EN ISO 15512:2016

SLOVENSKI STANDARD
01-januar-2017
1DGRPHãþD
SIST EN ISO 15512:2014
3ROLPHUQLPDWHULDOL'RORþHYDQMHYRGH,62
Plastics - Determination of water content (ISO 15512:2016)
Kunststoffe - Bestimmung des Wassergehaltes (ISO 15512:2016)
Plastiques - Dosage de l'eau (ISO 15512:2016)
Ta slovenski standard je istoveten z: EN ISO 15512:2016
ICS:
83.080.01 Polimerni materiali na Plastics in general
splošno
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN ISO 15512
EUROPEAN STANDARD
NORME EUROPÉENNE
November 2016
EUROPÄISCHE NORM
ICS 83.080.01 Supersedes EN ISO 15512:2014
English Version
Plastics - Determination of water content (ISO
15512:2016)
Plastiques - Dosage de l'eau (ISO 15512:2016) Kunststoffe - Bestimmung des Wassergehaltes (ISO
15512:2016)
This European Standard was approved by CEN on 29 September 2016.

CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this
European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references
concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN
member.
This European Standard exists in three official versions (English, French, German). A version in any other language made by
translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management
Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,
Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and
United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN ISO 15512:2016 E
worldwide for CEN national Members.

Contents Page
European foreword . 3

European foreword
This document (EN ISO 15512:2016) has been prepared by Technical Committee ISO/TC 61 “Plastics”
in collaboration with Technical Committee CEN/TC 249 “Plastics” the secretariat of which is held by
NBN.
This European Standard shall be given the status of a national standard, either by publication of an
identical text or by endorsement, at the latest by May 2017, and conflicting national standards shall be
withdrawn at the latest by May 2017.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
This document supersedes EN ISO 15512:2014.
According to the CEN-CENELEC Internal Regulations, the national standards organizations of the
following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria,
Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia,
France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey and the United Kingdom.
Endorsement notice
The text of ISO 15512:2016 has been approved by CEN as EN ISO 15512:2016 without any modification.
INTERNATIONAL ISO
STANDARD 15512
Fourth edition
2016-10-15
Plastics — Determination of water
content
Plastiques — Dosage de l’eau
Reference number
ISO 15512:2016(E)
©
ISO 2016
ISO 15512:2016(E)
© ISO 2016, Published in Switzerland
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form
or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior
written permission. Permission can be requested from either ISO at the address below or ISO’s member body in the country of
the requester.
ISO copyright office
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CH-1214 Vernier, Geneva, Switzerland
Tel. +41 22 749 01 11
Fax +41 22 749 09 47
copyright@iso.org
www.iso.org
ii © ISO 2016 – All rights reserved

ISO 15512:2016(E)
Contents Page
Foreword .v
Introduction .vi
1 Scope . 1
2 Normative references . 1
3 Method A — Extraction with anhydrous methanol . 1
3.1 Principle . 1
3.2 Reagents. 2
3.3 Apparatus . 2
3.4 Preparation of test sample . 2
3.4.1 Granules or powder . 2
3.4.2 Finished articles . 2
3.5 Procedure . 3
3.5.1 Precautions . 3
3.5.2 Preparation of test portions . 3
3.5.3 Determination . 3
3.6 Expression of results . 3
3.7 Precision . 4
4 Method B1 — Water vaporization using a heating tube oven . 4
4.1 Principle . 4
4.2 Reagents. 4
4.3 Apparatus . 5
4.4 Preparation of test sample . 7
4.5 Procedure . 7
4.5.1 Precautions . 7
4.5.2 Preparation of apparatus . 7
4.5.3 Equipment check . 7
4.5.4 Determination . 8
4.6 Expression of results . 8
4.7 Precision . 9
5 Method B2 — Water vaporization using a heated sample vial . 9
5.1 Principle . 9
5.2 Reagents. 9
5.3 Apparatus .10
5.4 Preparation of test sample .11
5.5 Procedure .12
5.5.1 Preparation of apparatus .12
5.5.2 Equipment check .12
5.5.3 Determination .12
5.6 Expression of results .14
5.7 Precision .14
6 Method C — Manometric method .15
6.1 Principle .15
6.2 Reagents.15
6.3 Apparatus .15
6.4 Preparation of test sample .16
6.5 Procedure .16
6.5.1 Equipment .16
6.5.2 Outgassing .17
6.5.3 Calibration .17
6.5.4 Determination .19
6.6 Expression of results .20
6.7 Precision .20
ISO 15512:2016(E)
7 Test report .20
Annex A (informative) Alternative sample preparation methods and titration methods .21
Annex B (informative) Selection of the optimum heating temperature for the water
content determination .22
Annex C (normative) Determination of the water content of a water standard .24
Bibliography .25
iv © ISO 2016 – All rights reserved

ISO 15512:2016(E)
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.
