SIST EN ISO 6468:1998
(Main)Water quality - Determination of certain organochlorine insecticides, polychlorinated biphenyls and chlorobenzenes - Gas chromatographic method after liquid-liquid extraction (ISO 6468:1996)
Water quality - Determination of certain organochlorine insecticides, polychlorinated biphenyls and chlorobenzenes - Gas chromatographic method after liquid-liquid extraction (ISO 6468:1996)
Describes a method for determining certain organochlorine insecticides, polychlorinated biphenyls (PCBs) and chlorobenzenes (except the mono- and dichlorobenzenes) in drinking water, ground water, surface waters and waste waters. The method is applicable to samples containing up to 0,05 g/l of suspended solids.
Wasserbeschaffenheit - Bestimmung bestimmter Organochlorinsektizide, Polychlorbiphenyle und Chlorbenzole - Gaschromatographisches Verfahren nach Flüssig-Flüssig-Extraktion (ISO 6468:1996)
Diese Internationale Norm beschreibt ein Verfahren zur Bestimmung einiger Organochlorinsektizide, Polychlorbiphenyle (PCB) und Chlorbenzole (ausgenommen Mono- und Dichlorbenzole) in Trinkwasser, Grundwasser, Oberflächenwasser und Abwasser. Dieses Verfahren eignet sich für Proben, die bis zu 0,05 g/l suspendierte Stoffe enthalten; in Gegenwart von organischem Material, suspendierten Stoffen und Kolloiden treten häufiger Störungen auf, und die Nachweisgrenzen sind demzufolge höher.
Qualité de l'eau - Dosage de certains insecticides organochlorés des polychlorobiphényles et des chlorobenzenes - Méthode par chromatographie en phase gazeuse apres extraction liquide-liquide (ISO 6468:1996)
La présente Norme internationale décrit une méthode pour le dosage de certains insecticides organochlorés, des polychlorobiphényles (PCB) et des chlorobenzènes (sauf le mono- et le dichlorobenzène) présents dans les eaux destinées à la consommation humaine, les eaux souterraines, les eaux de surface et les eaux usées. La méthode est applicable aux échantillons contenant jusqu'à 0,05 g/l de matières en suspension. En présence de matières organiques, de matières en suspension et de colloïdes, les interférences sont plus nombreuses et les limites de détection sont donc plus élevées. La méthode décrite dans la présente Norme internationale ne donne des informations que sur certains composés PCB spécifiques, et non sur le taux total de tous les composés PCB. Selon les types de composés à détecter et l'origine de l'eau, les limites de détection indiquées au tableau 1 sont applicables pour la méthode décrite dans la présente Norme internationale, pour des eaux à faible teneur organique. Compte tenu des très faibles concentrations habituellement présentes dans les eaux, le problème de la contamination est particulièrement important. Plus le niveau mesuré est faible, plus il faut prendre de précautions et tout particulièrement lorsque les concentrations sont inférieures à 10 ng/l.
