SIST EN ISO 10301:1998
(Main)Water quality - Determination of highly volatile halogenated hydrocarbons - Gas-chromatographic methods (ISO 10301:1997)
Water quality - Determination of highly volatile halogenated hydrocarbons - Gas-chromatographic methods (ISO 10301:1997)
Specifies two methods for the determination of highly volatile halogenated hydrocarbons using gas chromatography. Section 2 specifies a method for the determination by liquid/liquid extraction of highly volatile halogenated hydrocarbons in drinking water, ground water, swimming pool water, most rivers and lakes and many sewage and industrial effluents. Section 3 specifies a method for the determination of highly volatile halogenated hydrocarbons in drinking water, surface waters and ground water by a static headspace method. In practise, the head-space method is applicable for industrial effluents as a screening method, but in some cases it is necessary to confirm the result by the liquid-liquid extraction method.
Wasserbeschaffenheit - Bestimmung leichtflüchtiger halogenierter Kohlenwasserstoffe - Gaschromatographische Verfahren (ISO 10301:1997)
Qualité de l'eau - Dosage des hydrocarbures halogénés hautement volatils - Méthodes par chromatographie en phase gazeuse (ISO 10301:1997)
Kakovost vode - Določevanje lahko hlapnih halogeniranih ogljikovodikov - Metoda plinske kromatografije (ISO 10301:1997)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
01-januar-1998
.DNRYRVWYRGH'RORþHYDQMHODKNRKODSQLKKDORJHQLUDQLKRJOMLNRYRGLNRY0HWRGD
SOLQVNHNURPDWRJUDILMH ,62
Water quality - Determination of highly volatile halogenated hydrocarbons - Gas-
chromatographic methods (ISO 10301:1997)
Wasserbeschaffenheit - Bestimmung leichtflüchtiger halogenierter Kohlenwasserstoffe -
Gaschromatographische Verfahren (ISO 10301:1997)
Qualité de l'eau - Dosage des hydrocarbures halogénés hautement volatils - Méthodes
par chromatographie en phase gazeuse (ISO 10301:1997)
Ta slovenski standard je istoveten z: EN ISO 10301:1997
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
INTERNATIONAL IS0
STANDARD 10301
First edition
1997-04-I 5
Water quality -
Determination of highly
volatile halogenated hydrocarbons -
Gas-chromatographic methods
Qualit de I’eau - Dosage des hydrocarbures halog&& hautemen t vola tils -
Mkthodes par chromatographie en phase gazeuse
Reference number
IS0 10301:1997(E)
IS0 10301:1997(E)
Contents
SECTION 1: General
1 .I Scope
1.2 Normative references
1.3 Definition
SECTION 2: Liquid/liquid extraction and analysis by gas chromatography
2.1 Principle
2.2 Interferences
2.3 Reagents
2.4 Apparatus
2.5 Sampling and sample preparation
2.6 Procedure
2.7 Calibration
2.8 Identification and evaluation
2.9 Expression of results
2.10 Precision data
2.11 Test report
0 IS0 1997
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
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microfilm, without permission in writing from the publisher.
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Internet central @I iso.ch
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Printed in Switzerland
ii
IS0 10301:1997(E)
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SECT ‘ION 3: Static headspace method and ana lysis by gas chromatography 22
3.1 Principle
3.2 Interferences 22
3.3 Reagents 22
3.4 Apparatus
3.5 Sampling
3.6 Procedure
3.7 Calibration
3.8 Identification and evaluation 29
3.9 Expression of results 31
3.10 Precision data
3.11 Test report
Annex A (informative) Characteristics of highly volatile halogenated
hydrocarbons
Annex B (informative) Examples of gas chromatograms for highly volatile
halogenated hydrocarbons
Annex C (informative) Example of a microseparator 45
Annex D (informative) Sensitivity of electron-capture detector 46
Annex E (informative) Extraction recovery with pentane
Annex F (informative) Qualitative method for testing the quality of
“penicillin type” stoppers 48
Annex G (informative) Collection of samples
. . .
III
IS0 10301:1997(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide federation of
national standards bodies (IS0 member bodies). The work of preparing International
Standards is normally carried out through IS0 technical committees. Each member
body interested in a subject for which a technical committee has been established has
the right to be represented on that committee. International organizations,
governmental and non-governmental, in liaison with ISO, also take part in the work.
IS0 collaborates closely with the International Electrotechnical Commission (IEC) on
all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for voting. Publication as an International Standard requires
approval by at least 75 % of the member bodies casting a vote.
International Standard IS0 10301 was prepared by Technical Committee lSO/TC 147,
Water quality, Subcommittee SC 2, Physical, chemical and biochemical methods.
Annexes A to G of this International Standard are for information only.
IV
@ IS0 IS0 10301:1997(E)
Introduction
Highly volatile halogenated hydrocarbons are used in industrial, commercial and
domestic fields, and can enter a water body via waste water and may consequ ently
contaminate drinking water. Furthermore, they can originate from the use of chl orine
as an oxidizing agent in water and waste-water treatment. They also can be
introduced by inappropriate handling. In addition, they can be formed by
decomposition of higher molecular mass organohalogen derivatives.