The procedures used to develop this document and those intended for its further maintenance are
described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the
different types of ISO documents should be noted. This document was drafted in accordance with the
editorial rules of the ISO/IEC Directives, Part 2 (see www.iso.org/directives).
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. Details of
any patent rights identified during the development of the document will be in the Introduction and/or
on the ISO list of patent declarations received (see www.iso.org/patents).
Any trade name used in this document is information given for the convenience of users and does not
constitute an endorsement.
For an explanation on the meaning of ISO specific terms and expressions related to conformity
assessment, as well as information about ISO’s adherence to the World Trade Organization (WTO)
principles in the Technical Barriers to Trade (TBT) see the following URL: Foreword – Supplementary
information
The committee responsible for this document is ISO/TC 61, Plastics, Subcommittee SC 5, Physical-
chemical properties.
This fourth edition cancels and replaces the third edition (ISO 15512:2014), of which it constitutes a
minor revision to update information in 6.2.1.
ISO 15512:2016(E)
Introduction
The interlaboratory comparability of the water content determination of plastics is often low. Major
causes for this are the sample packaging, sample handling, and differences between equipment and
settings. Samples have to, e.g. be packed in special glass containers or water barrier sealed bags.
Sample handling is preferably to be carried out in a dry nitrogen or air environment. For improving the
repeatability and reproducibility, the procedure prescribed in this International Standard is intended
to be followed strictly.
The temperature settings for the vaporization method are not specified in this International Standard.
For the manometric method, a temperature of 200 °C is often used. However, for some condensation
materials, this might be too high and could, e.g. cause generation of water due to a condensation
reaction.
The heating temperature has to be optimized concerning the material to be tested, the equipment in
use, and the practical circumstances. If the temperature is too low, the total amount of water in the
material to be tested will not be evaporated completely, whereas too high temperatures cause water
generation due to effects like degradation and condensation reactions.
In this International Standard, a procedure is included for optimization of the heating temperature
in order to choose the correct temperature for the water content determination and to improve the
interlaboratory comparability.
vi © ISO 2016 – All rights reserved

INTERNATIONAL STANDARD ISO 15512:2016(E)
Plastics — Determination of water content
1 Scope
1.1 This International Standard specifies methods for the determination of the water content of plastics
in the form of powder, granules, and finished articles. These methods do not test for water absorption
(kinetics and equilibrium) of plastics as measured by ISO 62.
Method A is suitable for the determination of water content as low as 0,1 % with an accuracy of 0,1 %.
Method B and Method C are suitable for the determination of water content as low as 0,01 % with an
accuracy of 0,01 %.
Water content is an important parameter for processing materials and has to remain below the level
specified in the appropriate material standard.
1.2 Four alternative methods are specified in this International Standard.
— Method A is an extraction method using anhydrous methanol followed by a Karl Fischer titration
of the extracted water. It can be used for all plastics and is applicable to granules smaller than
4 mm × 4 mm × 3 mm. The method can also be used for, e.g. prepolymer materials in the form of a
powder that are insoluble in methanol.
— Method B1 is a vaporization method using a tube oven. The water contained in the test portion is
vaporized and carried to the titration cell by a dry air or nitrogen carrier gas, followed by a Karl
Fischer titration of the collected water. It can be used for all plastics and is applicable to granules
smaller than 4 mm × 4 mm × 3 mm.
