SIST EN ISO 15680:2004

SLOVENSKI STANDARD
01-februar-2004
.DNRYRVWYRGH±'RORþHYDQMHPRQRFLNOLþQLKRJOMLNRYRGLNRYQDIWDOHQDLQ
SRVDPH]QLKNORULUDQLKVSRMLQVSOLQVNRNURPDWRJUDILMR]XSRUDERWHKQLNHSXUJH
DQGWUDSLQWRSORWQRGHVRUSFLMR,62
Water quality - Gas-chromatographic determination of a number of monocyclic aromatic
hydrocarbons, naphthalene and several chlorinated compounds using purge-and-trap
and thermal desorption (ISO 15680:2003)
Wasserbeschaffenheit - Gaschromatische Bestimmung einer Anzahl monocyclischer
aromatischer Kohlenwasserstoffe, Naphthalin und einiger chlorierter Substanzen mittels
Purge und Trap und thermischer Desorption (ISO 15680:2003)
Qualité de l'eau - Dosage par chromatographie en phase gazeuse d'un certain nombre
d'hydrocarbures aromatiques monocycliques, du naphtalene et de divers composés
chlorés par dégazage, piégeage et désorption thermique (ISO 15680:2003)
Ta slovenski standard je istoveten z: EN ISO 15680:2003
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.

EUROPEAN STANDARD
EN ISO 15680
NORME EUROPÉENNE
EUROPÄISCHE NORM
November 2003
ICS 13.060.50
English version
Water quality - Gas-chromatographic determination of a number
of monocyclic aromatic hydrocarbons, naphthalene and several
chlorinated compounds using purge-and-trap and thermal
desorption (ISO 15680:2003)
Qualité de l'eau - Dosage par chromatographie en phase Wasserbeschaffenheit - Gaschromatische Bestimmung
gazeuse d'un certain nombre d'hydrocarbures aromatiques einer Anzahl monocyclischer aromatischer
monocycliques, du naphtalène et de divers composés Kohlenwasserstoffe, Naphthalin und einiger chlorierter
chlorés par dégazage, piégeage et désorption thermique Substanzen mittels Purge und Trap und thermischer
(ISO 15680:2003) Desorption (ISO 15680:2003)
This European Standard was approved by CEN on 28 October 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, Slovakia, 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 15680:2003 E
worldwide for CEN national Members.

CORRECTED 2003-12-17
Foreword
This document (EN ISO 15680:2003) 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 May 2004, and conflicting national standards
shall be withdrawn at the latest by May 2004.
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, Slovakia, Spain, Sweden, Switzerland and
the United Kingdom.
Endorsement notice
The text of ISO 15680:2003 has been approved by CEN as EN ISO 15680:2003 without any
modifications.
NOTE Normative references to International Standards are listed in Annex ZA (normative).
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 3696 1987 Water for analytical laboratory EN ISO 3696 1995
use - Specification and test
methods
INTERNATIONAL ISO
STANDARD 15680
First edition
2003-11-01
Water quality — Gas-chromatographic
determination of a number of monocyclic
aromatic hydrocarbons, naphthalene and
several chlorinated compounds using
purge-and-trap and thermal desorption
Qualité de l'eau — Dosage par chromatographie en phase gazeuse
d'un certain nombre d'hydrocarbures aromatiques monocycliques, du
naphtalène et de divers composés chlorés par dégazage, piégeage et
désorption thermique
Reference number
ISO 15680:2003(E)
©
ISO 2003
ISO 15680:2003(E)
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ii © ISO 2003 — All rights reserved

ISO 15680:2003(E)
Contents Page
Foreword. iv
1 Scope. 1
2 Normative references. 1
3 Terms and definitions. 2
4 Principle. 2
5 Interferences. 3
6 Reagents. 4
7 Apparatus. 7
8 Sample collection, preservation and preparation . 8
9 Analytical procedure. 9
10 Calibration. 11
11 Calculation. 12
12 Expression of results. 12
13 Precision data. 12
14 Test report. 12
Annex A (informative) Application of purge-and-trap concentration to the GC analysis of volatile
compounds in water — Example 1: Validation study in the UK. 14
Annex B (informative) Application of purge-and-trap concentration to the GC-analysis of volatile
compounds in water — Example 2: Data provided by DIN. 19
Annex C (informative) Application of purge-and-trap concentration to the GC-analysis of volatile
compounds in water — Example 3: Validation study in the Netherlands. 22
Annex D (normative) Criteria for the GC-MS identification of target compounds. 25
Annex E (informative) Procedures for the cleaning of glassware and the preparation of
contaminant-free water. 28
Annex F (informative) Preparation of standard solutions of volatile organic compounds . 30
Annex G (informative) Determination of the (absolute) recovery of substances analysed by
purge-and-trap concentration. 32
Bibliography . 33