In uncontaminated ground water and rain water, the concentrations of halogenated
hydrocarbons are generally below 0,l ug/l. In surface water they may be higher,
depending on the origin and quality of the water. In untreated waste water the
concentrations may reach saturation of the aqueous phase. In general, the solubility
of these compounds in organic solvents and in fatty material exceeds their solubility
in water.
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INTERNATIONAL STANDARD @ ~so IS0 10301:1997(E)
Water quality - Determination of highly volatile
halogenated hydrocarbons - Gas-chromatographic
methods
Section 1 : General
II . Scope
This International Standard specifies two methods for the determination of highly
volatile halogenated hydrocarbons using gas chromatography.
Section 2 specifies a method for the determination by liquid/liquid extraction of highly
volatile halogenated hydrocarbons in drinking water, ground water, swimming pool
water, most rivers and lakes and many sewage and industrial effluents. Typical values
of “quantification limits” are given in table 1.
Table 1 - Typical values of “quantification limits“ for some highly volatile
halogenated hydrocarbons using liquid/liquid extraction
Compound p!ipxmq
1 Dichloromethane
150 ---1
1 Chloroform I 0,05 - 0,3 I
IO,01 - 0,l
1 Carbon tetrachloride
I
I l,l-Dichloroethane Il,O-5
I
I 1,2-Dichloroethane 15- 10
--I
1 l,l,l-Trichloroethane IO,02 - 0,l
I
I 1,1,2,2-Tetrachloroethane IO,05 - 0,l
I
IO,01 - 0,05
I Hexachloroethane
I
I cis-1,2-Dichloroethylene I5 - 50
~~~ ---I
1 trans-1,2-Dichloroethylene II -10 I
IO,05 - 0,l
I Trichloroethylene
I
I Tetrachloroethylene
IO1 I I
I Hexachlorobutadiene
I WI ---I
I Tribromomethane lo I 1 I
I 1,1,2-Trichlorotrifluoroethane , I
lo1
Section 3 specifies a method for the determination of highly volatile halogenated
hydrocarbons in drinking water, surface waters and ground water by a static head-
space method. Typical values of “quantification limits” are given in table 2.
In practise, the head-space method is applicable for industrial effluents as a screening
method, but in some cases it is necessary to confirm the result by the liquid-liquid
extraction method.
NOTE : When applying this International Standard, the guide on analytical
quality control for water analysis (see lSO/TR 13530) should be followed,
especially for the calibration steps.
IS0 10301:1997(E) 0 IS0
Table 2 - Typical values of “quantification limits” for some highly volatile
halogenated hydrocarbons using static head-space method
1.2 Normative references
The following standards contain provisions which, through reference in this text,
constitute provisions of this International Standard. At the time of publication, the
editions indicated were valid. All standards are subject to revision, and parties to
agreements based on this International Standard are encouraged to investigate the
possibility of applying the most recent editions of the standards indicated below.
Members of IEC and IS0 maintain registers of currently valid International Standards.
IS0 5667-1:1980, Water quality - Sampling - Part 1 : Guidance on the design of
sampling programmes
IS0 5667-2:1991, Water quality - Sampling - Part 2 : Guidance on sampling
techniques
Water quality -
Guide to analytical quality control for water
lSO/rR 13530:-l’
analysis
‘) In preparation.
IS0 10301:1997(E)
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1.3 Definition
For the purposes of this International Standard, the following definition applies :
1.3.1 highly volatile halogenated hydrocarbons: Fluorinated, chlorinated, brominated
and/or iodinated mainly nonaromatic hydrocarbons composed of one to six atoms of
carbon.
NOTE Their boiling points generally fall within the range of 20 “C to 220 “C at atmospheric pressure
(see annex A).
IS0 10301:1997(E)
Section 2 : Liquid/liquid extraction and analysis by gas
chromatography
2.1 Principle
The highly volatile halogenated hydrocarbons are extracted into an organic solvent.
The solution is then analysed by gas chromatography with an electron-capture
detector or any other suitable detector.
2.2 Interferences
Interferences can be due to the sampling procedure, vials and stoppers, solvents,
gases, organic compounds in the laboratory atmosphere and contamination from the
autosampler. Procedures for minimizing contamination are given in 2.5 and 2.6.
2.3 Reagents
All reagents shall be of sufficient purity so as to not give rise to significant interfering
peaks in the gas chromatogram of the solvent extract. The purity of reagents shall be
verified by a suitable procedure, for example, by blank determinations (see 2.6.4).
Reagents can become contaminated by contact with air and other materials,
particularly plastics, or by degradation caused by the action of light. Store all reagents
in the dark in tightly sealed all-glass containers or other suitable vessels.
2.3.1 Water for the preparation of calibration solutions and blank
The quality of the water used shall be determined. For example, use the following
procedure as a suitable preparation method :
Place water in a bottle with a conical shoulder, nominal capacity 2 litres, fitted with a
ground-glass stopper, pretreated according to 2.4.2.