— Method B2 is a vaporization method using a heated sample vial. The water contained in the test
portion is vaporized and carried to the titration cell by a dry air or nitrogen carrier gas, followed
by a Karl Fischer titration of the collected water. It can be used for all plastics and is applicable to
granules smaller than 4 mm × 4 mm × 3 mm.
— Method C is a manometric method. The water content is determined from the increase in pressure,
which results when the water is evaporated under a vacuum. This method is not applicable to plastic
samples containing volatile compounds, other than water, in amounts contributing significantly
to the vapour pressure at room temperature. Checks for the presence of large amounts of volatile
compounds are to be carried out periodically, for example by gas chromatography. Such checks are
particularly required for new types or grades of material.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. For dated references, only the edition cited applies. For undated
references, the latest edition of the referenced document (including any amendments) applies.
ISO 760, Determination of water — Karl Fischer method (General method)
3 Method A — Extraction with anhydrous methanol
3.1 Principle
A test portion is extracted with anhydrous methanol and the extracted water determined by titration
using the Karl Fischer method.
ISO 15512:2016(E)
3.2 Reagents
During the analysis, use only reagents of recognized analytical grade.
3.2.1 Titration medium, methanol anhydrous, having a water content less than 0,1 % by mass. Other
solvents can be used if shown to be comparable.
3.2.2 Karl Fischer reagent, with an equivalence factor of approximately 3 mg/ml to 5 mg/ml of water.
When the reagent is prepared, check its equivalence factor as specified in ISO 760.
3.3 Apparatus
Ordinary laboratory apparatus and the following.
3.3.1 Glass flasks, approximately 250 ml capacity, provided with a suitable cap preventing moisture
uptake or release.
3.3.2 Conical titration flasks, approximately 150 ml capacity, with standard ground necks and
provided with ground-glass stoppers.
3.3.3 Reflux condensers, with ground neck capable of being fitted on to the flasks (3.3.2) and on to
the tubes (3.3.4).
3.3.4 Water-absorption tubes with ground joints, containing calcium chloride or other suitable
drying agent.
3.3.5 Heaters, suitable for the conical titration flasks (3.3.2).
3.3.6 Desiccator, containing a suitable desiccant.
3.3.7 Analytical balance, accurate to 0,2 mg.
3.3.8 Karl Fischer apparatus, for determining water content in accordance with ISO 760.
3.4 Preparation of test sample
3.4.1 Granules or powder
Take a representative sample of approximately 100 g. Put the sample into a pre-dried glass flask (3.3.1)
and immediately close it with a stopper.
NOTE It is desirable to pre-dry the container in an oven and then cool it over a suitable desiccant.
3.4.2 Finished articles
Cut or saw the sample into pieces of appropriate size, i.e. having a maximum size of 4 mm × 4 mm × 3 mm.
Proceed quickly to minimize moisture absorption.
2 © ISO 2016 – All rights reserved

ISO 15512:2016(E)
3.5 Procedure
3.5.1 Precautions
Due to the low quantities of water measured, maximum care shall be exercised at all times to avoid
contaminating the sample with water from the sample container, the atmosphere, or transfer
equipment. Hygroscopic resin samples shall be protected from the atmosphere.
3.5.2 Preparation of test portions
Conduct the test on two test portions from the same sample. Use test portions containing 10 mg to
20 mg of water based on the estimated water content of the sample.
Using modern coulometric Karl Fischer titration instruments test portions containing less than 10 mg
can be applied if the same level of accuracy of results can be achieved.
3.5.3 Determination
Carefully dry the apparatus.
Weigh each test portion to the nearest 1 mg into a conical titration flask (3.3.2) fitted with a ground-
glass stopper. Pipette 50 ml of anhydrous methanol (3.2.1) into the conical flask containing the test
portion. At the same time, pipette 50 ml of anhydrous methanol to another conical flask for a blank test.
Stopper the flasks. Keep the stoppered flasks in the desiccator (3.3.6) pending continuation of the test.
