SIST EN ISO 5381:1998

SLOVENSKI STANDARD
SIST EN ISO 5381:1998
01-november-1998
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Starch hydrolysis products - Determination of water content - Modified Karl Fischer
method (ISO 5381:1983)
Stärkehydrolysenprodukte - Bestimmung des Wassergehalts - Modifiziertes Karl-Fischer-
Verfahren (ISO 5381:1983)
Produits d'hydrolyse de l'amidon ou de la fécule - Dosage de l'eau - Méthode Karl
Fischer modifiée (ISO 5381:1983)
Ta slovenski standard je istoveten z: EN ISO 5381:1994
ICS:
67.180.20 Škrob in izdelki iz njega Starch and derived products
SIST EN ISO 5381:1998 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN ISO 5381:1998

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SIST EN ISO 5381:1998

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SIST EN ISO 5381:1998

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SIST EN ISO 5381:1998
International Standard
INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONWE)YHAPO~HAR OP~AHH3ALWlR fl0 CTAHIIlA~l+l3ALWWORGANISATION INTERNATIONALE DE NORMALISATION
Starch hydrolysis products - Determination of water
Modified Karl Fischer method
content -
Produits d’hydrolyse de l’amidon ou de Ia fkule - Dosage de l’eau - AMhode Karl Fisher modifiee
First edition - 1983-08-01
UDC 664.2 : 543.812
w Ref. No. ISO 53814983 (EI
-
sp
Descriptors : carbo-hydrates, starches, food starch, tests, determination of content, water, Karl Fischer reagent, test equipment.
Price based on 6 pages

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SIST EN ISO 5381:1998
Foreword
ISQ (the international Organization for Standardization) is a woridwide federation of
national Standards bodies WO member bedies). The work of developing International
Standards is carried out through ISO technical committees. Every member body
interested in a subject for which a technical committee has been authorized 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.
Draft International Standards adopted by the technical committees are circulated to
the member bodies for approval before their acceptance as International Standards by
the ISO Council.
international Standard ISO 5381 was developed by Technical Committee ISCVTC 93,
Sta& (including derivatives and by-products), and was circulated to the member
bodies in April 1982.
lt has been approved by the member bodies of the following countries :
Canada
Germany, F. R. South Africa, Rep. of
Egypt, Arab Rep. of Netherlands
USA
France
Roland USSR
No member body expressed disapproval of the document.
International Organkation for Standardkation, 1983
Printed in Switzerland

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SIST EN ISO 5381:1998
ISO 5381-1983 (E)
INTERNATIONAL STANDARD
Starch hydrolysis products - Determination of water
Modified Karl Fischer method
content -
5.1 “Stabilized” Karl Fischer reagent.
0 lntroduction
The stabilized reagent is commercially available in the form of a
This International Standard is based on the method described
prepared Solution. It is also possible to prepare the reagent in
in ISO 760. However, it has been improved by determining the
the laboratory (sec ISO 760).
content directly using the methanoi/formamide solvent.
5.2 MethanoVformamide solvent.
1 Scope and field of application
Mix 700 mi of anhydrous methanol with 300 ml of anhydrous
formamide.
This International Standard specifies a method for the deter-
mination of the water content of starch hydrolysis products.
This reagent shail be handied with care.
5.3 Sodium tartrate, crystalline (Na2C4H406 . 2H,O).
2 Reference
This product is commercially available in the form “speciai
ISO 760, Determination of water - Karl Fischer method
quaiity for Karl Fischer”. If this quality cannot be obtained,
(General methodl.
wash the tartrate with 10 ml of the methanol/formamide sol-
vent (5.2), and carry out an appropriate blank test.
3 Principle
Crush the product so that it Passes completely through a sieve
of nominal aperture size 250 Pm, complying with the re-
Reaction of a Solution of iodine, sulphur dioxide, pyridine and
quirements of ISO 565. The water content of this hydrate is ap-
2methoxyethanol (stabilized Karl Fischer reagent) with the
proximately 1566 % (mlm) and shall be checked by vacuum
water contained in the product dispersed previously in a mix-
drying at 150 OC untii constant mass is obtained.
ture of methanol and formamide.
6 Apparatus
4 Reactions
Ordinary laboratory apparatus, in particuiar
HZ0 + l2 + SO2 + 3C,H,N -+ 2C,H,N.HI + C,H,N.S03
6.1 One-mark pipette, of capacity 20 mI.
C5H,N.S03 + ROH + C5H,NH.0S020R
6.2 Devices, into which the Sample to be anaiysed tan be in-
where R is the 2-methoxyethyl radicai.
troduced.
6.2.1 Weighing tube (for solid products), consisting of a test
5 Reagents tube of suitabie diameter so as to ailow the introduction of
sampies, and fitted with a stopper.
During the analysis, use only reagents of recognized analytical
6.2.2 Syringe (for viscous liquid& of capacity 10 ml, for ex-
grade and only distilled water or water of equivaient purity; all
ampie in accordance with annex A.
solvents shall have a water content of less than 0,l % (mhd.

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SIST EN ISO 5381:1998
ISO 5381-1983 (El
a correction taking into account this Change by taking the
6.2.3 One-mark pipettes (for liquid products), of appro- make
same time for standardizing the reagent.
priate capacities.
7.4 Determination
6.3 Karl Fischer titrating eq uipment or similar
illustrations in annex BI.
apparatus tsee the
Preparation of the test Sample
7.4.1
6.4 Analytical balance.
7.4.1 .l Liquid or viscous products
warm slightly to obtain
7 Procedure Mix the laboratory Sample. If necessary,
a homogeneous mixture.
7.1 Preparation of the apparatus
7.4.1.2 Solid products
The reagents shall be standardized for each daily series of tests
Crush the laboratory Sample so that it Passes easily through a
and the apparatus set up in conformity with the manufacturer’s
instructions. sieve of nominal aperture size 500 Fm, complying with the re-
quirements of ISO 565.
If the apparatus has remained assembled for more than 24 h, it
is recommended that the reagent be poured back into the tank
7.4.2 Test Portion
and that the burette be filled several times before commencing
a series of titrations.
7.4.2.1 Liquid or viscous products
If the titration vessel of the apparatus has not been used before,
Using a pipette (6.2.3) or a special syringue (6.2.2), take a
or after emptying, pour in 20 ml of the methanol/formamide
quantity of the test Sample (7.4.1 .l) so that a volume of ap-
solvent (5.2) either by means of a pipette fitted with a bulb
proximately 20 ml of the Karl Fischer reagent is necessary when
(6.1), or by means of the device fitted in the apparatus used.
using a 25 ml burette, corresponding to approximately 120 mg
of water.
This quantity should be adequate for immersing the ends of the
platinum electrodes having adjusted the Position of these elec-
7.4.2.2 Solid products
trodes in such a way as not to obstruct the stirrer during its
rotation.
In the weighing tube (6.2.1), weigh, to the nearest 0,l mg, a
Adjust the rate of stirring and add the Karl Fischer reagent (5.1) quantity of the test Sample (7.4.1.2) so that a volume of
approximately 20 ml of the Karl Fischer reagent is necessary
until the equivalence Point is re
...