SIST EN ISO 17495:2003
(Main)Water quality - Determination of selected nitrophenols - Method by solid-phase extraction and gas chromatography with mass spectrometric detection (ISO 17495:2001)
Water quality - Determination of selected nitrophenols - Method by solid-phase extraction and gas chromatography with mass spectrometric detection (ISO 17495:2001)
This standard specifies a method for the determination of selected nitrophenols in drinking, grund and surface water in mass concentrations > 0,5 µg/l. The method includes extraction, derivatization and gas chromatography. Exact figures on the application ranges are given in the table listing the results from the interlaboratory trial. The method includes the determination of mononitrophenols, methylnitrophenols, and selected chloronitrophenols and methylaged chloronitrophenols.
Wasserbeschaffenheit - Bestimmung ausgewählter Nitrophenole - Verfahren mittels Festphasenanreicherung und Gaschromatographie mit massenspektrometrischer Detektion (ISO 17495:2001)
Diese Internationale Norm legt ein Verfahren zur Bestimmung ausgewählter Nitrophenole (siehe Tabelle 1) in Trink-, Grund- und Oberflächenwasser in Massenkonzentrationen > 0,5 µg/l ) fest.
Tabelle 1 - Nach diesem Verfahren bestimmbare Phenole
CAS-Nr CAS-Nr
2-Nitrophenol 88-75-5 2,4-Dinitrophenol 51-28-5
3-Nitrophenol 554-84-7 2,5-Dinitrophenol 329-71-5
4-Nitrophenol 100-02-7 2,6-Dinitrophenol 573-56-8
4-Methyl-2-nitrophenol 119-33-5 2,4-Dinitro-6-methylphenol 534-52-1
3-Methyl-4-nitrophenol 2581-34-2 2,6-dimethyl-4-nitrophenol 2423-71-4
5-Methyl-2-nitrophenol 700-38-9 2,4-Dichlor-6-nitrophenol 609-89-2
3-Methyl-2-nitrophenol 4920-77-8 2,6-Dichlor-4-nitrophenol 618-80-4
CAS = Chemical Abstracts System
Qualité de l'eau - Dosage des nitrophénols sélectionnés - Méthode par extraction en phase solide avec détection par chromatographie en phase gazeuse et spectrométrie de masse (ISO 17495:2001)
La présente Norme internationale spécifie une méthode pour le dosage des nitrophénols sélectionnés (voir
Tableau 1) dans les eaux potables, les eaux souterraines et les eaux de surface, à des concentrations en masse
_ 0,5 _g/l1).
Tableau 1 — Phénols pouvant être dosés selon la présente méthode
CAS no
CAS no
2-Nitrophénol
88-75-5
2,4-Dinitrophénol
51-28-5
3-Nitrophénol
554-84-7
2,5-Dinitrophénol
329-71-5
4-Nitrophénol
100-02-7
2,6-Dinitrophénol
573-56-8
4-Méthyl-2-nitrophénol
119-33-5
2,4-Dinitro-6-méthylphénol
534-52-1
3-Méthyl-4-nitrophénol
2581-34-2
2,6-Diméthyl-4-nitrophénol
2423-71-4
5-Méthyl-2-nitrophénol
700-38-9
2,4-Dichloro-6-nitrophénol
609-89-2
3-Méthyl-2-nitrophénol
4920-77-8
2,6-Dichloro-4-nitrophénol
618-80-4
CAS = «Chemical Abstracts System» (Système d'abréviations chimiques).