Unstopper the flasks and quickly attach them to reflux condensers (3.3.3) fitted with calcium chloride
tubes (3.3.4). Reflux the contents of the conical flasks for 3 h, then leave them for 45 min to cool to
room temperature. Separate the flasks from the condensers, quickly stopper them, and place them in
the desiccator.
Use the Karl Fischer apparatus (3.3.8) to titrate the contents of each flask with Karl Fischer reagent
(3.2.2).
NOTE Alternative sample preparation methods and titration methods are given in Annex A.
3.6 Expression of results
The water content, w, expressed as a percentage by mass, for each of the two determinations is given by
Formula (1):
VV− ×T
()
(1)
w= ×100
m
where
V is the volume, expressed in millilitres, of Karl Fischer reagent used for the determination;
V is the volume, expressed in millilitres, of Karl Fischer reagent used for the blank test;
T is the water equivalent, expressed in grams of water per millilitre of reagent, of Karl Fischer
reagent;
m is the mass, in grams, of the test portion.
NOTE For some equipment, V might not be available separately but only used for internal calculation of
V - V . In this case, the numerator in the formula simplifies to V × T.
1 2
ISO 15512:2016(E)
The two values for the water content shall not differ by more than 10 % relative or 0,02 % absolute,
whichever is the greater. If the difference is greater, repeat the measurements until acceptable
consecutive values are obtained and discard all unacceptable results.
The result is expressed as the average of these two determinations, rounded to the nearest 0,01 %
by mass.
3.7 Precision
The precision of this test method is not known because interlaboratory data are not available. If and
when interlaboratory data are obtained, a precision statement will be added to a subsequent revision.
For comparison of data between two laboratories, special care needs to be taken on sample packing
and sample handling.
4 Method B1 — Water vaporization using a heating tube oven
4.1 Principle
The sample is weighed then placed in an oven. The water contained in the test portion is vaporized
and carried to the titration cell by a dry nitrogen carrier gas. The water is then titrated using the
coulometric Karl Fischer method. This method is based on the reduction of iodine by sulfur dioxide in
the presence of water to form sulfur trioxide and hydroiodic acid as follows:
I + SO + H O → 2HI + SO
2 2 2 3
Unlike the conventional Karl Fischer reagents that include iodine, the coulometric technique generates
the iodine electrolytically from iodide:
− −
2I → I + 2e
with 10,71 C of generating current corresponding to 1 mg of water in accordance with Faraday’s Law.
4.2 Reagents
During the analysis, use only reagents of recognized analytical grade.
4.2.1 Anode solution, containing iodide ions to generate iodine in the reaction mixture, in accordance
with the equipment manufacturer’s instructions.
4.2.2 Cathode solution, containing a suitable salt in methanol (or another suitable organic solvent),
prepared in accordance with the equipment manufacturer’s instructions.
4.2.3 Universal single anode reagent, containing iodide ions to generate iodine in the reaction
mixture, in accordance with the equipment manufacturer’s instructions, for use in a diaphragm-free cell.
NOTE A universal single anode coulometric reagent is applied in diaphragm-free titration cells. Titration
cells with diaphragm require the use of a separate anode and cathode solution.
4.2.4 Neutralization solution, consisting of approximately 4 mg/ml of water in propylene carbonate,
ethylene glycol monomethyl ether (2-methoxyethanol), or methyl cellosolve.
4.2.5 Nitrogen gas (N ), containing less than 5 μg/g of water.
4 © ISO 2016 – All rights reserved

ISO 15512:2016(E)
4.3 Apparatus
Ordinary laboratory apparatus and the following.
4.3.1 Coulometric Karl Fischer titrator, consisting of a control unit and a titration-cell assembly
equipped with a generator cell, with or without diaphragm, dual platinum sensing electrodes, and a
magnetic stirrer (see Figure 1).
The instrument is designed to coulometrically generate iodine that reacts stoichiometrically with the
water present in the cell. The coulombs of electricity required to generate the reagent are converted to
micrograms of water and is given as a direct digital readout.
