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STANDARD
First edition
1992-I 2-15
Animal and vegetable fats and oils -
Determination of residual technical hexane
content
Corps gras d’origines animale et kg&ale - Dosage de I’hexane
technique r&duel
Reference number
IS0 9832:1992(E)
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IS0 9832: 1992(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 9832 was prepared by Technical Committee
ISO/TC 34, Agricultural food products, Sub-Committee SC 11, Animal and
vegetable fats and oils.
0 IS0 1992
All rights reserved. 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 per-
mission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-1211 Geneve 20 l Switzerland
Printed in Switzerland
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INTERNATIONAL STANDARD
IS0 9832:1992(E)
Animal and vegetable fats and oils - Determination
of residual technical hexane content
4 Principle
1 Scope
Desorption of volatile hydrocarbons by heating at
This International Standard specifies a method for the
80 “C in a closed vessel after addition of an internal
determination of the residual technical hexane con-
standard. Determination of the particular volatile
tent of animal and vegetable fats and oils (referred to
hydrocarbons content of the headspace by gas chro-
as fats hereinafter).
matography using packed or capillary columns.
The method is suitable for the determination of
hexane contents between 10 mg and 1 500 mg per
5 Reagents
kilogram of fat.
All reagents shall be of recognized analytical grade
The method is not applicable to marine oils.
unless otherwise stated.
5.1 Technical hexane, with a composition similar to
2 Normative reference
that of hexane used in industrial processing, or, if this
is not available, n-hexane.
The following standard contains provisions which,
through reference in this text, constitute provisions
NOTE 1 It is recommended that technical hexane be
of this International Standard. At the time of publi-
used for the calibration. This reagent usually has an
cation, the edition indicated was valid. All standards
n-hexane content of 50 % (m/m) and consists mainly of C,
are subject to revision, and parties to agreements isomers but may include C, and C, hydrocarbons.
based on this International Standard are encouraged
to investigate the possibility of applying the most re-
5.2 Internal standard, n-heptane.
cent edition of the standard indicated below. Mem-
bers of IEC and IS0 maintain registers of currently
If this is not available, cyclohexane may be used,
valid International Standards.
provided that the solvent (5.1) used for the extraction
or calibration has a negligible content of cyclohexane
IS0 661: 1989, Animal and vegetable fats and oils -
and/or n-heptane or components with similar re-
Preparation of test sample.
tention times.
5.3 Carrier gas, e.g. hydrogen, nitrogen or helium,
etc., thoroughly dried and with an oxygen content of
3 Definition
less than 10 mg/kg.
For the purposes of this International Standard, the
5.4 Auxiliary gases, hydrogen (99,9 % pure, free
foilowing definition applies.
from organic impurities) and air (free from organic
impurities).
3.1 residual technical hexane content: Content of
volatile hydrocarbons such as those remaining in fats
5.5 Calibration fat, freshly refined and deodorized
following processing involving the use of hydrocarbon
vegetable fat, the technical hexane content of which
solvents, when determined by the method specified
is negligible.
in this International Standard.
The content is expressed as milligrams of hexane per NOTE 2 This material should be free from peroxides or
other components likely to decompose with the formation
kilogram of sample.
1
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IS0 9832:1992(E)
of volatile material which could be confused with hydro- pering bath has been shown to be satisfactory. In this case,
carbons during the test. manual injection is not necessary.
6.8 Heating bath, equipped with clamps for hoiding
6 Apparatus
septum vials, regulated thermostatically at
80 “C + 2 “C.
Usual laboratory equipment and, in particular, the fol- -
lowing.
NOTE 4 For continuous operation, glycerol is rec-
ommended as the heating medium.
6.1 Septum vials, of 20 ml capacity.
6.9 Shaking machine
6.2 Septa, inert to fats and solvents, made of a
material such as butyl rubber or red rubber free from
hydrocarbon solvent residues, and of a suitable quality
7 Sampling
that they will not swell under the conditions of use,
aluminium caps suitable for use with the vials (6.1)
It is important that the laboratory receive a sample
and crimping pliers.
which is truly representative and has not been dam-
aged or changed during transport and storage.
6.3 Tongs, suitable for holding the vials (6.1).
Sampling is not part of the method specified in this
International Standard. A recommended sampling
6.4 Syringes, of 10 ~1 capacity, used only for
the
method is given in IS0 5555.*)
analysis of residual technical hexane. They shall not
be cleaned with hydrocarbon solvent.
It is essential that the sample be protected from gain
or loss of solvent residues.
6.5 Syringes, of 1 J.LI capacity, used only for the
analysis of residual technical hexane. They shall not
be cleaned with hydrocarbon solvent.
8 Preparation of test sample
Prepare the test sample in accordance with IS0 661,
6.6 Syringes, of 1 000 JLI capacity, gas-tight, used
taking care to prevent gain or loss of solvent.
only for the analysis of residual technical hexane. They
shall not be cleaned with hydrocarbon solvent.
9 Procedure
6.7 Gas chromatograph, with a flame ionization
detector and an integrator and/or recorder, equipped
with either
9.1 Calibration
a packed glass column, 2 m to 4 m long and of
a)
9.1.1 Weigh, to the nearest 0,Ol g , 5 g of cali-
internal diameter 3,2 mm approximately, packed
bration fat (5.5) into each of seven vials (6.1). Close
with an acid-washed and silanized diatomaceous
each vial with a septum and a cap (6.2).
earth support of particle size 150 pm to 180 pm
(Chromosorb P NAW 60-80 mesh’) is suitable),
To six of the seven vials (6.1) add, using a syringe (6.4
and coated with 10 % squalane or any other phase
or 6.5), the quantity of solvent (5.1) specified in
permitting the chromatographic separation re-
table 1 to obtain the concentrations indicated. Do not
quired, or
add solvent to the seventh vial.
b) a glass capillary column, approximately 30 m long
Shake vigorously, in the shaking machine (6.9) for
and of 0,3 mm internal diameter, coated with
1 h at room temperature, the six vials to which sol-
methylpolysiloxane of film thickness 0,2 pm.
vent was added.
The injector and detector temperature shall be set at
9.1.2 At the end of this time add, by means of a
100 “C and the oven temperature at 50 “C.
syringe (6.4), 5 ~1 + 0,l ~1 of internal standard (5.2) to
If a capillary column [see b)] is used, the apparatus
each of the seven-vials through the septum.
shall have a l/l 00 split injection system.
NOTE 5 For hexane contents between IO mg/kg and
NOTE 3 For analyses in series, a headspace gas 20 mg/kg, it is preferable to add 2 ~1 of internal standard
chromatograph with automatic sample injection and tem- (5.2).
I) Chromosorb P NAW 60-80 is an example of a suitable product available commercially. This information is given for the
convenience of users of this International Standard and does not constitute an endorsement by IS0 of this product.
2) IS0 5555:1991, Animal and vegetable fats and oils - Sampling.
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IS0 9832: 1992(E)
Table 1 - Hexane content in the calibration samples
Volume of solvent (5.1) added Hexane content (mg/kg) when using
technical hexane n-hexane
PI
67 66
Of5
134 132
1
268 264
2
536 5
...