Kakovost vode - Določevanje izbranih nitrofenolov - Metoda z ekstrakcijo na trdni fazi in plinsko kromatografijo z masno spektrometrijsko detekcijo (ISO 17495:2001)
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 17495:2003
01-september-2003
.DNRYRVWYRGH'RORþHYDQMHL]EUDQLKQLWURIHQRORY0HWRGD]HNVWUDNFLMRQDWUGQL
ID]LLQSOLQVNRNURPDWRJUDILMR]PDVQRVSHNWURPHWULMVNRGHWHNFLMR ,62
Water quality - Determination of selected nitrophenols - Method by solid-phase extraction
and gas chromatography with mass spectrometric detection (ISO 17495:2001)
Wasserbeschaffenheit - Bestimmung ausgewählter Nitrophenole - Verfahren mittels
Festphasenanreicherung und Gaschromatographie mit massenspektrometrischer
Detektion (ISO 17495:2001)
Qualité de l'eau - Dosage des nitrophénols sélectionnés - Méthode par extraction en
phase solide avec détection par chromatographie en phase gazeuse et spectrométrie de
masse (ISO 17495:2001)
Ta slovenski standard je istoveten z: EN ISO 17495:2003
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST EN ISO 17495:2003 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 17495:2003
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SIST EN ISO 17495:2003
EUROPEAN STANDARD
EN ISO 17495
NORME EUROPÉENNE
EUROPÄISCHE NORM
March 2003
ICS 13.060.50
English version
Water quality - Determination of selected nitrophenols - Method
by solid-phase extraction and gas chromatography with mass
spectrometric detection (ISO 17495:2001)
Qualité de l'eau - Dosage des nitrophénols sélectionnés - Wasserbeschaffenheit - Bestimmung ausgewählter
Méthode par extraction en phase solide avec détection par Nitrophenole - Verfahren mittels Festphasenanreicherung
chromatographie en phase gazeuse et spectrométrie de und Gaschromatographie mit massenspektrometrischer
masse (ISO 17495:2001) Detektion (ISO 17495:2001)
This European Standard was approved by CEN on 9 January 2003.
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 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 Management Centre has the same status as the official
versions.
CEN members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece,
Hungary, Iceland, Ireland, Italy, Luxembourg, Malta, Netherlands, Norway, Portugal, Slovak Republic, 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
© 2003 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 17495:2003 E
worldwide for CEN national Members.
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SIST EN ISO 17495:2003
EN ISO 17495:2003 (E)
Foreword
The text of ISO 17495:2001 has been prepared by Technical Committee ISO/TC 147 "Water
quality" of the International Organization for Standardization (ISO) and has been taken over as
EN ISO 17495:2003 by 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 September 2003, and conflicting national
standards shall be withdrawn at the latest by September 2003.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of
the following countries are bound to implement this European Standard: Austria, Belgium, Czech
Republic, Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy,
Luxembourg, Malta, Netherlands, Norway, Portugal, Slovak Republic, Spain, Sweden,
Switzerland and the United Kingdom.
Endorsement notice
The text of ISO 17495:2001 has been approved by CEN as EN ISO 17495:2003 without any
modifications.
NOTE Normative references to International Standards are listed in Annex ZA (normative).
2
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SIST EN ISO 17495:2003
EN ISO 17495:2003 (E)
Annex ZA
(normative)
Normative references to international publications
with their relevant European publications
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of
any of these publications apply to this European Standard only when incorporated in it by
amendment or revision. For undated references the latest edition of the publication referred to
applies (including amendments).
NOTE Where an International Publication has been modified by common modifications, indicated
by (mod.), the relevant EN/HD applies.
Publication Year Title EN Year
ISO 5667-1 1980 Water quality - Sampling - Part 1: EN 25667-1 1993
Guidance on the design of
sampling programmes
ISO 5667-2 1991 Water quality - Sampling - Part 2: EN 25667-2 1993
Guidance on sampling techniques
ISO 5667-3 1994 Water quality - Sampling - Part 3: EN ISO 5667-3 1995
Guidance on the preservation and
handling of samples
3
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SIST EN ISO 17495:2003
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SIST EN ISO 17495:2003
INTERNATIONAL ISO
STANDARD 17495
First edition
2001-08-15
Water quality — Determination of selected
nitrophenols — Method by solid-phase
extraction and gas chromatography with
mass spectrometric detection
Qualité de l'eau — Dosage des nitrophénols sélectionnés — Méthode par
extraction en phase solide avec détection par chromatographie en phase
gazeuse et spectrométrie de masse
Reference number
ISO 17495:2001(E)
©
ISO 2001
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SIST EN ISO 17495:2003
ISO 17495:2001(E)
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ii © ISO 2001 – All rights reserved
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SIST EN ISO 17495:2003
ISO 17495:2001(E)
Contents Page
Foreword.iv
Introduction.v
1 Scope .1
2 Normative references .1
3 Principle.2
4 Interferences .2
5 Reagents.3
6 Apparatus .5
7 Sampling.6
8 Procedure .6
9 Calibration .9
10 Calculation.12
11 Expression of results .14
12 Test report .14
Annex A (informative) Examples of suitable capillary columns.15
Annex B (informative) Examples of sorbents suitable for solid-phase extraction of nitrophenols .16
Annex C (informative) Precision data.17
Annex D (informative) Example of typical spectra.18
Bibliography.19
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SIST EN ISO 17495:2003
ISO 17495:2001(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 3.