NOTE A diaphragm-free cell is accurate enough for many applications. However, some applications may
require a diaphragm for the best possible accuracy. This can be checked with the equipment supplier.
4.3.2 Water vaporizer, consisting of an oven capable of heating the sample to at least 300 °C, a heating
tube (see Figure 2), a temperature control unit, a carrier-gas flow meter, and carrier-gas drying tubes
containing desiccant.
4.3.3 Microsyringe, with capacity of 10 μl, calibrated.
4.3.4 Sample boat.
Aluminium foil can be used to hand-fashion a disposable boat large enough to contain the sample and
small enough to fit into the heating tube.
4.3.5 Suitable desiccant, for the carrier-gas drying tubes (4.3.2).
4.3.6 Molecular sieve, pore size 0,3 nm, desiccant for carrier gas.
4.3.7 PTFE sleeves, to be used to maintain the air-tightness of the ground glass joints of the system.
Alternatively, grease, containing little or no water and having low water absorptivity, can be used.
ISO 15512:2016(E)
Key
1 coulometric Karl Fischer meter 7 oven
2 exhaust gas 8 heating tube
3 titration cell 9 water-absorption tubes (filled with desiccant, for example P O )
2 5
4 titration controller 10 flow meter
5 power supply 11 temperature controller
6 water vaporizer 12 N gas
Figure 1 — Flowchart of a system used for the determination of water content using method B1
a) Push-bar type
b) Magnet type
Key
1 sample boat 3 sample-boat inlet
2 sample inlet 4 magnet
Figure 2 — Heating tubes
6 © ISO 2016 – All rights reserved

ISO 15512:2016(E)
4.4 Preparation of test sample
The test material can be in any form, such as granules, moulding powder, fabricated shapes, or
moulded items.
Cut fabricated shapes and moulded items to a suitable size. Granules shall be smaller than
4 mm × 4 mm × 3 mm.
Take a representative sample of ≤ 10 g. Due to the small size of the sample, care shall be taken to ensure
that it is in fact representative.
4.5 Procedure
4.5.1 Precautions
Due to the low quantities of water measured, maximum care shall be exercised at all times to avoid
contaminating the sample with water from the sample container, the atmosphere, or transfer
equipment. Hygroscopic resin samples shall be protected from the atmosphere.
4.5.2 Preparation of apparatus
Refer to Figure 1 for the following procedure.
Assemble the water vaporizer (4.3.2) and coulometric Karl Fischer titrator (4.3.1) as directed in the
manufacturer’s instructions. Fill the absorption tubes with desiccating agent (4.3.2) as directed in the
manufacturer’s instructions.
Pour approximately 200 ml (adjust for the container size) of the anode solution (4.2.1) into the generator
cell and 10 ml of the cathode solution (4.2.2) into the cathode solution cell (4.3.1). The surface of the
cathode solution shall be below the level of the anode solution to prevent backflow contamination of the
cathode solution.
NOTE A universal single anode coulometric reagent is applied in diaphragm-free titration cells. Titration
cells with diaphragm require the use of a separate anode and cathode solution.
Turn the cell power switch on. If the cell potential shows a negative value, indicating that the anode
solution contains an excess of iodine, add 50 μl to 200 μl of the neutralization solution (4.2.4).
Disconnect the tube connecting the vaporizer unit to the titration cell. Set the carrier gas flow to
200 ml/min to 300 ml/min and heat the oven to the desired temperature to remove any residual water
from the vaporizer (4.3.2).
Lift the titration cell and agitate the solution by gently swirling the cell to remove any residual water
from the walls. Stir the solution for a minute in the “TITRATION” mode to dry and stabilize the inner
atmosphere.
Reconnect the tube from the vaporizer unit to the titration cell. Keep the carrier-gas flow on during the
whole titration. The instrument is then ready for sample analysis.
4.5.3 Equipment check
To check if the coulometric Karl Fischer titrator is functioning properly, carry out a determination with
a known amount of water as follows. With the analyser stabilized and in the “READY” position, press
the start switch and carefully inject 5 µl of distilled water into the cell using a 10 µl syringe (4.3.3).