Kakovost vode - Določevanje nekaterih organoklornih insekticidov, polikloriranih bifenilov in klorobenzenov - Plinska kromatografska metoda po tekočinski ekstrakciji (ISO 6468:1996)
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST EN ISO 6468:1998
01-januar-1998
.DNRYRVWYRGH'RORþHYDQMHQHNDWHULKRUJDQRNORUQLKLQVHNWLFLGRYSROLNORULUDQLK
ELIHQLORYLQNORUREHQ]HQRY3OLQVNDNURPDWRJUDIVNDPHWRGDSRWHNRþLQVNL
HNVWUDNFLML ,62
Water quality - Determination of certain organochlorine insecticides, polychlorinated
biphenyls and chlorobenzenes - Gas chromatographic method after liquid-liquid
extraction (ISO 6468:1996)
Wasserbeschaffenheit - Bestimmung bestimmter Organochlorinsektizide,
Polychlorbiphenyle und Chlorbenzole - Gaschromatographisches Verfahren nach Flüssig
-Flüssig-Extraktion (ISO 6468:1996)
Qualité de l'eau - Dosage de certains insecticides organochlorés des
polychlorobiphényles et des chlorobenzenes - Méthode par chromatographie en phase
gazeuse apres extraction liquide-liquide (ISO 6468:1996)
Ta slovenski standard je istoveten z: EN ISO 6468:1996
ICS:
13.060.50 3UHLVNDYDYRGHQDNHPLþQH Examination of water for
VQRYL chemical substances
SIST EN ISO 6468:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST EN ISO 6468:1998
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SIST EN ISO 6468:1998
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SIST EN ISO 6468:1998
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SIST EN ISO 6468:1998
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SIST EN ISO 6468:1998
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SIST EN ISO 6468:1998
INTERNATIONAL IS0
STANDARD 6468
First edition
19964245
Water quality - Determination of certain
organochlorine insecticides,
polychlorinated biphenyls and
chlorobenzenes - Gas chromatographic
method after liquid-liquid extraction
Qua/it& de I’eau - Dosage de cetiains insecticides organochlor&, des
polychlorobiph&yles et des chlorobenz&nes - M&hode par
chromatographie en phase gazeuse apr& extraction liquide-liquide
Reference number
IS0 6468: 1996(E)
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SIST EN ISO 6468:1998
ISO6468:1996(E)
Foreword
IS0 (the International Organization for Standardization) is a worldwide fed-
eration of national standards bodies IS0 member bodies). The work of
(
preparing International Standards is normally carried out through IS0
technical committees. Each member t: N )dy 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 collab-
orates closely with the International Electrotechnical Commission (IEC) on
all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are cir-
culated 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 6468 was prepared by Technical Committee
lSO/TC 147, Water quality, Subcommittee SC 2, Physical, chemical, bio-
chemical methods.
Annex A forms an integral part of this International Standard. Annexes B to
H are for information only.
0 IS0 1996
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronic or mechanical, including photocopying and
microfilm, without permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Gen&ve 20 l Switzerland
Printed in Switzerland
ii
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SIST EN ISO 6468:1998
IS0 6468: 1996(E)
INTERNATIONAL STANDARD @ IS0
Water quality - Determination of certain organochlorine
insecticides, polychlorinated biphenyls and chlorobenzenes -
Gas chromatographic method after liquid-liquid extraction
- This method makes use of flammable and toxic organic sol-
WARNING AND SAFETY PRECAUTIONS
vents. Observe the safety regulations in effect.
The electron-capture detector (ECD) contains radionuclides. Adequate safety precautions and legal re-
quirements must be observed.
The halogenated hydrocarbons and chloropesticides, used for the preparation of the calibration standards
are toxic. Therefore, the safety regulations pertaining must be strictly observed.
1 Scope 2 Normative references
The following standards contain provisions which,
This International Standard describes a method for
through reference in this text, constitute provisions of
determining certain organochlorine insecticides, poly-
this International Standard. At the time of publication,
chlorinated biphenyls (PCBs) and chlorobenzenes
the editions indicated were valid. All standards are
(except the mono- and dichlorobenzenes) in drinking
subject to revision, and parties to agreements based
waters, ground waters, surface waters and waste
on the International Standard are encouraged to in-
waters.
vestigate the possibility of applying the most recent
The method is applicable to samples containing up to
editions of the standards indicated below. Members of
0,05 g/l of suspended solids. In the presence of or-
IEC and IS0 maintain registers of currently valid Inter-
ganic matter, suspended matter and colloids, interfer-
national Standards.
ences are more numerous and consequently the
detection limits are higher. IS0 5667-l :1980, Water quality- Sampling - Part 7:
Guidance on the design on sampling programmes.
The method described in this International Standard
only gives information on specific PCB compounds but
IS0 5667-2:1991, Water quality - Sampling - Part 2:
no information on the level of total PCBs.
Guidance on sampling techniques.
According to the types of compounds to be detected
and the source of the water, the detection limits given
in table 1 are applicable for the method described in
3 Principle
this International Standard, with waters of low organic
contents.
Liquid-liquid extraction of organochlorine insecticides,
chlorobenzenes and PCBs by an extraction solvent.