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 International Standard may be the subject of
patent rights. ISO shall not be held responsible for identifying any or all such patent rights.
International Standard ISO 17495 was prepared by Technical Committee ISO/TC 147, Water quality,
Subcommittee SC 2, Physical, chemical and biochemical methods.
Annexes A to D of this International Standard are for information only.
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SIST EN ISO 17495:2003
ISO 17495:2001(E)
Introduction
Several methods may be applied to determine nitrophenols in water. This International Standard describes a gas
chromatographic/mass spectrometric determination after solid-phase extraction and derivatization with
diazomethane. It should be investigated whether and to what extent particular problems will require the
specification of additional marginal conditions.
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SIST EN ISO 17495:2003
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SIST EN ISO 17495:2003
INTERNATIONAL STANDARD ISO 17495:2001(E)
Water quality — Determination of selected nitrophenols — Method
by solid-phase extraction and gas chromatography with mass
spectrometric detection
WARNING — Persons using this International Standard should be familar with normal laboratory practice.
This International Standard does not purport to address all safety problems, if any, associated with its use.
It is the responsibility of the user to establish appropriate health and safety practices and to ensure
compliance with any national regulatory conditions.
1 Scope
This International Standard specifies a method for the determination of selected nitrophenols (see Table 1) in
1)
drinking, ground and surface water in mass concentrations � 0,5�g/l .
Table 1 — Nitrophenols to which this method is applicable
CAS No. CAS No.
2-Nitrophenol 88-75-5 2,4-Dinitrophenol 51-28-5
3-Nitrophenol 554-84-7 2,5-Dinitrophenol 329-71-5
4-Nitrophenol 100-02-7 2,6-Dinitrophenol 573-56-8
4-Methyl-2-nitrophenol 119-33-5 2,4-Dinitro-6-methylphenol 534-52-1
3-Methyl-4-nitrophenol 2581-34-2 2,6-Dimethyl-4-nitrophenol 2423-71-4
5-Methyl-2-nitrophenol 700-38-9 2,4-Dichloro-6-nitrophenol 609-89-2
3-Methyl-2-nitrophenol 4920-77-8 2,6-Dichloro-4-nitrophenol 618-80-4
CAS � Chemical Abstracts Service.
2 Normative references
The following normative documents contain provisions which, through reference in this text, constitute provisions of
this International Standard. For dated references, subsequent amendments to, or revisions of, any of these
publications do not apply. However, parties to agreements based on this International Standard are encouraged to
investigate the possibility of applying the most recent editions of the normative documents indicated below. For
undated references, the latest edition of the normative document referred to applies. Members of ISO and IEC
maintain registers of currently valid International Standards.
ISO 5667-1:1980, Water quality — Sampling — Part 1: Guidance on the design of sampling programmes.
ISO 5667-2:1991, Water quality — Sampling — Part 2: Guidance on sampling techniques.
1) See the results from the interlaboratory trial given in annex C.
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ISO 17495:2001(E)
ISO 5667-3:1994, Water quality — Sampling — Part 3: Guidance on the preservation and handling of samples.
ISO 8466-1:1990, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 1: Statistical evaluation of the linear calibration function.
3Principle
Solid-phase extraction of the nitrophenols is carried out from the acidified sample, followed by solvent elution,
derivatization with diazomethane and determination by gas chromatography and mass spectrometry.
It is absolutely essential that the tests described in this International Standard be carried out by suitably qualified
staff.
4 Interferences
4.1 Interferences during enrichment
In order to avoid losses, analyse the sample as soon as possible after sampling. If storage is unavoidable, store at
4�C until sample pretreatment.