ISO 15680:2003(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 15680 was prepared by Technical Committee ISO/TC 147, Water quality, Subcommittee SC 2, Physical,
chemical and biochemical methods.

iv © ISO 2003 — All rights reserved

INTERNATIONAL STANDARD ISO 15680:2003(E)

Water quality — Gas-chromatographic determination of a
number of monocyclic aromatic hydrocarbons, naphthalene
and several chlorinated compounds using purge-and-trap and
thermal desorption
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.
1 Scope
This International Standard specifies a general method for the determination of volatile organic compounds
(VOCs) in water by purge-and-trap isolation and gas chromatography (GC). Annexes A, B and C provide
examples of analytes that can be determined using this International Standard. They range from
difluorodichloromethane (R-12) up to trichlorobenzene, including all non-polar organic compounds of
intermediate volatility.
Detection is preferably carried out by mass spectrometry in the electron impact mode (EI), but other detectors
may be applied as well.
The limit of detection largely depends on the detector in use and the operational parameters. Typically
1)
detection limits as low as 10 ng/l can be achieved. The working range typically is up to 100 µg/l.
This International Standard is applicable to drinking water, ground water, surface water, seawater and to
(diluted) waste water.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO 3696, Water for analytical laboratory use — Specifications and test methods
ISO 5667-3, Water quality — Sampling — Part 3: Guidance on the preservation and handling of water
samples
ISO 8466-1, Water quality — Calibration and evaluation of analytical methods and estimation of performance
characteristics — Part 1: Statistical evaluation of the linear calibration function

1) The value given is an indication of the limit of detection. It is calculated as 3 times the standard deviation of a series of
measurements of 10 replicate samples under conditions of repeatability.
ISO 15680:2003(E)
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1
volatile organic compound
VOC
organic compound, generally non-polar, with boiling point between approximately −30 °C and 220 °C
3.2
target compound
selected component whose presence or absence is determined
NOTE This definition can also apply to a derivative of the original compound which is formed during an intentional
derivatization procedure.
3.3
standard compound
target compound with the highest possible purity that can be used as a reference during the analysis and free
of impurities having any influence on its mass spectrum
3.4
retention-time standard
compound that is added to the sample (or to the sample extract) and to the external standard solution (3.6)
and whose retention time is used to calculate the relative retention times of the target compounds
NOTE The retention-time standard may be identical to the internal standard(s).
3.5
relative retention time
ratio between the retention time of the target compound and the retention time of the retention-time standard
3.6
external standard solution
solution of a known concentration of the target compounds
3.7
lowest concentration for identification
lowest concentration of the target compound which, if present in the sample, still can be identified using the
identification criterion that the selected diagnostic ion with the lowest intensity is still present in the mass
spectrum with a signal-to-noise ratio higher than 3:1
NOTE This concentration strongly depends on the sensitivity of the instrument and on the performance
characteristics of the analytical method.
3.8
diagnostic ion
ion selected from the mass spectrum of the target compound with the highest possible specificity
NOTE For the selection of diagnostic ions, see D.5.
4 Principle
A fixed volume of sample is purged with a fixed volume of an inert gas to strip out the volatile components
which are subsequently trapped. This trapping can be either:
a) on a packed adsorbent trap (preferably combined with or followed by a cryofocusing system), or
b) directly on a capillary cold-trap.
2 © ISO 2003 — All rights reserved