Given the very low concentrations normally present in
After the concentration of the components with low
the waters, the problem of contamination is extremely
volatility and after any clean-up steps which may be
important. The lower the level measured, the more
necessary, the sample extracts are analysed by gas
precautions have to be observed; below concen-
chromatography, using an electron-capture detector.
trations of 10 rig/l,, special care is necessary.
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SIST EN ISO 6468:1998
IS0 6468: 1996(E)
Table 1 - Detection limits
Acronyms Chemical names (IUPAC) Detection limits
Organochlorine insecticides:
HCH 1, 2, 3, 4, 5, 6-hexachlorocyclohexane,
five stereoisomers:
alpha-HCH
beta-HCH
Lindane gamma-HCH
delta-HCH
epsilon-HCH
o,/-DDE I,1 -dichloro-2-(2-chlorophenyl I)-2-(4-chlorophenyl)ethylene
JI,~ ‘-DDE I,1 -dichloro-2,2-bis(4-chlorophenyl)ethylene 1 rig/l
& ‘-DE I,1 -dichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane (= o,/-DDD) to
10 rig/l
/J,JI ’-TDE I,1 -dichloro-2, 2-bis(4-chlorophenyl)ethane (= p,p ’-DDD)
depending
~,JI ’-DDT 1 ,I ,I -trichloro-2-(2-chlorophenyl)-2-(4-chlorophenyl)ethane
~,JI ’-DDT 1 ,I ,I -trichloro-2,2-bis(4-chlorophenyl)ethane on the
Methoxychlor 1 ,I ,I -trichloro-2,2-bis(4-methoxyphenyl)ethane compound
Aldrin (1 R, 4S, 4aS, 5S, 8R, 8aR)-1, 2, 3, 4, 10, IO-hexachloro-1, 4, 4a, 5, 8,
8a-hexahydro-1,4: 5,8-dimethanonaphthalene
Dieldrin (IR, 4S, 4aS, 5R, 6R, 7S, 8S, 8aR)-1,2,3,4,10, IO-hexachloro-1,4,4a, 5,
6,7,8,8a-octahydro-6,7-epoxy-l,4 : 5,8-dimethanonaphthalene
Endrin (1 R, 4S, 4aS, 5S, 6S, 7R, 8R, 8aR)-1,2,3,4,10, IO-hexachloro-l , 4,4a, 5,
6,7,8,8a-octahydro-6,7-epoxy-l,4 : 5,8=dimethanonaphthalene
Heptachlorl) 1,4,5,6,7,8,8-heptachloro-3a, 4,7,7a-tetrahydro-4,7-methanoindenel)
Heptachlor-epoxide 1, 4, 5, 6, 7, 8, 8-heptachloro-2,3-epoxy-3a,4,7,7a-tetrahydro-4,7
-methanoindane
Endosulfanl) *) 1,4,5,6,7,7,7-hexachloro-8,9, IO-trinorborn-5-en-2,3-ylene-dimethyl-
enesulfite:
alpha-Endosulfan
beta-Endosulfan
Chlorobenzenes:
trichlorobenzene 1 rig/l
TrCB
tetrachlorobenzene to
TeCB
PeCB pentachlorobenzene 10 rig/l
HCB hexachlorobenzene depending on
the compound
PCNB (Quintozene) pentachloronitrobenzene
Polychlorinated biphenyls:
PCB 28 2,4,4 ’-trichlorobiphenyl
PCB 52 2,2 ’, 5,5 ’-tetrachlorobiphenyl 1 rig/l
to
PCB 101 2,2 ’, 4,5,5 ’-pentachlorobiphenyl
50 rig/l
PCB 138 2,2 ’, 3,4,4 ’, 5 ’-hexachlorobiphenyl
2,2 ’, 4,4 ’, 5,5 ’-hexachlorobiphenyl depending on
PCB 153
2,2 ’, 3,4,4 ’, 5,5 ’-heptachlorobiphenyl the compound
PCB 180
PCB 194 2,2 ’, 3,3 ’, 4,4 ’, 5,5 ’-octachlorobiphenyl
1) The analysis of a and p - endosulfan as well as heptachlor requires special care due to its low stability.
