ISO 15680:2003

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 2003
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©  ISO 2003
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ii © ISO 2003 — All rights reserved

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

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.
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

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
...