The commercially available adsorbance materials are often of varying quality. Considerable batch-to-batch
variations in quality and selectivity of this material are possible.
The recovery may vary with the concentration, and shall therefore regularly be checked at different concentrations.
Calibration and analysis shall be performed with material from one and the same batch only.
Suspended matter in the water sample (such as iron hydroxide, calcium carbonate) occurring on sampling, storage
and sample preparation, as well as increased concentrations of microorganisms, may clog the packing. In this case
the water sample may be filtered through a glass-fibre filter prior to the enrichment. A filtration step shall be
mentioned in the test report.
Possible losses due to heating and volume reduction of the eluate may be reduced by the addition of a keeper (for
example iso-octane)
4.2 Interferences in the gas chromatograph
The operating conditions shall be set in accordance with the manufacturer's instructions. These settings shall be
checked at regular intervals.
General interferences, caused by the injection system or insufficient separation, can be eliminated with the help of
special laboratory experience and the instrument manuals.
Excess diazomethane may cause instrument failure or damage, due to its high reactivity. Therefore care should be
taken to remove excess diazomethane as far as possible by reducing the volume of the solution.
The use of alcohol as solvent should be avoided because any alcohol may destroy the deactivation layer (poly-
siloxane) of the glass liner, leading to column load and an overload of the detector. In this case, the quantification
of the analyte and the reproducibility of the result are no longer possible.
The stability of the analyte system should be checked (for example by application of a measuring standard).
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SIST EN ISO 17495:2003
ISO 17495:2001(E)
5 Reagents
Reagents “for residual analysis” shall be used. Impurities of the reagents and of the water contributing to the blank
shall be negligibly low. The blank shall be checked before use, especially prior to the use of a new batch.
5.1 Water, double-distilled or of comparable purity.
5.2 Operating gases for the gas chromatograph/mass spectrometer, in accordance with the manufacturer's
instructions.
The operating gases shall be of high purity.
5.3 Nitrogen, high purity, minimum 99,996 % (volume fraction), for drying and eventually for concentration by
evaporation.
5.4 Hydrochloric acid, c(HCl)�2mol/l.
5.5 Diethyl ether,C H O, stabilized only with ethanol.
4 10
5.6 Potassium hydroxide, KOH, aqueous solution, �� 0,6.
5.7 Ethanol,C H OH.
2 5
5.8 N-methyl-N-nitroso-4-toluenesulfonamide, (Diazald) C H N O S.
8 10 2 3
5.9 Acetic acid,CH COOH , aqueous solution, 10 % volume fraction (used to destroy diazomethane).
3
5.10 Solvents
5.10.1 Acetone, C H O.
3 6
5.10.2 Methanol,CH OH.
3
5.10.3 Ethyl acetate, C H O .
4 8 2
5.11 Methylated phenols
Reference substances as methylated substances according to Table 1, with defined concentrations for the
preparation of calibration solutions for gas chromatography (8.3)
5.11.1 Standard stock solution of methylated single substances
Weigh 50 mg of each of the reference substances into a 100-ml measuring flask, dissolve in ethyl acetate (5.10.3)
or acetone (5.10.1) and bring to volume with ethyl acetate or acetone.
Store the solution in a refrigerator (about 4 °C). The shelf-life is limited (about 3 months) and the concentration
shall be checked before use.
5.11.2 Intermediate standard solution of methylated single substances
Pipette into 100-ml measuring flasks 1 ml of the solution of the single substance (5.11.1), and bring to volume with
ethyl acetate or acetone.
Store the solution in a refrigerator (about 4�C). The shelf-life is limited (about 3 months) and the concentration
shall be checked before use.
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ISO 17495:2001(E)
5.11.3 Calibration solutions for multipoint calibration (methylated phenols).
Prepare the calibration solutions by adequate dilution of the stock solutions (5.11.2) with ethyl acetate (5.10.3).
Store the solution in a refrigerator (about 4 °C). Their shelf-life is limited (about 3 months) and their concentration
shall be checked regularly.
5.12 Reference substances
Reference substances (see Table 1) with defined concentrations for preparation of calibration solutions, for
determination of the recovery (9.5) and for calibration over the overall procedure (9.3).