Determine the content of the highly volatile halogenated hydrocarbons in this water.
If the water is contaminated, purify as follows :
- position a glass delivery tube with a sintered glass distributor a few millimetres
above the bottom of the bottle ;
- heat the water to approximately 60 OC ;
- pass a stream of clean nitrogen (approximately 150-200 mI/min) through the
water for 1 h via the bubbler. Let the water cool to room temperature and
stopper the bottle ;
- store the water in a glass bottle in the dark.
@ IS0 IS0 10301:1997(E)
Subsequently verify again the absence of highly volatile halogenated hydrocarbons. If
contamination is found, use a purge gas of another source and repeat the procedure.
2.3.2 Gases for gas chromatography
Nitrogen, ultrapure, volume concentration minimum 99,996 %, or argon-methane
mixture, ultrapure. Other gases for gas chromatography shall be in accordance with
the instrument manufacturer’s instructions.
2.3.3 Extraction solvent (pentane) free from highly volatile chlorinated hydrocarbons
Analyse a sample of the extraction solvent by electron-capture gas chromatography to
ensure that it does not contain material giving rise to interfering peaks in the
chromatogram. If the compound of interest elutes in the same range as the extraction
solvent, then use other solvents such as hexane, petroleum ether, heptane or xylene
(for waste waters), providing that the validity of the result is maintained.
2.3.4 Sodium sulfate, anhydrous
Heat a portion of about 250 g to 300 g of Na,SO, at 500 OC k 20 “C for 4 h it 30 min ;
cool to about 200 “C in a muffle furnace and then to ambient temperature in a
desiccator containing magnesium perchlorate (2.3.6) or equivalent alternative.
2.3.5 Sodium thiosulfate
Prepare a sodium thiosulfate solution (30 g/l) by dissolving 46 g k 0,2 g of sodium
thiosulfate pentahydrate (Na,S,0,m5H,0) in 1 000 ml 2 5 ml water (see 2.3.1).
NOTE : Alternatively, solid sodium thiosulfate may be used.
2.3.6 Magnesium perchlorate
2.3.7 Water-miscible solvent
NOTE : Methanol, acetoneor dimethylformamide may be used.
2.3.8 Reference substances
Pure examples of the highly halogenated hydrocarbons to be determined are
required.
Store these reference substances in areas separate from sample extracts and the
solvent used for the extraction.
ambient temperature, it is recommended to use
which are gaseous at
NOTE : For reference substances
solutions.
commercially available
0 IS0
IS0 10301:1997(E)
2.3.9 Standard stock solutions
Prepare standard stock solutions by adding with a microlitre syringe defined
quantities of each reference substance (see 2.3.8) under the surface of a suitable
solvent.
NOTE Suitable solvents for the preparati on of standard stock solutions are acetone, pentane, hexane,
dimethylbenzen e or is0 Ioctane.
The containers containing the solutions shall be marked or weighed so that any
evaporation losses of the solvent may be recognized. The solutions shall be stored in
volumetric flasks with ground glass stoppers at a temperature of 4 “C in the dark.
Prior to use, they shall be brought to ambient temperature and the level of solvent
shall be adjusted, if necessary.
NOTE 1: A convenient concentration of standard stock solution is obtained by weighing 50 mg of the
reference substance and dissolving it in 100 ml of the solvent. The solution is stable for about
1 year.
NOTE 2: For practical reasons, it is recommended to use mixed standard stock solutions.
2.3.10 Intermediate standard solutions
Prepare intermediate standard solutions by a suitable dilution of the stock
solution (see 2.3.9) with the extraction solvent (see 2.3.3).
A typical value is 10 ug/ml.
Store the intermediate standard solutions at about 4 “C in the dark. These solutions
are stable for 6 months.
2.3.11 Working standard solutions
Prepare at least five different concentrations by suitable dilutions of the intermediate
standard solutions (see 2.3.10) with the extraction solvent (see 2.3.3).
Suitable concentrations are in the ng/ml range. Store these solutions at about 4 “C in
the dark. These solutions are stable for at least 1 month.
2.4 Apparatus
2.4.1 Gas chromatograph fitted with an electron-capture detector or any other suitable
detector and with suitable columns.
Separation of the highly volatile halogenated hydrocarbons requires high separation
power. The best separations are obtained with capillary columns.
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IS0 10301 :1997(E)
Different reference columns (specific for volatiles compounds) are available from the
chromatographic equipment suppliers. The choice depends on the variety of
substances to be analysed, the sampling technique, gas chromatograph configuration,
etc.
As a guide, the following rules may be applied to the gas chromatograph column:
a) nonpolar
[(poly(dimethylsiIoxane)] or semipolar [(poly(5 %-diphenyl-95 %
dimethylsiloxane)] bonded phases ;
b) as the relation between internal diameter and film thickness is a critical parameter,
choose a phase ratio around 80 - 100 (suitable for volatile, low molecular
mass compounds) ;
c) length : generally, more than 30 m.
Annex B gives several examples of separation.
NOTE : N onvolatile compoun ds, contain ed for example in water, may shorten the lifetime of the
gas chromatograph ic column.