2) The name “endosulfan” is not acceptable for use in Italy, as it is in conflict with a trade mark registered there.
2
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SIST EN ISO 6468:1998
IS0 6468: 1996(E)
0 IS0
muffle furnace. Cool to about 200 “C in the furnace
Any substance capable of producing a response on
and then to ambient temperature in a desiccator. Store
the electron-capture detector, at a retention time indis-
will in a sealed glass container.
tinguishable from compound of interest,
any
interfere. In practice, many potentially interfering sub-
stances will be removed during the extraction and
4.6 Deactivated alumina.
clean-up procedures.
Weigh a portion of dry alumina (4.5) into a sealable all-
NOTE 1 In general, the use of two capillary columns of
glass container and add 7 % + 0,2 % (m/m) of water
different polarity is sufficient for the organochlorine com-
(4.1). Seal and agitate for at least 2 h to ensure uni-
pounds analysed according to this International Standard.
formity. Store in a sealed glass container.
The results so calculated should be considered as the
maximum concentrations, possibly still influenced by coelut-
ing substances. It is possible that there will be cases where Once the seal has been broken, storage time is nor-
a more definite identification is required. mally about one week. After the maximum storage
time, reprocess batches as described in 4.5 and this
subclause.
4 Reagents and materials
4.7 Alumina/silver nitrate.
All reagents shall be sufficiently pure to not give rise to
significant interfering peaks in the gas chromatograms
Dissolve 0,75 g + 0,Ol g of silver nitrate in 0,75 ml rfI
of the blanks. The purity of reagents used in the pro-
0,Ol ml of water (4.1) using a microburette. Add
cedure shall be checked by blank determinations
4,0 ml +_ 0,2 ml of acetone followed by 10 g + 0,2 g of
. .
(7 6)
deactivated alumina (4.6). Mix thoroughly by shaking
in an open-topped conical flask, protected from light.
NOTE 2 Commercial “pesticide grade” solvents are avail-
Allow the acetone to evaporate at room temperature
able. The use of these products is recommended only after
and prevent condensation, for example by warming
verifying their quality. The quality of a solvent is checked by
with the hand.
evaporation of about 200 ml down to 1 ml and analysis of
the concentrate to determine the compounds subsequently
analysed. The solvent should be considered acceptable if it
Store in the dark and use within 4 h after preparation.
does not give any detectable interfering peaks in the chro-
matogram for the substance of interest.
4.8 Silica gel, of particle size 63 pm to 200 pm,
heated at 500 “C + 30 “C in batches not larger than
4.1 Water purified, for example, using ion-exchange
500 g, for about 14 h. Cool to about 200 “C in the fur-
or carbon-column adsorption.
nace and then to ambient temperature in a sealed
flask which is placed in a desiccator without desiccant.
Use this material within one week. Deactivate the sil-
4.2 Extraction solvent.
ica gel by weighing a suitable quantity of silica and
adding 3 % (m/m) of water (4.1). Agitate for at least 2 h
Hexane, petroleum ether or heptane are suitable.
to ensure uniformity and store in a sealed glass con-
tainer.
NOTE 3 Any other solvents meeting the requirements of
8.3 (recovery rate a 60 Oh) may be used.
The deactivated silica gel shall be used within 24 h.
4.3 Sodium sulfate (NazSO,), anhydrous.
4.9 Toluene.
Heat a portion of about 250 ml to 300 ml of sodium
sulfate powder at 500 “C IfI 20 “C for 4 h + 30 min, cool
4.10 Diethylether, free from peroxides.
to about 200 “C in a muffle furnace and then to ambi-
ent temperature in a desiccator containing magnesium
4.11 Anti-bumping granules, washed with
perchlorate or an equivalent alternative.
acetone.
4.4 Decane (CloH22) or dodecane (C12H2s), or any
4.12 Standard stock solutions.
keeper which is not detected by the electron-capture
detector.