ISO 15680:2003(E)
After completion of the purge process, the trap is heated to desorb the volatile components which are swept
by the GC carrier gas on to a capillary GC column. This transfer to the GC column can be done in an on-line
or in an off-line set-up. To achieve narrow injection bandwidths, the use of a cryofocusing system is
recommended when the trapping is done on a packed adsorbent trap as in a) or the transfer is done through
an injector-splitter set at approximately 20:1 if the sensitivity of the analytical system allows this.
The components are separated by GC utilizing temperature programming, and are detected by the use of a
mass spectrometer. Data are acquired in the full-scan mode or at a sufficient number of specific fragments to
enable matching against those of the standards. A compound is regarded to be present when the criteria of
Annex D are met. Quantification is carried out using selected characteristic fragments for each determinand.
5 Interferences
5.1 General
In principle, any purgeable compound which elutes at the same chromatographic retention time and produces
a mass spectrum identical, or very similar, to any determinand under investigation will interfere. In practice,
this is unlikely as the spectra of most of the determinands are characteristic. With retention-time data and the
availability of the spectrum over a wide range of masses, the possibility of misidentification is quite small. Co-
eluting peaks with ions with non-specific m/z values might cause interference, but quantification ions can be
chosen to preclude this.
Contamination introduced during the analytical procedure is monitored by the determination of blanks (9.4).
5.2 Interferences in the sampling process
VOCs are amenable to evaporation or degassing during the sampling process, transportation, storage and
preparation of the samples. This can result in measured concentrations which are too low. VOCs can also
diffuse into the samples from the ambient air of the laboratory or from air in the refrigerator where samples are
stored. This results in concentrations which are too high.
5.3 Interferences due to the purge gas and the GC gas
Insufficient purity of the purge gas or the GC carrier gas can cause interferences.
5.4 Interferences in the purge-and-trap process
One of the main sources of contamination during sample transportation is contaminated laboratory air in the
purge vessel or sample container. Therefore, the laboratory should be free of solvents and concentrated
standard solutions.
Laboratory clothing is also a potential source of contamination, particularly of highly volatile halogenated
hydrocarbons.
To avoid interferences, all materials (tubing, seals, valves, etc.) should be made from stainless steel or glass.
The use of plastics material should be avoided. All glassware directly in contact with the sample or purged
compounds should be cleaned thoroughly (see Annex E). There is an especially high risk of entrainment after
the measurement of highly polluted samples.
Purge vessels incorporating a glass frit are liable to cause cross-contamination (see also 7.1).
Purging of water samples containing surfactants can result in formation of foam which might be in direct
contact with the adsorbent. If this occurs, the purge procedure shall be stopped immediately.
ISO 15680:2003(E)
5.5 Interferences in the thermal desorption process
During thermal desorption, substances can degrade.
The transfer lines between the adsorption trap and the gas chromatography injection system should not have
any “cold” points which act as adsorbents, as this results in a loss of VOCs.
When using a cryofocusing system and if the adsorbents are not completely dried after the purge process, the
capillaries can block with ice. This results in incomplete desorption, and evaluation of the analytical procedure
will be impossible.
The adsorbents used in the purge-and-trap systems are subject to ageing (contamination, thermal stress)
which can cause changes in the trapping capacity and in the blank values.
5.6 Interferences in automatic samplers
Samples in autosamplers intended for subsequent analysis shall be protected from light (e.g. by use of brown
glass vials).
Special care should be taken for autosamplers with respect to the remarks made under 5.4.
6 Reagents
Use reagents of sufficient purity that do not give rise to interfering peaks in the gas chromatographic analysis.
Check freshly prepared standard solutions against previously prepared standard solutions to ensure for
standard integrity. This should be checked with each batch of material by analysing procedural blank solutions
with each batch of samples. Use solvents of high quality that do not contain interfering compounds and
analytical reagent grade materials, as far as available. Reagents may contaminate by contact with air and/or
other materials, particularly plastics, or by degradation caused by reaction with light. Reagents should be
stored in all-glass containers or other vessels found to be suitable, and kept in the dark, if necessary.
6.1 Water, used for blank determination, dilution of samples and for the preparation of calibration solutions.
Water should be known to be free from contaminants (see Annex E). It should show negligible interferences in
comparison with the smallest concentration to be determined, in accordance with ISO 3696.
A sufficient amount of water from the same batch should be available to complete each batch of analyses,
including all preparations.
6.2 Methanol, CH OH, used as solvent, and for the preparation of standard stock solutions.
Other solvents that are readily soluble in water and do not interfere with the analytical process can be used as
well. This includes N,N-dimethylformamide (DMF, C H NO), dimethyl sulfoxide (DMSO, C H SO) and
3 7 2 6
acetone (C H O).
3 6
6.3 Sodium thiosulfate pentahydrate, Na S O ⋅5H O.
2 2 3 2
If necessary, add sodium thiosulfate to samples to remove remaining oxidants like chlorine or ozone. Other
non-interfering substances may be used for the same purpose (e.g. sodium sulfite).
NOTE Already formed intermediate oxidation products like halogenated acetic acids can still form trihalomethanes
regardless of the preservation described in this clause.
6.4 Sodium hydrogensulfate, NaHSO .
Other suitable diluted acids or acid salts may be used as well.
4 © ISO 2003 — All rights reserved