2.4.2 Ordinary laboratory glassware
As an example of preparation, glassware to be used may be washed with detergent,
rinsed with deionized water and finally with the extraction solvent or heated in an
oven at 150 OC for at least 1 h and cooled at room temperature before use.
In order to minimize contamination during transport or storag
e, close the vessels and
protect the neck of the bottle, for example with aluminium foil.
All syringes shall be thoroughly cleaned and their clean liness verified by gas
chromatography before use.
2.4.3 Glass bottles, capacity about 250 ml, sealed with a solid glass stopper.
Prior to use, place the bottles upside down in a ventilated drying oven along with the
stoppers and heat them for at least 1 h at 150 OC.
2.4.4 Glass vials of capacity approximately 30 ml to 40 ml,
with
polytetrafluoroethylene (PTFE) coated septum.
2.4.5 Magnetic stirrer or mechanical shaker
2.4.6 Magnetic stirrer rods (length approximately 4 cm), coated with PTFE. Store the
magnetic stirrer rods separately for each concentration range.
IS0 10301 :1997(E)
2.4.7 Microseparator (see as an example annex C, figure C.l).
2.4.8 Glass wool washed with extraction solvent.
2.4.9 Bottles with PTFE-coated septum, capacity approximately 2 ml, to store the
extract.
2.5 Sampling and sample preparation
Take samples according to IS0 5667-l and IS0 5667-2.
Collect and store the water samples in bottles (see 2.4.3) cleaned as described in 2.4.2.
In the special case of septum-vial extraction (see 2.6.2), fill glass vials (see 2.4.4).
Collect the sample normally by immersion, by filling the bottle or the vial completely,
discarding this water, refilling and stoppering so as to leave no headspace.
Loss of volatile compounds through degassing of the sample shall be avoided. Slowly
fill the bottle at the sampling point until it overflows, avoiding turbulence.
The use of plastics tubing when taking samples shall be kept to a minimum in order to
avoid losses or contamination of the sample.
If reaction between free halogens and organic matter in the sample, to produce
trihalogenated methanes, is to be eliminated, add an excess of sodium
thiosulfate (see 2.3.5) to the sampling bottle or vial after rinsing the bottle or the vial
but prior to sampling.
NOTE : The quantity of sodium thiosulfate added to the sample is not critical but should be sufficient to
react with all the chlorine present. Normally 0,l ml to 0,2 ml of a 30 g/l solution (see 2.3.5) or a
few crystals (3 mg to 5 mg) of solid sodium thiosulfate will be appropriate for a sample volume
of about 250 ml.
If an internal standard is needed, it shall be added as soon as possible after sampling.
Avoid warming the sample during the transport.
If storage is unavoidable, cool the samples to about 4 “C and carry out the extraction
within 48 h, if possible, since the extracts are much more stable than the water
samples.
NOTE : If composite samples are being analysed, losses of highly volatile chlorinated hydrocarbons may
occur when individual samples are mixed.Therefore, individual samples should be extracted
separately and the solvent extracts combined before analysis.
2.6 Procedure
Use the extraction procedures described in 2.6.1 or 2.6.2. If in the laboratory,
contamination of the sample by air cannot be excluded, use septum-vial
extraction (see 2.6.2).
IS0 10301: 1997(E)
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2.6.1 Extraction
Take the full sample bottle (see 2.5) and discard enough water so that there is a
residual sample volume of 200 ml f: 10 ml. Weigh the bottle and sample in order to
accurately determine the sample volume. Add the extraction solvent (see 2.3.3), close
and mix vigorously with the sample using a magnetic stirrer or a mechanical shaker
for 5 min (see 2.4.5), to ensure that the extractant is finely dispersed in the sample in
order to obtain a reproducible recovery.
NOTE : The volu the type of sample ; suitable vol umes are 10 ml for
me of solve nt used depends upon
drinkin
g water and 50 ml for waste water.
After mixing, allow the sample container to stand until the layers separate. Draw ofi
directly the upper solvent layer using a pipette or, if the phases are not well
separated, a microseparator (see 2.4.7) as follows :
Insert a glass wool plug (about 2 cm) through the central tube of the microseparator
until it reaches the wider part. Rinse the tube and the plug with extraction solvent and
dry both. Place the microseparator on top of the bottle containing the extracted
sample and slowly add through the side tube sufficient water (see 2.3.1) so that the
extract rises in the central tube past the glass wool.
It is not necessary to filter all of the organic phase through glass wool to obtain
sufficient liquid for analysis.
If this treatment is not successful, separate the phases by centrifugation of a few
millilitres of the turbid organic phase in a closed glass vessel (such as a centrifuge
tube with a screw cap) or by freezing.
Do not concentrate the sample extract by evaporation.
Immediately proceed to gas chromatographic analysis (see 2.6.3). If analysis cannot
be carried out immediately, store the solvent extract in an airtight stoppered
bottle (see 2.4.9) at a temperature of about 4 “C, no longer than one month.-
NOTE : For higher-boiling extraction solvents, such as hexane or 1,2-dimethylbenzene (o-xylene), cooling
is not necessary; 1,2-dimethylbenzene extracts should be dried with anhydrous sodium
sulfate (see 2.3.4) or magnesium perchlorate (see 23.6) (approximately 10 mg/ml) prior to gas
chromatographic analysis.