Pure or certified standards of organochlorine insecti-
tides, chlorobenzenes, and PCBs shall be used for
4.5 Dry alumina.
the preparation of standard stock solutions.
Heat a batch of inert alumina, containing particles of
NOTE 4 Suitable solvents for the preparation of standard
size 50 pm to 200 pm and of maximum mass 500 g, at
stock solutions are acetone, pentane, hexane, dimethyl-
500 “C + 20 “C for 4 h + 30 min on a silica dish in a
benzene or isooctane.
3
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SIST EN ISO 6468:1998
@ IS0
IS0 6468: 1996(E)
a length of 25 m to 60 m, coated with stationary
The containers containing the solutions shall be
marked or weighed so that any evaporation losses of phases capable of separating the compounds of inter-
est.
the solvent may be recognized. The solutions shall be
stored in volumetric flasks with ground-glass stoppers
Annex B provides examples of gas chromatographic
at a temperature of 4 ’“C in the dark. Prior to use, they
conditions (tables B.l, B.2 and B.3) and the corre-
shall be brought to ambient temperature and the level
of solvent shall be adjusted, if necessary. sponding gas chromatograms (figures B.1 and B.2).
NOTE 5 A convenient concentration of standard stock sol-
5.3 Separating funnels, of nominal capacities 1 litre
ution is obtained by weighing 50 mg of each determinand
to 5 litres, with a glass tap washed by hexane or a
and dissolving it in 100 ml of the solvent.
polytetrafluoroethylene (PTFE) tap.
The solution is stable for about 1 year.
5.4 High-speed stirrer and magnetic stirring bar,
washed with hexane and coated with polytetrafluoro-
ethylene (PTFE).
4.13 Intermediate standard solutions.
5.5 Microseparator, see example in figure C.I.
Prepare intermediate standard solutions by a suitable
dilution of the stock solution (4.12) with the extraction
solvent (4.2).
5.6 Kuderna-Danish evaporator, see example in
figure D.l.
A typical value is IO pg/ml.
5.7 Snyder microcolumn.
Store the intermediate standard solutions at about
4 “C in the dark. These solutions are stable for six
5.8 Rotary evaporator or any suitable system of
months.
evaporation.
4.14 Working standard solutions.
5.9 Column for drying the extract, filled with 5 g to
7 g of sodium sulfate (4.3) giving a height of about
Prepare at least five different concentrations by suit- 7 cm to IO cm. For example, the dimensions are
able dilutions of the intermediate standard solutions IO mm internal diameter and 250 mm length (see fig-
(4.13) with the extraction solvent (4.2).
ure E.1).
nanograms per mil-
Suitable concentration s are in the
5.10 Column for the alumina-alumina/silver ni-
lilitre range.
trate clean-up, for example, the dimensions are
10 mm internal diameter and 250 mm length (see fig-
Store the solutions at about 4 “C in the dark. These
ure E.1).
solutions are stable for at least one month.
5.11 Macrocolumn for the silica gel clean-up, for
4.15 Cotton wool or glass wool, washed with ex-
example, the dimensions are 19 mm internal diameter’
traction solvent.
and 400 mm length (see figure E.l).
4.16 Water-miscible solvent. 5.12 Microcolumn for the silica gel clean-up, for
the dimensions see figure F.l.
NOTE 6 Acetone, methanol or dimethylformamide may be
used.
5.13 Microlitre syringes.
5 Apparatus 5.14 Miscellaneous glassware.
Laboratory glassware shall be cleaned using a clean-
5.1 Gas chromatograph, with an electron-capture
ing agent (laboratory detergent) followed, for example,
detector (ECD) and suitable for use with capillary col-
by either a treatment with chromium(Vl)/sulfuric acid
umns. This shall be operated in accordance with the
mixture, or peroxodisulfate/sulfuric acid mixture and
manufacturer ’s instructions. On-column or glass-lined
subsequently washed by hexane or heated for at least
injection systems can be used. The oven shall be suit-
12 h at 200 OC, except for the calibrated glassware.
able for isothermal and temperature-programmable
operation.