When the “END” light comes on, record the reading. This reading should be (5 000 ± 250) µg.
To check if the whole system is functioning properly, carry out a determination with 50 mg of sodium
tartrate dihydrate (Na C H O ·2H O) at 150 °C. Follow 4.5.4 to measure the quantity of water contained
2 4 4 6 2
in the sodium tartrate dihydrate. The result should be (15,6 ± 0,5) %.
ISO 15512:2016(E)
4.5.4 Determination
Heat the oven to the desired temperature and place the sample boat (4.3.4) in the heating tube and push
it into the oven to dry and also to back purge any residual water contained in the sample-boat inlet.
For the heating temperature, refer to the material standard. As the heating temperature is also
dependent on equipment used and the practical circumstances, the heating temperature has to be
optimized using the method described in Annex B. If the heating temperature is not mentioned in the
material standard or if there is no material standard, then use the method mentioned in Annex B to
determine the optimum heating temperature.
After a few minutes, move the sample boat to the sample inlet port and allow it to cool.
Weigh a test portion of the sample (4.4) directly into the sample boat (which will have to be removed
from the heating tube for this purpose) or on to a piece of aluminium foil (see next paragraph).
Appropriate sizes of test portion are given in Table 1.
If the sample boat is made of glass or another material which is not designed to be discarded after use, a
piece of aluminium foil can be wrapped around the test portion to prevent the test portion from sticking
to the boat when it melts. Wrapping the test portion in this way will also prevent it from scattering
during introduction into the sample boat.
If the test portion was weighed directly into the sample boat, place the sample boat back into the
heating tube as quickly as possible. If the test portion was weighed on to a piece of aluminium foil, wrap
it, and introduce it, again as quickly as possible, into the sample boat either through the sample inlet or
the sample-boat inlet.
Table 1 — Recommended mass of test portion
Expected water content Mass of test portion
w m
% by mass g
w > 1 0,2 > m ≥ 0,1
1 ≥ w > 0,5 0,4 > m ≥ 0,2
0,5 ≥ w > 0,1 1 > m ≥ 0,4
0,1 ≥ w m ≥ 1
Verify that the instrument is in the “READY” status. Press the “START” key. Move the sample boat into
the oven (see Figure 2). Allow the titration to proceed until the “END” light comes on and then record
the instrument reading in micrograms.
4.6 Expression of results
Calculate the water content, w, in the test portion, expressed as a percentage by mass by using
Formula (2):
m
− 4
water
w = ×10
(2)
m
test portion
where
m is the mass of water found in the test portion, in micrograms;
water
m is the mass of the test portion, in grams.
test portion
8 © ISO 2016 – All rights reserved

ISO 15512:2016(E)
4.7 Precision
The precision of this test method is not known because interlaboratory data are not available. If and
when interlaboratory data are obtained, a precision statement will be added to a subsequent revision.
For comparison of data between two laboratories, special care needs to be taken on sample packing
and sample handling.
5 Method B2 — Water vaporization using a heated sample vial
5.1 Principle
The sample is weighed into a sample vial and placed in an oven. The water contained in the test portion
is vaporized and carried to the titration cell by a dry nitrogen carrier gas. The water is then titrated
using the coulometric Karl Fischer method. This method is based on the reduction of iodine by sulfur
dioxide in the presence of water to form sulfur trioxide and hydroiodic acid as follows:
I + SO + H O → 2HI + SO
2 2 2 3
Unlike the conventional Karl Fischer reagents that include iodine, the coulometric technique generates
the iodine electrolytically from iodide:
− −
2I → I + 2e
with 10,71 C of generating current corresponding to 1 mg of water in accordance with Faraday’s Law.
5.2 Reagents
Only reagents of recognized analytical grade shall be used.
5.2.1 Anode solution, containing iodide ions to generate iodine in the reaction mixture, in accordance
with the equipment manufacturer’s instructions.
5.2.2 Cathode solution, containing a suitable salt in methanol (or another suitable organic solvent),
prepared in accordance with the equipment manufacturer’s instructions.