The extraction shall be carried out in an environment as free as possible from volatile
halogenated compounds. Often, interfering peaks will occur, especially at the
beginning of the chromatogram. Contamination of the sample may be caused by
sprays being used, solvents in the laboratory or refrigerants coming from chillers,
Blank determinations (see 2.6.4) are necessary.
2.6.2 Septum-vial extraction
NOTE : Owing to the absence of a headspace, mixing with this technique is less efficient than using a
bottle as in 2.6.1. Recoveries may be a little lower but are acceptable and reproducible.
IS0 10301:1997(E) @ IS0
Take the vial (see 2.4.4) filled according to 2.5 and insert a hypodermic syringe needle,
through the septum, a distance of approximately 1 cm into the sample. Fill a 5 ml
syringe with extraction solvent (see 2.3.3) and adjust the volume in the syringe
to 2,5 ml, taking care to exclude any air bubbles. Insert the syringe needle, with
syringe containing solvent now attached, through the septum, as far as possible into
the vial. Invert the syringe plus vial (vial now above syringe) and inject the 2,5 ml of
extraction solvent (see 2.3.3) into the vial. 2,5 ml of sample will be displaced via the
open syringe needle. Withdraw both needles and shake the vial vigorously for 5 min.
Allow the layers to separate.
Then proceed to gas chromatographic analysis (see 2.6.3) or keep the extract with the
water present for analysis. These extracts have proved stable for one month when
stored in the vials, in the dark, at a temperature of about 4 “C.
he vo lume of the v ial s being reproduc ible. Nevertheless each vial should
NOTE : This method relies on t
llume noted for use in recovery checks.
be checked and its vo
2.6.3 Gas chromatography
Set up the gas chromatograph (see 2.4.1), fitted with an electron-capture detector or
any other suitable detector and equipped with a suitable column, according to the
manufacturer‘s instructions.
Normally, better resolution will be obtained with capillary columns.
The electron-capture detector is sensitive to halogenated hydrocarbons, but is not
specific in its response. Its sensitivity to different halogenated hydrocarbons varies
considerably (see annex D, table D.1) and the linearity of response to the compounds
of interest and the useable working range of concentrations shall be determined by
investigation using a series of calibration standard solutions of known concentrations.
Eliminate any contamination of the electron-capture detector which may cause a high
or unsteady baseline according to the instructions of the manufacturer. Such
contamination may be caused by contaminated gas (especially oxygen
contamination) or a dirty detector due to a high column bleeding rate.
Should it be found necessary to clean the detector, the detector response and linearity
shall be reconfirmed after cleaning and before further samples are analysed.
Inject an aliquot of the clear extract (see 2.6.1) into the injection port of the gas
chromatograph or, in case of septum-vial extraction (see 2.6.2), withdraw aliquots of
the solvent layer for gas chromatographic analysis through the septum using an
appropriate microsyringe.
Compare the gas chromatogram obtained to those of the standard solutions (see 2.7).
Evaluate the gas chromatogram qualitatively and quantitatively (see 2.8). The
requirements concerning the measurements, the calibration, evaluation and
calculation techniques to be used are described in 2.7 and 2.8.
ISO10301:1997(E)
@ IS0
2.6.4 Blank determination
Prior to analysis and at regular intervals, carry out full blank determinations using
water (see 2.3.1).
Take the blank through the complete analytical procedure, starting with sampling and
including all steps until the evaluation of the gas chromatogram.
If the blank value is too high (> 10 % of the measured value for any of the compounds
of interest), find the cause through step-by-step examination of the procedure.
Decrease the blank value through suitable measures (for example, extraction of the
“clean water” with the extraction solvent prior to analysis, elimination of
contamination in the room air, checking of the gas chromatograph and integration
parameters).
In the case of high blank values caused by laboratory air contamination, follow the
method given in 2.6.2.
2.7 Calibration
Initially, determine the recovery ; obtain this recovery with the two following
calibration steps :
a) calibration by direct injection of solvent standard solutions (see 2.7.1).
This gives information on the linear working range of the detector, retention
times and relative responses of the determinands.
b) calibration of the overall procedure (see 2.7.2) using spiked water samples, and
extraction.
The data obtained from 2.7 a) are compared with those from 2.7 b) in order to
calculate the recovery (see 2.7.3) of each determinand.
Carry out the daily recalibration (see 2.7.4) with solvent standard solutions according
to a) or with spiked water extracts according to b).
The use of an internal standard is recommended (see 3.7.3.2) ; it allows some
correction of differing extraction recovery and errors in the injected volume, for
example :
- I-bromo-2-dichloroethane ;
- 1,2-di bromoethane ;
- ~KUE-I ,2-dichloroethylene ;
- bromotrichloromethane ;
- 1,2-dibromo-l,l-dichloroethane.
