discriminating injection system (6.13), gas supply in accordance with the respective manufacturer's
instructions.
Proper identification of the methylated dalapon and haloacetic acids according to Table 1 requires analysis on
a minimum of two capillary columns of significantly differing polarity for both sample solution and standard
solution. It is advantageous to connect both columns to one injector for simultaneous sample application.
However, with this technique, misinterpretation caused by peak overlapping cannot completely be ruled out. In
this event, two quantitative results will be obtained, with the lower value probably being more accurate.
6.12 Capillary gas chromatograph with mass spectrometric detector (MS), equipped with a
non-discriminating injection system (6.13), electron impact ionization, gas supply in accordance with the
respective manufacturer's instructions.
6.13 Non-discriminating GC-Injector, e.g. split/splitless injection system, programmable temperature
vaporizer (PTV) or on-column-injection system.
6.14 Capillary columns, for gas chromatography (for examples of gas chromatograms, see Annex A). It is
advantageous to use columns of a length W 50 m.
6.15 Borosilicate glass fibre filter, diameter of fibres 0,75 µm to 1,5 µm, with inorganic binding material.
6.16 pH meter with electrodes.
6.17 Injection syringes, nominal capacity 5 µl or 10 µl.
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ISO 23631:2006(E)
7 Sampling and sample pre-treatment
Collect samples as specified in ISO 5667-1, ISO 5667-2 and ISO 5667-3.
For sampling, use thoroughly cleaned, preferably brown, flat-bottomed glass flasks (6.1), usually 250 ml.
Rinse flasks and stoppers with the water to be sampled.
Fill the bottles completely with the water to be examined. Dechlorinate water samples containing chlorine by
immediately adding approximately 25 mg of sodium thiosulfate pentahydrate (5.13).
If storage is unavoidable, store the sample at 4 °C in the dark. Treat and analyse the samples as soon as
possible after sample collection (within 3 days).
8 Procedure
8.1 Sample preparation and extraction
8.1.1 Sample preparation
For the extraction, measure 200 ml ± 10 ml of the water sample under investigation in a graduated cylinder
(6.2) or calculate the exact volume of the water sample after weighing.
Add the internal standard (5.20), if calibration with an internal standard covering the total procedure is to be
performed.
Adjust with mineral acid (5.16) to a pH of (1,0 ± 0,2).
Add about 20 g of sodium chloride (5.10) to the water sample.
Extract the water sample according to 8.1.2 or 8.1.3.
8.1.2 Extraction by stirring with a magnetic stirrer and a microseparator
Place a magnetic stirring rod in the sample container (e.g. 250 ml flat-bottomed flask; 6.1) and add 20 ml of
−1
MTBE (5.7), stir the water sample using a magnetic stirrer (6.7) at about 1 000 min for 5 min to 10 min, and
then allow to stand for about 5 min.
Separate the organic phase in the microseparator as follows: Place the microseparator (6.8) on the sample
container and pour water (5.1) into the funnel until the liquid level of the organic phase has risen high enough
to allow the sample extract to be removed with a pipette for further procedure.
8.1.3 Extraction by shaking in the separating funnel
Shake the water sample twice in the separating funnel (6.9) with 20 ml of MTBE (5.7) for 20 min each time.
Separate and collect the organic phase after each extraction step. After completion of the extraction, combine
the organic phases.
8.2 Concentration and derivatization
Concentrate the extract (8.1.2 or 8.1.3) carefully to a final volume of about 0,8 ml to 0,9 ml (e.g. in a nitrogen
stream or on a rotary evaporator under reduced pressure, 400 hPa, 30 °C). There is no extract-drying step
necessary as long as MTBE is used for extraction purposes.
Add a sufficient volume (about 100 µl to 200 µl) of diazomethane solution (5.19) until a persistent yellow
colouration appears.
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ISO 23631:2006(E)
Stopper the flask and keep in the dark for about 15 min.
At the end of the reaction time, concentrate the solution with nitrogen to a volume of not less than 0,8 ml in
order to remove excess diazomethane.
If a calibration is being performed with an external standard (9.3), bring to volume (exactly 1 ml) with MTBE
(5.7).
8.3 Gas chromatography analysis of individual compounds
8.3.1 Procedure with electron capture detector (GC-ECD)
Individual compounds in the sample are detected by means of an electron capture detector (ECD), by
comparing the retention times (RT) correspondi
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