ISO 15680:2003(E)
6.5 Purge gas.
Use a high quality helium or nitrogen gas for purging, free of interfering substances. Impurities can be
eliminated by a purification cartridge, if necessary.
6.6 Standard solutions.
Owing to the high volatility of the gases and the more volatile compounds to be analysed, great care is
required in the preparation of standard solutions; losses may occur in the headspace of the vessel used to
prepare standard solutions. For a detailed description of the preparation of standard stock solutions of volatile
compounds see Annex F. It is advisable, and more appropriate, to use commercially available standard
solutions. Store intermediate standard solutions at about 4 °C and allow them to reach room temperature
before use.
Whilst the following procedures are given as examples, users may wish to prepare their own standard
solutions by an alternative procedure or by diluting commercially available stock solutions (preferably certified),
which are shown to produce equivalent results.
6.6.1 Stock calibration standard solution (2 mg/ml).
Dissolve defined quantities of approximately 200 mg of each VOC in a 100 ml volumetric flask partially filled
with the same solvent (6.2), make up to the mark and mix well. See also Annex F.
6.6.2 Stock internal standard solutions (2 mg/ml).
Dissolve defined quantities of approximately 200 mg of each internal standard compound in a 100 ml
volumetric flask partially filled with the same solvent (6.2), make up to the mark and mix well. See also
Annex F.
At least one internal standard compound should be used for quantitation and additional internal standard
compounds could be used as surrogate standards. Suitable compounds may be selected from Table 1. Use
deuterated standards only for GC-MS. For the indicated internal standard compounds (*) of Table 1, the range
of analytes covered by each of them is given in Annex A as an example (Table A.2).
6.6.3 Spiking solutions.
Prepare spiking solutions from solutions 6.6.1 and 6.6.2 by appropriate dilution in a volumetric flask containing
the same solvent (6.2). As an example, Table 2 gives a dilution scheme in 100 ml of solvent and consecutive
spiking of 5 µl of it to 100 ml water to give spiking solutions 6.6.3.1 to 6.6.3.6. In this example, analyte
concentrations range from 0 µg/l to 5 µg/l in water.
If the desired measuring range differs from that of Table 2, different dilution ratios should be taken or the
spiking volume should be adapted.
NOTE Solution 6.6.3.1 is used as the internal standard solution to be added to each sample (see 9.3).
6.6.4 Calibration solutions.
Add a small volume of the spiking solutions 6.6.3.2. to 6.6.3.6 from Table 2 to the water (6.1) in the purge
vessel (7.1) [or in the sample container (7.3) when an autosampler is used]. Table 2 gives an example of a
5 µl addition to 100 ml of water (with concentrations as indicated in the fourth column). If larger sample
volumes are analysed, add an equivalently larger volume of spiking solution.
Make sure that the content of the organic solvent in the final aqueous calibration standard solution does not
exceed 2 % (volume fraction). If a high percentage of solvent is present, linearity should be checked.
6.6.5 Blank solution.
Reserve a portion of the unspiked water for use as a quality control blank.
ISO 15680:2003(E)
Table 1 — Internal standard compounds
CAS-RN Compound Formula
462-06-6 * monofluorobenzene C H F
6 5
3114-55-4 * monochlorobenzene-d C CID
5 6 5
3855-82-1 * 1,4-dichlorobenzene-d C Cl D
4 6 2 4
540-36-3 * 1,4-difluorobenzene C H F
6 4 2
460-00-4 1-bromo-4-fluorobenzene C H BrF
6 4
2037-26-5 toluene-d C D
8 7 8
1868-53-7 dibromofluoromethane CHBr F
109-70-6 1-bromo-3-chloropropane C H BrCl
3 6
107-04-0 1-bromo-2-chloroethane C H BrCl
2 4
75-62-7 bromotrichloromethane CBrCl
363-72-4 pentafluorobenzene C HF
6 5
1076-43-3 benzene-d C D
6 6 6
17060-07-0 1,2-dichloroethane-d C Cl D
4 2 2 4
20302-26-5 ethylbenzene-ring-d C H D
5 8 5 5
74-97-5 bromochloromethane CH BrCl
3017-95-6 2-bromo-1-chloropropane C H BrCl
3 6
110-56-5 1,4-dichlorobutane C H Cl
4 8 2
56004-61-6 o-xylene-d C D
10 8 10
* Range of analytes covered is given in Table A.2
Table 2 — Dilution scheme in 100 ml solvent
ml of 6.6.2 ml of 6.6.1 Concentration (in µg/l) in
Analyte concentration in
Spiking solution (added to (added to calibration solution (5 µl of
spiking solution (in mg/l of
(100 ml of solvent) 100 ml of 100 ml of spiking solution added to
solvent)
a
solvent) solvent) 100 ml of water)
6.6.3.1 5 0 0 0
6.6.3.2 5 1 20 1
6.6.3.3 5 2 40 2
6.6.3.4 5 3 60 3
6.6.3.5 5 4 80 4
6.6.3.6 5 5 100 5
a
The concentration of the internal standard compound in each spiking solution is 100 mg/l.
6 © ISO 2003 — All rights reserved