IS0 10301:1997(E) @ IS0
Tab I e 3 gives an explanation of the subscripts used in equations and the following
text .
Table 3
- Explanation of the subscripts used in the symbols
Index Meaning
i Identity of the determinand
e Measured value in calibration
Entire procedure
g
Internal standard
I
2.7.1 Calibration with an external standard, not using the overall procedure
Inject defined volumes in the range of 1 ul to 5 ul of the working standard
solutions (see 2.3.11) into the gas chromatograph.
Measure the gas chromatograph signals for each substance (peak heights or peak
areas or integration units respectively) and calculate concentrations.
For a graphic presentation of the calibration curve, plot the respective measured value
yie on the ordinate against the respective mass concentrations pi, of the substance i on
the abscissa.
The injection volume used for calibration and for the measurement of the sample
solutions shall be kept constant.
The series of measured values thus obtained shall be used to establish the linear
regression function as follows :
= mi l pie + bi
(1)
Y
ie
where :
is the (dependent variable) measured response of substance i, depending
Y
ie
. the units depend on the evaluation, for example, area value ;
On Pie f
is the (independent variable) mass concentration of the substance i
P
ie
(external standard) in the calibration solution, in micrograms per litre ;
is the slope of the calibration curve of substance i ; (corresponds to the
mi
substance-specific response factor 5) The units depend on the evaluation,
for example, area value x (l&g) ;
is the intercept of the calibration curve on the ordinate ; the unit depends
b
i
on the evaluation for exemple, area value. As a rule, the intercept is very
small. If it is large, the gas chromatographic system and the evaluation
system shall be checked.
@ IS0 IS0 10301:1997(E)
2.7.2 Calibration of the overall procedure using external standard
For each compound a separate calibration function (via the overall procedure) shall be
established, consisting of at least five measurement points. It is permissible to
examine several compounds in one calibration experiment.
To calibrate the entire procedure, prepare aqueous solutions by spiking
water (see 2.3.1) with the compounds to be determined in an individual concentration
range within the linear dynamic range of the detector as follows :
2.7.2.1 Preparation of spiked aqueous standard solutions
To a 100 ml volumetric flask, containing about 90 ml of water-miscible
solvent (see 2.3.7), add, under the surface of the solvent using a microlitre
syringe (see 2.4.2), known quantities of the standard stock solutions (see 2.3.9) of each
determinand. Immediately make up to volume with the water-miscible
solvent (see 2.3.7).
Stopper the flask with a ground-glass stopper and cautiously shake the solution.
Calculate the respective concentration of each substance added.
The solution prepared in this way can be stored at a temperature of about 4 “C in the
dark for several weeks. Prior to use, equilibrate at room temperature for at
least 15 min.
Prepare at least 5 spiked aqueous standard solutions covering (depending on the
compounds) the range 1 ug/l to 200 ug/l by adding different volumes of the above
solution to water (see 2.3.1).
For the blank measurement, add to one bottle of water (see 2.3.1) the same quantity
of solvent used for the preparation of the spiked aqueous standard solutions.
Use quantities such that the volume added is as small as possible (s 1 ml/l of water),
in order to minimize any effect on the partition equilibrium.
Prepare the spiked aqueous standard solutions on the day of use.
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2.7.2.2 Calibration curve
Extract these spiked aqueous standard solutions (see 2.7=2J) as described in 2.6.1
or 2.6.2.
The ratio of the volume of aqueous solutions to the volume of extraction solvent shall
be identical to that of the flasks containing the samples.
Inject into the gas chromatograph the extract of the blank solution and then the
calibration solutions with concentrations Pieg in ascending order. Measure the peak
values ~~~ of the the calibration samples.
Calculate a regression function for each substance using the pairs of values Yieg
Deduct the value of the appropriate blank from each measured value ~~~~
and Pieg’
(2)
Y
ieg = mig ’ Pieg + big
where :
is the (dependent variable) measured response of the substance i during
Y
ieg
calibration, depending on Pieg’ The units depend on the evaluation, for
example area values ;
is the (independent variable) mass concentration of the substance i in the
P
ieg
calibration solution (external standard), in micrograms per litre ;
is the slope of the calibration curve of substance i ; corresponds to the
mig
substance-specific response factor, often referred to as {. The units depend
on the evaluation, for example, area values x (l/ug) ;
b is the axis intercept of the calibration curve on the ordinate. The units
ig
depend on the evaluation, for example, area values.
Plot the reference functions with the ordinate as the substance-specific measured
signals ~~~ and the abscissa as the mass concentration Pieg of the substance i in the
spiked aqueous calibration solution. With the aid of the calibration curve, define the
working range of the procedure.
2.7.3 Determination of the recovery
Determine by means of the calibration procedure according to 2.7.1 and 2.7.2 the
substance-specific mean recovery Ai, for the substance i [see equation (3)].
mig
-
.-
A
(3)
I
hi/F,)
@ IS0 IS0 10301:1997(E)
where :
A is the mean recovery for the substance i ; dimensionless ;
i
see equation (1) ;
mi
see equation (2) ;
mig
F lvent
is the volume ratio of extraction so to sample. This factor has to be
V
le vo
calculated taking into account samp lume, extractant volume, dilution
factors (if applicable).