The efficiency of the treatment shall be experimentally
checked at random by blank determinations to ensure
5.2 Capillary columns, glass or fused-silica capil-
that no interfering contamination has occurred.
laries, with an inside diameter of less than 0,4 mm and
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SIST EN ISO 6468:1998
IS0 6468:1996( E)
@ IS0
Measure the volume of the water to be extracted by
6 Sampling and sample preparation
weighing the bottle before extraction and after empty-
ing.
Take samples according to IS0 5667-l and
IS0 5667-2.
7.2 Extraction and separation
Collect the water samples in brown glass bottles
cleaned as described in 5.14 (do not use plastics bot-
Use either of these two procedures for extraction and
tles) with ground-glass stoppers or with screw caps
separation:
with PTFE liners, of nominal capacity 1 litre to 5 litres.
Fill the bottles to 80 % to 90 %.
- extraction in the sample container and separation
in a separating funnel (7.2.1);
On sample collection, ensure that no interfering sub-
stances enter the water sample, and no losses of the
- extraction in the sample container with a magnetic
determinands occur. This is especially important when
stirrer or a high-speed stirrer and separation by a
using plastics tubing with the sampling apparatus. If
microseparator (7.2.2).
necessary, it shall be proved by control tests that no
losses by adsorption occur. Glass and stainless steel
NOTE 7 Depending on the method used, varying recov-
devices shall preferably be used.
eries and reproducibilities may be obtained. The yields of
the selected method should be checked by the laboratory
Check the pH. If necessary, correct the pH immedi- . .
(8 3)
ately after collection in order to be in the range pH 5 to
7,5.
It is recommended to perform the extraction in the
sample container. Usually, a sample volume of about
If endosulfan is to be determined, take a separate
1 litre is used.
sample and keep it under acidic conditions (pH 2) until
extraction.
7.2.1 Extraction by shaking the sampling bottle
Do not place samples in close proximity to the concen-
and separation in a separating funnel
trated insecticide or PCB or chlorobenzene solutions.
Store in the dark at a temperature of approximately
Add 30 ml of the extraction solvent (4.2) to the sample
4 “C prior to extraction.
(7.1) and shake for at least 10 min.
Ensure that all samples are extracted as soon as
Transfer to a separating funnel of suitable capacity
possible (preferably within 24 h) to avoid decompo-
(5.3) and allow the phases to separate.
sition of the compounds after sampling.
Run the lower aqueous phase back into the sample
Halogenated hydrocarbons of low volatility and or- container. Repeat the extraction twice with 20 ml to
ganochlorine insecticides are relatively stable if trans-
30 ml of the extraction solvent (4.2).
ferred into an organic solvent. Therefore, it is
permissible to store the dried solvent extracts in a re-
Dry the extract using one of the following procedures:
frigerator at 4 “C for up to two months. Evaporation of
- Pass the extract through a drying column (5.9)
the solvent can still occur even under refrigeration.
containing anhydrous sodium sulfate (4.3), pre-
Extracts shall not be allowed to go to dryness and the
viously washed with the solvent (4.2) and collect
volume of solvent shall be restored to the original
the eluate in the evaporating vessel.
amount before starting analysis.
NOTE 8 It is advisable to wash the column with a further
IO ml to 20 ml portion of the solvent (4.2) to obtain a better
recovery. Collect the washings in the evaporating vessel.
7 Procedure
Or
7.1 Sample pretreatment
- Add anhydrous sodium sulfate (4.3) to the flask.
Shake for 1 min. Leave for 5 min and decant the
Sample pretreatment is not normally necessary. extract into the concentration apparatus. The so-
dium sulfate is washed with a further 10 ml to
If the sample container is filled up to the ground-glass 20 ml of solvent (4.2) and the washings added to
joint, shake and pour off 30 ml to 100 ml of the sample the evaporating vessel.
in order to obtain sufficient free volume for the sub-
sequent addition of the solvent. Or
5
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SIST EN ISO 6468:1998
IS0 6468: 1996(E)
@ IS0
- Freeze the extract at - 18 “C for 2 h. The solvent capture detector. 0,l ml of a solution containing 20 g/l of
decane or dodecane in hexane are added to the extract to
extract is decanted from the ice and transferred to
be concentrated.
the evaporating vessel. The ice is washed with a
further 10 ml of solvent (4.2) and the washings
are added to the evaporating vessel.