ISO 15680:2003(E)
7 Apparatus
Usual laboratory glassware and equipment is not specified, as the actual devices used depend on the specific
application and circumstances. Make sure that all devices are free of interfering compounds. Clean all
glassware, including sample bottles, thoroughly. A standard procedure for cleaning is included in Annex E.
7.1 Purge vessels
A variety of purge vessels are commercially available. The specific type is defined by the purge-and-trap
apparatus in use. There are systems available which allow purging in the sampling vessels. Cleaning of the
purge vessels should be carried out according to Annex E.
7.2 Sample containers
Various sample containers can be used, e.g. screw-cap containers fitted with PTFE-faced silicone discs. For
purge-and-trap systems with an autosampler, use sample containers recommended by the autosampler
manufacturer. Whenever septa are employed, do not re-use them.
7.3 Purge-and-trap apparatus
Purge-and-trap apparatus is commercially available or can be self-constructed. This includes fully automated,
on-line purge-and-trap GC-equipment with an autosampler and the thermal desorption device incorporated in
the instrument, as well as manually operated off-line equipment. All instruments may be used that meet the
requirements and have proven to give reliable results. According to Annexes A, B and C, various instruments
have been used. Other devices may be suitable but should be examined appropriately to ensure satisfactory
performance.
The purge-and-trap apparatus should include:
a) autosampler;
b) purge vessel, heating mantle and temperature control, purge gas supply, flowrate control, timer;
c) condenser and coolant supply or dry-purge system;
d) adsorbent trap;
e) thermal desorption device, temperature control, timer;
f) cold trap, coolant supply, heater, temperature control;
g) GC-MS or a GC with suitable detector(s), GC-auxiliaries, data system.
Various combinations of components a), c), d), e) and f) are possible and don’t all need to be included.
7.4 Adsorbent trap
7.4.1 For purge-and-trap apparatus using intermediate trapping on a packed adsorption column (see
Clause 4), these traps are often home-made or can be obtained in various modifications. As an example,
adsorption columns are made of glass or stainless steel with an internal diameter of 2 mm to 5 mm,
appropriate for use in the apparatus for thermal desorption. Adsorbent traps are packed with a suitable
adsorbent.
ISO 15680:2003(E)
2)
Generally a polymer, a carbonaceous or silica adsorbent is used . Typical dimensions of the packing are
diameter 2 mm to 5 mm, length 10 mm to 50 mm, corresponding to at least 90 mg of adsorbent. The
adsorbent is kept in position by inert material such as glass wool plugs or glass screens. This description is an
example; other adsorbent traps can be used as well, provided their performance meets the requirements of
this International Standard.
Prior to their first use, adsorbent traps should be conditioned by heating them above their desorption
temperature for approximately 30 min while passing a gentle stream of inert gas through them. A blank
procedure shall be performed with the conditioned adsorbent trap before using it in routine.
7.4.2 Special requirements for use in off-line purge-and-trap equipment may apply.
In off-line purge-and-trap equipment, the adsorbent traps are not defined by the instrument in use, whereas
most of the other parts under 7.3 a) to f) are. For off-line use, mark the traps on one side to allow desorption in
a back-flush mode. In case of off-line purge-and-trap, for the adsorbent traps use caps of inert material, for
example PTFE, or of metal with screw windings and a PTFE-washer, so that after purging they can be closed
leakproof for storage or transfer to the apparatus for thermal desorption.
7.5 Gas chromatograph-mass spectrometer (GC-MS)
A variety of gas chromatographic columns can be used in purge-and-trap analysis. Examples of suitable
columns are given in Annexes A, B and C.
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. See Annexes A, B and C for typical
chromatograms.
Other GC detectors, such as flame ionization detector (FID), electron capture detector (ECD), photo-ionization
detector (PID) or electrolytic conductivity detector (ELCD), can be used, depending on the substances to be
analysed (see 9.7.2).
For operational aspects of the instruments, the manufacturer’s instructions should be followed.
8 Sample collection, preservation and preparation
Collect samples in accordance with ISO 5667-3 in suitable containers, preferably directly into the sample
containers (7.3). It is advisable to take two samples, one to be retained in the event of a repeat analysis being
required. Fill sample containers, avoiding turbulence, until overflowing. Cap sample containers without leaving
a headspace. For samples containing free chlorine or any other strong oxidant, solid sodium thiosulfate
pentahydrate (6.3) or other reducing salt should be added to the container (approximately 100 mg/l).
Additionally, for the preservation of aromatic compounds in surface waters, the pH should be lowered to 2
using sodium hydrogensulfate (6.4). Other appropriate acids are allowed.
Samples shall not be diluted if the concentration exceeds the working range established by the calibration
function, as dilution can cause evaporative losses of the analytes. Preferably extend the calibration function or
[1] [2]
apply (static) headspace analysis, e.g. according to ISO 10301 and/or ISO 11423-1 . Avoid contamination
of the equipment by dirty samples.
The stability of certain determinands is known to be matrix-dependent. Therefore, if the matrix of the sample
has not been evaluated, it is recommended that the sample be analysed preferably on the day of sampling
and not later than 5 days from sampling. Until analysis, store samples at about 4 °C and protected from direct
sunlight in air-tight closed containers.