The following equation applies :
V
E
=-
F
(4)
v
V
P
where :
is the final extraction solvent volume, in millilitres ;
V
E
v is the sample volume, in millilitres.
P
The recovery thus obtained is valid only under the experimental conditions used.
A high recovery is an essential prerequisite for good precision and accuracy of the
analytical result. Variations of these values will indicate problems in extraction and
preparation of standards. The recovery depends on determinands and is generally
greater than 60 %. If not, the procedure should be checked.
Annex E (see table E.l) gives examples showing typical recovery data for drinking
water.
2.7.4 Recalibration
For routine recalibration of the method, it is essential to work within the previously
established linear range (see 2.7.1 or 2.7.2). This shall be updated regularly, especially
when contaminated samples such as sewage or industrial effluents are analysed, as
these may affect the detector and hence the linear range.
The minimum requirement for daily recalibration shall be injections of two standard
solvent solutions (see 2.3.11) or two spiked water extracts (see 2.7.2). The
concentration of the first solution shall be about 20 % of the selected linear working
range, the concentration of the second solution about 80 %.
Calculate a regression function.
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IS0 10301: 1997(E)
Compare this function to the previous established calibration curve (see 2.7.1
or 2.7.2). If the values are within the range of the confidante limits of the previously
established calibration curve (see 2.7.1 or 2.7.2)’ use the new calibration for
evaluation. If not, check the system and establish a complete new calibration curve.
2.8 Identification and evaluation
2.8.1 Identification of individual compounds
If, in the chromatogram of the sample extract run on a particular capillary column, no
peak appears at the substance-specific retention time, consider the compound as not
being detected.
If a peak appears at a particular substance-specific retention time, the presence of the
compound is possible. Confirm the identity of this compound:
Repeat the complete comparison procedure, using a capillary column with a different
polarity.
Normally, the reliability of the identification increases with increasing difference in the
polarities of the column applied. If the comparative study with two capillary columns
of differing polarities reveals the presence of peaks at the expected substance-specific
retention times, consider the identity of the substance as highly probable.
NOTE : If necessary, mass spectrometry can be used for further confirmation.
2.8.2 Evaluation of individual compounds
2.8.2.1 Evaluation using (re)calibration according to 2.7.1
Calculate the mass concentration pi of the substance i in the water sample, using
equation (5) after solving equation (1) for the mass concentration pi :
Yisbi
--
.-
(5)
P
I
mi
where :
is the mass concentration of the substance i in the water sample
P
i
(uncorrected by recovery), units ug/l ;
is the measured value of the substance i in the extract of the water sample
Y
i
(on condition that the same procedure is applied as with the calibration and
units depend on the evaluation, for example,
the sample measurement) ;
area values ;
is the slope of the calibration curve (see 2.7.1 or 2.7.4) of the substance i ;
mi
units depend on the evaluation, for example, area value x (l/ug) ;
@ IS0 IS0 1’0301 :1997(E)
is the axis intercept of the reference line on the ordinate ; units depend on
b
i
the evaluation, for example, area values.
If data taking into account recovery are required, the mass concentration pi, of the
substance i is calculated using equation (6) after solving equation (1) for the mass
concentration pi, :
K -bi
=-
(6)
P ic
mi Ai
where :
is the mass concentration of the substance i in the water sample (corrected
P
ic
by mean recovery), units ug/l ;
is the measured value of the substance i in the extract of the water sample
Y
i
(on condition that the same procedure is applied as with the calibration and
the sample measurement) ; units depend on the evaluation, for sample,
area values ;
is the slope of the calibration curve (see 2.7.1 or 2.7.4) of the substance i ;
mi
units depend on the evaluation, for example, area value x (l&g) ;
is the axis intercept of the reference line on the ordinate ; units depend on
b
i
the evaluation, for example, area values ;
is the specific mean recovery for the substance i.
A
i
2.8.2.2 Evaluation using (re)calibration according to 2.7.2
Calculate the mass concentration pi,
of the substance i in the water sample using
equation (7) after solving equation (2) for the mass concentration pi, :
b
Y
ig -
ig
-
(7)
_ _
P ig-
mig
where :
is the mass concentration of the substance i in the water sample (corrected
P
ig
by recovery), units ug/l ;
is the measured value of the substance i in the extract of the water sample
Y
ig
(on condition that the same procedure is applied as with the calibration and
units depend on the evaluation, for example,
the sample measurement) ;
area values ;
is the slope of the calibration curve (see 2.72 or 2.7.4) of the substance i ;
mig
units depend on the evaluation, for example area values x (l&g) ;
IS01 0301:1997(E) @ IS0
b is the axis intercept of the reference line on the ordinate ; units depend on
the evaluation, for example area values.