5.12.1 Standard stock solutions of non-methylated phenols
Weigh 50 mg of each of the reference substances in a 100-ml measuring flask, dissolve with acetone (5.10.1) or
ethyl acetate (5.10.3) and bring to volume with ethyl acetate (5.10.3).
Store the solutions in a refrigerator (about 4 °C). Their shelf-life is limited (about 3 months) and their concentration
shall be checked before use.
5.12.2 Intermediate standard solutions of non-methylated phenols
Pipette into 100-ml measuring flasks 1 ml of the solution of the single substances (5.12.1), and bring to volume with
ethyl acetate (5.10.3)
Store the solutions in a refrigerator. Their shelf-life is limited (about 3 months) and their concentration shall be
checked before use.
5.12.3 Calibration solutions for multipoint calibration (non-methylated phenols)
Prepare the calibration solutions by adequate dilution of the intermediate standard solutions (5.12.2) with solvent.
Store the solutions in a refrigerator. Their shelf-life is limited (about 3 months) and their concentration shall be
checked regularly.
5.13 Diazomethane solution
WARNING — 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. Diazald and diazomethane should be regarded as toxic, carcinogenic
and mutagenic. Handle with care.
Diazomethane may be prepared in a distillation apparatus or in a commercially available equipment, preferably in a
fume cupboard. An example of a preparation method is as follows.
In a 250 ml reaction flask, add 8 ml of the KOH solution (5.6) and 10 ml of ethanol (5.7).
Dissolve 5,0 g of Diazald (5.8) in 45 ml of diethyl ether (5.5) in a filter funnel.
Cautiously warm the reaction flask to about 60�C (water bath) and, within 20 min, dropwise add the solution from
the filter funnel.
Collect the diazomethane being formed during this process and the diethyl ether in the cooled trap (cooling with
ice/NaCl).
After this reaction, add a further 10 ml of diethyl ether through the filter funnel and distil the remaining
diazomethane.
Stopper the trap and store at about� 18�C for not longer than 1 month.
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SIST EN ISO 17495:2003
ISO 17495:2001(E)
Glassware used in the preparation of diazomethane or which has come into contact with Diazald should be cleaned
with a 10 % aqueous solution of acetic acid (5.9). It is advisable to clean the apparatus after rinsing the filter funnel
and the reaction flask by distillation of about 50 ml of ethanol (5.7).
5.14 Internal standards
As internal standards, use two of the following phenols:
2,4-Dibromophenol, C H OBr , CAS No. 615-58-7
6 4 2
2,6-Dibromophenol, C H OBr , CAS No. 608-33-3
6 4 2
2,3,6-Trichlorophenol, C H OCl , CAS No. 933-75-5
6 3 3
2,4,6-Tribromophenol, C H OBr , CAS No. 118-79-6
6 3 3
13
Deuterated or C-labelled substances are suitable as well.
NOTE The internal standards are used for the control of the analytical procedure. The choice of the substances depends
on the expected phenols to be determined.
Prepare a mixed standard solution of the two components in a concentration which gives peak heights in the upper
part of the linear range.
Usually, a concentration of 10�g/ml is suitable; check the concentration prior to use.
6 Apparatus
Equipment or parts of it which may come into contact with the water sample or its extract should be free from
residues causing significant blanks. It is recommended to use vessels made of glass or stainless steel.
6.1 Flat-bottomed flasks, preferably brown glass, 1 000 ml and 2 000 ml, with glass stoppers.
6.2 Cartridges, made of polypropene or glass, filled with solid-phase material, e.g. styrene/divinylbenzene
polymer (see annex B).
6.3 Vacuum or pressure assembly for the enrichment step.
6.4 Measuring flasks, or graduated flasks with inert stopper, for the eluates.
In the case of autosampling, vials shall be made from glass and the septum covered with polytetrafluoroethene
(PTFE).
6.5 Apparatus for preparing diazomethane, comprising:
� double-necked round-bottomed flask, 250 ml;
� filter funnel, 100 ml;
� distillation column, e.g. Vigreux column;
� distillation head;
� condenser, e.g. Liebig condenser;
� flask for absorption of diazomethane;
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SIST EN ISO 17495:2003
ISO 17495:2001(E)
� security flask;
or a commercial distillation apparatus, preferably with fire-polished connections.