2) Tenax, Porapak, Carbopak and Chromosorb are examples of typical adsorbents available commercially. This
information is given for the convenience of users of this International Standard and does not constitute an endorsement by

ISO of these products.
8 © ISO 2003 — All rights reserved

ISO 15680:2003(E)
If the water samples were not originally taken in the sample containers for the autosampler, or if the sample is
transferred manually into the purge vessel, pour a suitable volume of the sample gently into the respective
container or vessel without turbulence or withdraw the sample using an all-glass syringe, avoiding the release
of gas bubbles. Close the container immediately to avoid losses of the most volatile compounds.
Care should be taken if subsamples are taken with a syringe, as a partial vacuum can form, resulting in a
change in the concentration of volatile components in the sample.
If severe foaming occurs, the application of antifoam agents shall be considered. Alternatively, the sample
shall be analysed by static headspace or liquid extraction, if possible.
9 Analytical procedure
9.1 General
Depending on the instrumentation in use, deviations from the described procedure are allowed. This refers in
particular to the working conditions of the purge-and-trap procedure. All conditions for the measurement of
samples and for calibration should be identical.
9.2 Preparation
Set up the instrument(s) in accordance with the manufacturer’s instructions. If an autosampler is used, load it
with samples, calibration solutions (6.6.4) and blanks (6.6.5). If both clean and heavily contaminated samples
are to be analysed in the same series, it is recommended to process the clean samples first because of the
possible carry-over effects. To monitor carry-over, process blank samples directly after the contaminated ones.
Prepare fresh calibration solutions (6.6.4) in the respective concentration range.
9.3 Addition of internal standards
Add the internal standard to the samples and blanks by taking a proper aliquot of spiking solution (6.6.3) with
a syringe and immerse it underneath the water level of the sample. Ensure that no headspace losses of the
sample occur.
NOTE Some commercially available instruments automatically add the internal standard to the samples.
9.4 Blanks
Treat blanks (6.6.5) in the same way as the samples. At least one blank determination should be performed
prior to analysing real samples, in order to judge the performance of the entire procedure with respect to
contamination. The blank should not exceed 10 % of the lowest calibration solution or of the lowest level of
interest.
9.5 Quality control samples
As there are no additional possibilities to control the total analytical procedure, the analysis of sufficient quality
control samples is essential. This includes spiked samples.
Treat quality control samples as real samples, according to the laboratory's quality system. Evaluate the
results, e.g. on the basis of control charts.
9.6 Purge-and-trap concentration of the sample
Optimum working conditions can differ for each substance. Method development and validation should
provide appropriate values for the operational parameters in accordance with the specific application and
ISO 15680:2003(E)
instrument. The data below show average practical values. Examples of actual working conditions are given in
Annexes A, B and C.
The desired working range of the method, and more specifically the lowest detection limit, largely determines
the required sample volume. To achieve a fairly constant recovery, the total volume of purge gas (purge
time × flowrate) should be proportional to the sample volume. A ratio of approximately 10:1 (ml purge gas:ml
sample) generally is most practical, i.e. a sample volume of 20 ml purged by a gas flowrate of 10 ml/min for
20 min. Prolonged purging can improve the recovery of less volatile or slightly polar compounds. The optimum
purge time and gas flow rate for such compounds should be determined experimentally.
In general, a small sample volume is preferred to reduce analysis time and costs.