5.2.3 Universal single anode reagent, containing iodide ions to generate iodine in the reaction
mixture, in accordance with the equipment manufacturer’s instructions, for use in a diaphragm-free cell.
NOTE A universal single anode coulometric reagent is applied in diaphragm-free titration cells. Titration
cells with diaphragm require the use of a separate anode and cathode solution.
5.2.4 Titration medium, methanol, anhydrous, having a water content < 0,1 % by mass. Other solvents
can be used if shown to be comparable.
5.2.5 Water standard 1 %, inorganic substance, water content 1 % (m/m), every lot individually
certified.
NOTE The water content can be verified with the method given in Annex C.
3 3
5.2.6 Nitrogen gas (N ), flow of ≥ 60 cm /min and preferably containing less than 1 mg/m of water
(dew point −80 °C).
3 3
NOTE 1 A nitrogen flow of 60 cm /min with a water concentration of 1 mg/m corresponds with a water
contribution to the titration cell of 0,06 μg H O/min.
ISO 15512:2016(E)
NOTE 2 For some equipment, a nitrogen flow of ≤ 60 cm /min can cause a failure.
5.3 Apparatus
Ordinary laboratory apparatus and the following.
5.3.1 Coulometric Karl Fischer titrator, consisting of a control unit and a titration-cell assembly
equipped with a diaphragm-free generator electrode, dual platinum sensing electrodes, and a magnetic
stirrer.
The instrument is designed to coulometrically generate iodine, which reacts stoichiometrically with
the water present in the cell. The number of coulombs of electricity required to generate the reagent
are converted to micrograms of water, presented as a direct digital readout. Adjust the instrument to
a start criterion of < 20 μg H O/min and a stop criterion of < 5 μg H O/min. Adjust the integration time
2 2
for both criteria to 60 s.
The coulometric Karl Fischer titrator is schematically shown in Figure 3.
NOTE 1 A diaphragm-free cell is accurate enough for many applications. A cell with a diaphragm may be
required for the best possible accuracy.
NOTE 2 The start criterion of < 20 μg H O/min and the stop criterion of < 5 μg H O/min are default values
2 2
and applicable for most plastics. In case of analysing low concentrations of water, these values might need to be
reduced.
NOTE 3 An integration time of 60 s showed to be a suitable starting point for both start and stop criterion.
5.3.2 PTFE sleeves, to be used to maintain the air-tightness of the ground glass joints of the system.
Alternatively, grease, containing little or no water and having low water absorptivity, can be used.
5.3.3 Molecular sieve, pore size 0,3 nm, desiccant for carrier gas.
5.3.4 Water vaporizer, consisting of an oven or a heating device capable of heating a test portion in
a sample vial (5.3.5) to at least 300 °C, a temperature control unit, carrier gas, drying tubes containing a
molecular sieve, and a carrier gas flow meter.
5.3.5 Sample vials, glass, to be used in the water vaporizer.
The sample vials are dried in a drying oven and kept dry in a desiccator. Sample vials with a capacity of
6 ml are recommended.
5.3.6 Aluminium crimp caps, equipped with a silicone septum, to be used with sample vials.
The crimp caps are dried in a drying oven and kept in a desiccator. Other suitable caps can also be used.
5.3.7 Analytical balance, accurate to 0,1 mg.
5.3.8 Drying oven, temperature 105 °C.
5.3.9 Desiccator, containing an efficient desiccant.
5.3.10 Glass flasks, approximately 250 ml capacity, provided with a suitable cap preventing moisture
uptake and release.
10 © ISO 2016 – All rights reserved

ISO 15512:2016(E)
5.3.11 Aluminium foil seal bags, approximately 250 g capacity, or other suitable storage container
preventing moisture uptake and release.
Key
1 nitrogen supply 7 titration vessel
2 molecular sieve 8 dual platinum electrode
3 oven sample processor 9 generator electrode
4 water vaporizer oven 10 piston burette
5 sample vial 11 universal reagent
6 absorber tube 12 coulometric Karl Fischer titrator
Figure 3 — System setup for the determination o
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