7.3.2 Concentration using a rotary evaporator
7.2.2 Extraction with a magnetic or a high-speed
Concentrate the extract in a tapered flask, or prefer-
stirrer and separation in a microseparator
ably, in a tapered flask with an ampoule extension on
a rotary evaporator (5.8) to not less than 0,6 ml at a
Add 20 ml to 30 ml of the extraction solvent (4.2) to
constant vacuum of greater than 340 mbar. A
the sample (7.1).
Kuderna-Danish evaporation flask (5.6) is mounted
between the evaporating vessel and the rotary evapo-
With a magnetic stirrer and a stirring bar (5.4), stir for
rator.
at least 10 min, at a speed of at least 1 000 r/min (the
solvent needs to be dispersed finely in the water)
Place the evaporating vessel with the solvent extract
keeping the sample covered, and then allow the
in an unheated water bath or, for higher boiling extrac-
phases to separate. Alternatively, if a high-speed stir-
tants, in a water bath at a temperature not exceeding
rer (5.4) is used, stir for 2 min while keeping the sam-
50 “C. When the concentration is finished, quantitat-
ple covered at a temperature of 4 “C and allow the
ively transfer the extract into a 1 ml measuring flask.
phases to separate.
Carefully rinse the walls of the evaporating vessel with
a small volume of solvent (4.2). Transfer the rinsings
Assemble the microseparator (5.5); pour purified water
to the measuring flask and fill up to volume with the
(4.1) into the funnel until the surface of the organic
solvent.
phase rises sufficiently for the extract to be withdrawn
with a pipette.
Dry the extract as described in 7.2.1.
7.4 Gas chromatography
7.3 Concentration of the extract
For extracts of samples from clean waters, perform
gas chromatographic analysis at this stage without
Concentrate the combined dried extracts from either
further clean-up.
7.2.1 or 7.2.2 by either of the procedures described in
7.3.1 or 7.3.2 or by any other suitable system (5.8).
If the analysis has to be performed with a purification
Ensure that no significant losses of the more volatile
step, proceed to 7.5.
determinands of interest occur.
Set up the gas chromatograph (5.1), fitted with an
7.3.1 Concentration using a Kuderna-Danish
electron-capture detector and equipped with a suitable
evaporator
column (5.2) according to the instructions of the
manufacturer, and ensure it is in a stable condition.
Good detection limits can be obtained by evaporating
the sample extract to a small volume with the
Inject the extract (usually between 1 ~1 and IO ~1 but
Kuderna-Danish evaporator (5.6) and a Snyder micro-
the same volume as that used for calibration) into the
column (5.7) as follows.
gas chromatograph and run a chromatogram.
Collect the dried extract in a Kuderna-Danish evapor-
Compare the gas chromatogram obta ined to t
:hose of
ator.
the standard solut ions (see clause 8).
Add two anti-bumping granules (4.11) and evaporate
Evaluate the gas chromatogram qualitatively and
to 5 ml k 1 ml on a steam bath. Further concentrate
quantitatively (see clause 9).
the extract to less than 1 ml using a Snyder microcol-
umn or a gentle stream of clean inert gas (e.g. nitro-
The requirements applicable to the extent of the
gen) with a tube placed in a warm water bath (not
measurements, and the calibration, evaluation and
exceeding 40 “C).
calculation techniques to be used, are described in
clause 8. The gas chromatogram obtained is checked
NOTE 9 No further precautions are necessary if the ex-
for overlapping occurring at the locations of the reten-
tract is evaporated with this apparatus to a final volume of
tion times of the determinands of interest. If interfering
not less than 0,5 ml. If a smaller final volume is required, it
peaks are present, one of the purification methods de-
is recommended to use a keeper (4.4) in order to avoid
scribed in 7.5 shall be applied. Otherwise, identify and
significant losses. Decane or dodecane may be used as
quantify according to clause 9.