Purging at elevated temperatures is recommended for the analysis of less volatile or slightly polar compounds
as this will considerably improve the recovery. To prevent blocking of the cold trap by ice, remove the
entrained water vapour from the purge gas stream after it passes the purge vessel and prior to cryofocusing
onto the cold trap. This can be done for instance by the application of a condenser (at e.g. −10 °C) placed
between the purge vessel and the cold trap and/or by intermediate trapping onto an adsorption column filled
with a hydrophobic sorbent and/or by a dry purge step of the adsorbent trap prior to desorption. This way
purge temperatures as high as 95 °C can be used (see Annex C).
If an adsorbent trap (7.4) is incorporated in the purge-and-trap apparatus, the adsorption of purged
compounds is, in general, carried out at room temperature. Thermal desorption is done at the maximum
allowable temperature for the sorbent in use, generally between 200 °C and 250 °C for 5 min to 10 min.
When applying a cold trap, its temperature shall be low enough to condense the analytes quantitatively. The
temperature shall be about 70 °C below the boiling point of the most volatile analyte. Cold traps using liquid
carbon dioxide may be used down to −50 °C. Cold traps using liquid nitrogen may be used down to −120 °C.
Inject the analytes by flash desorption at 200 °C to 250 °C.
9.7 GC-MS analysis
9.7.1 General
Optimize the instrumental parameters in accordance with the manufacturer's instructions.
Determine the appropriate GC oven temperature programme experimentally during method development and
validation. The upper temperature should be higher than the desorption temperature of the adsorption column
and the flash desorption temperature of the cold trap.
Record mass spectra in the full-scan mode for a relevant mass range within 35 u and 300 u, with the upper
limit at least 10 u above the highest molecular mass of interest. Set the electron energy at approximately
−70 eV. If for the sake of sensitivity, only selected ions are detected, register at least three diagnostic ions,
preferably of the highest u-values. Additional MS operational aspects are given in Annex D.
Identify the compounds on the basis of their retention times and mass spectra. Criteria for GC-MS
identification are given in Annex D.
9.7.2 Alternative detectors
Alternatively, use an electron capture detector (ECD) or an electrolytic conductivity detector (ELCD, Hall
detector) to detect halogenated hydrocarbons. The sensitivity of an ECD varies with the nature of the analyte,
and it can be more sensitive than MS for tri- or tetra-halogenated compounds. A flame ionization detector
(FID) can be used as a universal detector for hydrocarbons (aliphatic, aromatic and halogenated) and a photo-
ionization detector (PID) can be used for the detection of aromatic compounds. The atomic emission detector
(AED) is an element-specific detector that can be used in this method. By the combination of the results from
several element traces, a high reliability for the compound identification can be established.
10 © ISO 2003 — All rights reserved

ISO 15680:2003(E)
When detectors other than MS are used, separation on two capillary columns of different polarity should be
considered in order to reduce the risk of false positive results by overlapping peaks. When using two columns,
the retention times on both columns should match with those of the standard. The lower concentration is then
accepted as being the most accurate value.
10 Calibration
Perform the calibration using one or more internal standard compounds. If target compounds are spread over
wide retention-time values, use different internal standards in accordance with D.2 in Annex D and Table A.2
in Annex A.
As a minimum, perform a five-point calibration by analysis of each of the calibration solutions (6.6.4), evenly
distributed over the entire working range. Based on this, calculate the calibration function for each individual
compound in accordance with ISO 8466-1.
The calibration function is only valid under the spe
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