NOTE A closed system allows for a safer preparation of diazomethane.
6.6 Capillary gas chromatograph, equipped with a mass-spectrometric detector operated in the electron
impact mode, gas supply according to the manufacturer.
The mass spectrometer should be capable of operating across the mass range of interest and incorporate a data
system capable of quantifying ions using selected m/z values.
6.7 Injector, equipped for application with or without splitting, through-septum or on-column technique, or with
temperature programming.
6.8 Capillary columns for gas chromatography (see examples in Table A.1).
6.9 Glass-fibre filters, made of borosilicate glass, fibre diameter e.g. 0,75�mto 1,5�m, with inorganic binding
material.
6.10 Injection syringes, nominal capacity 5�lor10�l.
7 Sampling
Collect samples in accordance with ISO 5667-1, 5667-2 and 5667-3.
Use for sampling carefully cleaned, preferably brown flat-bottomed glass flasks, of capacity 250 ml or 1 000 ml.
Add 2 ml of hydrochloric acid (5.4) and fill to the brim with the sample.
In the case of possible presence of oxidizing agents, especially in presence of chlorine, add 1 g of sodium sulfite
(Na SO ) per 1 000 ml of sample.
2 3
The pH shall be� 2, if not, add more hydrochloric acid (5.4).
Prior to analysis, store the samples in the refrigerator. Storage time shall not exceed 3 days.
8 Procedure
8.1 Solid-phase enrichment
8.1.1 Pretreatment
As a rule, cartridges of 3 ml (sorbent mass 0,2 g) are suitable (see annex B for examples of suitable sorbents).
Condition the cartridges as follows:
a) Add 3 ml of ethyl acetate (5.10.3) , wait for 5 min, subsequently let it run dry.
b) Add 3 ml of methanol (5.10.2), and do not let it run dry.
c) Replace the methanol by 10 ml of water (5.1), acidified to pH 2. Do not let the cartridge run dry.
NOTE The size of the cartridges (volume, sorbent) depends on the mass concentration of phenols and the content of other
organic substances present.
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8.1.2 Enrichment
Start the enrichment immediately after conditioning.
Make sure that no air bubbles are trapped in the sorbent bed when changing from rinsing solution to sample.
Let a defined volume of the sample run through the column with a flowrate of 3 ml/min to 5 ml/min, make sure that
the flowrate remains constant.
Rinse the sorbent with 10 ml of water (5.1), acidified to pH 2, and subsequently dry with nitrogen (5.3) at a flowrate
of about 7 ml/s for at least 10 min.
NOTE The drying procedure may last up to 1 h. The end of the procedure is normally recognized by a brightening of the
sorbent.
8.1.3 Elution
Elute with 2 ml of ethyl acetate (5.10.3), add the solvent in small portions at intervals of about 1 min.
Concentrate the eluate to about 0,5 ml using nitrogen (5.3) at room temperature.
NOTE As a rule and in case of dry sorbent, only 1 ml of ethyl acetate will allow complete elution. Larger volumes of
solvents, or combinations of solvents, may be used if it is expected that the sorbent cannot be dried within a reasonable time. In
these cases it may be advantageous to carry out a pre-elution with a small amount of methanol. This should be stated in the test
report.
8.2 Derivatization with diazomethane
Add a sufficient volume of diazomethane solution (about 200�l to 500�l) (5.13), stopper the flask and allow the
reaction to proceed in the dark.
After the reaction is complete (about 30 min; solution stays yellow), evaporate the solution with nitrogen (5.3) to a
volume not smaller than 200�l.
NOTE The addition of a keeper (e.g. about 0,05 ml of iso-octane) may be helpful to avoid losses during evaporation.
In the case of calibration with an external standard, bring the solution to volume with ethyl acetate (5.10.3).
8.3 Gas chromatography
Optimize the instrument parameters as described in the operator's manual.
Capillary columns with almost non-polar or non-polar stationary phases based on methyl silicones are especially
suitable (see Table A.1). Depending on the case, a semi-polar or polar column may be helpful.
Use a mass spectrometric detector.
Record mass spectra in the full-scan mode for a relevant mass range within 35 m/z and 260 m/z, with the upper limit
at least 10 m/z above the hi
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