keepers because they are not detected by the electron-
6
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SIST EN ISO 6468:1998
@ IS0 IS0 6468: 1996(E)
alumina. If the alumina/silver nitrate column blackens
7.5 Clean-up and separation
along its entire length, prepare a fresh column (see
7.5.1 .l) and repeat the purification. If total blackening
Applying the procedure described in 7.2 may lead to
is a common occurrence, larger columns may be used
coextraction of relatively polar and/or other undesired
but additional solvent will be required for elution.
substances, which are likely to interfere by the ap-
pearance of unknown peaks overlapping the pesticide
peaks.
7.5.2 Clean-up on silica gel
NOTE 10 Treatment by column chromatography may help
to eliminate some of the substances. However, this method
7.5.2.1 Preparation of the column
cannot be considered as an absolute system.
Use one or both of the following procedures:
Choose a chromatography column (5.12) as shown in
figure F.l in annex F. [Initially without the solvent res-
- clean-up on an alumina-alumina/silve r nitrate col-
ervoir (figure E.2) attached.] Plug the column tempo-
umn, for purification to remove polar compounds
rarily with a rubber cap at the lower end, and fill it with
(7.5.1);
extraction solvent (4.2).
- clean-up on a silica gel column, for separation of
Insert a plug of glass wool (4.15)
close to the
PCB from most insecticides (7.5.2).
end.
NOTE 11 The quality of each batch of columns should be
Suspend 1 g of silica gel (4.8) in the extraction solvent
checked with standard solutions.
(4.2) in a small beaker.
7.5.1 Clean-up on alumina-alumina/silver nitrate
Transfer the suspension to the chromatography col-
column
umn with the aid of a pipette.
Carry out the purification on an alumina-alumina/silver
Let the silica gel settle down during constant vibration
nitrate column as described in 7.5.1 .l and 7.5.1.2. If
of the column, to produce a dense layer. Otherwise,
interference persists, the additional procedure de-
the sodium sulfate which is placed onto the silica gel
scribed in annex A may be carried out.
will move into the silica gel layer.
NOTE 12 Some compounds, for example endosulfan, may
Remove the rubber cap.
be retained on the column.
Carry out the following steps, including the steps de-
7.5.1.1 Preparation of the column
scribed in 7.5.2.2, without interuption as soon as the
column starts dripping continuously.
Place 15 ml + 1 ml of the extraction solvent (4.2) in the
column (5.10), then add 1,O g + 0,2 g of alumina/silver
Place 0,2 g of sodium sulfate (4.3) onto the layer of
nitrate (4.7) and allow to settle while tapping gently.
silica gel. Attach the solvent reservoir to the column
Then add 2,0 g +_ 0,2 g of alumina (4.6) and again al-
and rinse the system with 5 ml of solvent (4.2).
low to settle while tapping gently. Add a sufficient
amount of sodium sulfate (4.3) to produce a 5 mm
Once again, remove the solvent reservoir as soon as
layer on top of the column. Prepare the column im-
the level of solvent has moved down to the column
mediately before use.
section of the apparatus and follow the steps de-
scribed in 7.5.2.2 immediately.
7.5.1.2 Purification
NOTE 13 Alternatively, dry packed and/or commercially
Prepare an alumina-alumina/silver nitrate column as
available disposable columns may be used, if they are
described in 7.5.1.1. Run off the surplus of the extrac-
found to be equally suitable.
tion solvent (4.2). When the solvent level reaches the
top of the column, add the concentrated sample ex-
tract (see 7.3). Wash the sample vessel with
7.5.2.2 Clean-up and separation
2 ml + 0,5 ml of extraction solvent and add the wash-
ings to the column. Elute the column with 30 ml + 1 ml
Add 100 ~1 of the sample extract onto the column with
of extraction solvent. Collect and concentrate the ex-
the aid of a 100 ~1 syringe, just before the meniscus of
tract as described in 7.3 and then perform the gas
the solvent
...
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