2.8.3 Summary of the results
When the procedure described is applied, gas chromatography provides one
individual result for each column used. Derive the final quantitative result from these
two individual results as follows :
a) take the arithmetic mean, provided the differences between the individual results
are less than 10 %, related to the lower result ;
b) choose the smaller value in the event of larger differences, provided that the
smaller value is not caused by leakage in the gas chromatograph system. The
larger value may be the result of peak overlap. Such a result shall be reported as
a measured value, obtained from a single separation only.
2.9 Expression of results
Report the results, in micrograms per litre, to not more than two significant digits, as
follows :
- at mass concentrations < 10 ug/l, report to the nearest Of1 ug/l ;
- at mass concentrations 3 10 ug/l, report to the nearest I pg/l.
EXAMPLES :
- trichloroethylene
0’8 I-@ ;
- tetrachloroethylene 110 ug/l.
@ IS0 IS0 10301:1997(E)
2.10 Precision data
Data of interlaboratory tests are given in tables 4, 5 and 6.
Table 4
- Standard deviations of tap water
b) High spike
a) Low spike
Compound Spike Mean Standard Recovery Spike Mean Standard Recovery
level cont. deviation % level cont. deviation %
found % found %
w/l
w/l
20,o 18,4 3,7 92,2
2,09 73 105
l,l-Dichloroethylene 2,00
91 5,O 4,72 2,3
0,500 0,453 9,l
l,l,l-Trichloroethane
100,o 4,2 77
8,18 3,5 82 72,2
1,1,2-Trichloroethane IO,00
120 5,O 5,26 3,4
0,500 0,600 II,2
Tetrachloroethylene
2,2
5,O 4,85 97
0,385 7,2 77
1,1,1,2-Tetrachloroethane 0,500
84 20,o 17,l 44
2,00 I,68 6,4
1,1,2,2 Tetrachloroethane
2,5 2,53 3,2 101
0,200 8,8 80
Carbon tetrachloride 0,250
86 25,0 98
2,50 2,15 6,2 19,5 4,9
Chloroform
4,89 4,2 78
IO,4 96 5,O
Trichloroethylene 0,500 0,479
25,0 84
2,50 I,85 9,8 74 21,l 3,4
Bromodichloromethane
2,50 I,80 6,2 72 3,7 89
Dibromochloromethane 25,0 22,3
IO,5 90
Bromoform 2,50 2,26 25,0 22,2 5,l 89
0,500 0,215 47,6 42 4,47 3,8 89
Pentachloroethane 5,O
NOTES
These data are taken from “Determination of very low concentrations of hydrocarbons and halogenated
hydrocarbons in water, 1984-5, Table 6”, in the series: Methods for the Examination of Waters and Associated
Materials, Her Majesty’s Stationery Office.
2 Extraction conditions : IO ml petroleum ether per 200 ml sample, extraction in separatory funnel, shaking for
5 min by hand.
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Table 5 - Precision data for drinking water
Parameter I n X x R
(7r “‘r uR “CR
“a ref
pg/l %
% l-q/l % pg/l %
l-al
16,l 110 I,6 9’9 2,99 18,6
Trichloromethane 18 70 0 14,7
Tetrachloromethane 18 70 0 15,9 16,8 106 LO 12,0 4,8 28,6
0,96 7,0 z1 14,9
l,l,l - trichloroethane 17 63 IO 13,l 13,7 105
16 60 14 14,6 15,2 104 1'0 68 216 17,0
Trichloroethylene
7,7 3,l 19,l
Tetrachloroethylene 17 65 7 16,l 15,9 99 12
17 65 7 14,3 13,2 92 12 817 22 16,3
Tribromomethane
I is the number of laboratories R is the percentage recovery
is the repeatability standard deviation
n is the number of values
cTr
is the percentage of outliers
is the repeatability variation coefficient
“a
vcr
is the reference concentration
X
is the reproducibility standard deviation
ref
uR
is the total mean concentration
x is the reproducibility variation coefficient
“CR
NOTES
1 Interlaboratory test carried out in Germany in 1986.
2 Extraction solvent used : pentane. The performance data are generated using the calibration according to
2.7.2 and by a phase-volume ratio with the extraction of 50 : 1. Therefore in some cases the extracts had to be
diluted for final measurement. All participants received the same standard stock solution.
IS0 10301:1997(E)
@ IS0
Table 6 - Precision data for waste water
Parameter I n X x R
ur
“a ref vcr uR “CR
0 / LJg/l pg/l % pg/l % jJg/l %
4,2 513 18.7 23,6
18 70 0 - 79,2 -
Trichloromethane
Tetrachloromethane 1 18 I762 t 96 I 23.9
I 70 IO I 793 172 f I94 I 1 18,3
1,l.l Trichloroethane I 18 lo 1 657 1712 1108 , 189 I 1 12,3 1 17.2
I 70 163
117 I 74,7 1102 , 1 19.8
Trichloroethvlene I 66 16 I 73,o 173 197 f 1 14,8
14,7 18,l
80,5 81,3 101 614 7,8
Tetrachloroethylene 18 70 0
101 153 46.2
9 33 13 65,8 II,9 II,8 46,5
Dichloromethane
I is the number of laboratories R is the percentage recovery
n is the number of values is the repeatability standard deviation
gr
is the percentage of outl
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