Pulps — Determination of carbohydrate composition

This method describes the determination of the carbohydrate composition in wood pulp samples. This method makes it possible to determine concentrations of individual anhydrous monosaccharides down to 1 mg/g oven-dry pulp.

Pâtes — Détermination de la composition des hydrates de carbone

General Information

Status
Published
Publication Date
07-Dec-2020
Current Stage
6060 - International Standard published
Start Date
08-Dec-2020
Completion Date
08-Dec-2020
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INTERNATIONAL ISO
STANDARD 21437
First edition
2020-12
Pulps — Determination of
carbohydrate composition
Pâtes — Détermination de la composition des hydrates de carbone
Reference number
ISO 21437:2020(E)
ISO 2020
---------------------- Page: 1 ----------------------
ISO 21437:2020(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2020

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2020 – All rights reserved
---------------------- Page: 2 ----------------------
ISO 21437:2020(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Apparatus ..................................................................................................................................................................................................................... 1

6 Reagents ........................................................................................................................................................................................................................ 2

7 Sampling ........................................................................................................................................................................................................................ 3

8 Test Specimens ....................................................................................................................................................................................................... 4

9 Procedure..................................................................................................................................................................................................................... 4

9.1 Determination of dry matter content .................................................................................................................................. 4

9.2 Test specimen preparation for acid hydrolysis ........................................................................................................... 4

9.3 Hydrolysis .................................................................................................................................................................................................... 4

9.4 Determination of monosaccharides ..................................................................................................................................... 4

9.4.1 Determination using an IC instrument ......................................................................................................... 5

9.4.2 Determination using a GC instrument........................................................................................................... 5

10 Calculation .................................................................................................................................................................................................................. 7

11 Precision ....................................................................................................................................................................................................................... 8

12 Test Report .................................................................................................................................................................................................................. 8

Annex A (informative) Precision ............................................................................................................................................................................... 9

Bibliography .............................................................................................................................................................................................................................15

© ISO 2020 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO 21437:2020(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 of the voluntary nature of standards, 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

www .iso .org/ iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2020 – All rights reserved
---------------------- Page: 4 ----------------------
ISO 21437:2020(E)
Introduction

The carbohydrate composition - the contents of the five principal, neutral monosaccharides; arabinose,

galactose, glucose, xylose and mannose - provides chemical information about the main polysaccharides

in wood pulps. The most commonly-used methods are based on acid hydrolysis of the polysaccharides

using sulfuric acid, followed by subsequent chromatographic determination of the monosaccharides.

This document describes a method for the determination of the contents of the five principal, neutral

monosaccharides; arabinose, galactose, glucose, xylose and mannose, as they appear in wood pulps. The

procedure is based on the sulfuric acid hydrolysis of the samples. The monosaccharides are determined

either by using high performance anion exchange chromatography with a pulsed amperometric detector

(HPAEC-PAD) – subsequently referred to as ion chromatography (IC), or by using gas chromatography

with a flame ionization detector (GC-FID) – subsequently referred to as gas chromatography (GC).

The determination of carbohydrate composition can also be carried out by HPLC (High Performance

Liquid Chromatography), as described, for example, in Reference [3], provided that the results have

been validated against those obtained with this document.
© ISO 2020 – All rights reserved v
---------------------- Page: 5 ----------------------
INTERNATIONAL STANDARD ISO 21437:2020(E)
Pulps — Determination of carbohydrate composition
1 Scope

This method describes the determination of the carbohydrate composition in wood pulp samples. This

method makes it possible to determine concentrations of individual anhydrous monosaccharides down

to 1 mg/g oven-dry pulp.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 638, Paper, board and pulps — Determination of dry matter content — Oven-drying method

ISO 7213, Pulps — Sampling for testing
ISO 14453, Pulps — Determination of acetone-soluble matter
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
carbohydrate composition

amounts of the five principal, neutral monosaccharides; arabinose, galactose, glucose, mannose and

xylose, in a sample, in milligrams per gram
4 Principle

The pulp samples are hydrolysed with sulfuric acid using a two-step technique. The amounts of the

different monosaccharides are determined using either ion chromatography (IC) or gas chromatography

(GC) in the presence of an internal standard to validate the results. If GC is used, the hydrolysed sample

is reduced and acetylated, and the resulting alditol acetates of the monosaccharides are then separated

and determined by GC.
5 Apparatus
5.1 Grinder with a 40 mesh screen or equivalent equipment.

5.2 Filtration equipment: filtering flask; filtering crucible, fritted glass, medium or fine porosity,

30 ml; adapter for the filtering crucible, siphon tube (optional).
© ISO 2020 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO 21437:2020(E)

NOTE The choice of fritted glass porosity depends on the rate of filtration of the particular type of sample.

For slow filtering samples, the use of medium (M) porosity is preferable. In low-yield sulfite pulps especially,

lignin forms a fine dispersion and clogs the pores of the filter. Filtration can be facilitated by using a medium

porosity crucible with a disc of fine porosity glass-fibre filter paper fitted over the sintered glass in the crucible.

Other types of filtering crucibles, such as alundum or porous porcelain crucibles lined with a mat of

glass fibres can also be used.

5.3 Constant temperature water bath, capable of maintaining a temperature of 30 ± 1 °C.

5.4 Autoclave, capable of maintaining a temperature of 120 ± 3 °C.

5.5 Drying oven, 105 ± 2 °C for determining dry matter content in accordance with ISO 638.

The apparatus in 5.6 is used for IC determination only:

5.6 Ion chromatograph (IC) with an anion-exchange column for monosaccharide determination and

pulsed amperometric detector (PAD).
Apparatuses in 5.7 and 5.8 are used for GC-determinations only:
5.7 Water bath, maintained at a temperature of 40 ± 0,5 °C.

5.8 Gas chromatograph (GC) with a suitable column for monosaccharide determination and flame

ionization detector (FID).
6 Reagents
All chemicals shall be of reagent grade or better, unless otherwise indicated.
6.1 Water of high purity, distilled or deionized
6.2 Monosaccharide standards

Monosaccharide standards, for calibration: arabinose, galactose, glucose, mannose and xylose.

Prepare standard solutions of appropriate concentrations, each standard solution containing all five

monosaccharides.

6.3 Sulfuric acid, 72 % w/w (specific gravity 1,633 8 at 20 °C). 72 % sulfuric acid can be prepared

from concentrated sulfuric acid as follows:

Slowly add 650 ml of concentrated sulfuric acid (H SO sp gr 1,84) to 400 ml of water, while cooling

2 4

under a cold-water tap. When the temperature has reached equilibrium with the ambient temperature,

adjust the specific gravity of the acid solution to 1,633 8 with the use of a hydrometer, by careful

addition of concentrated sulfuric acid or water.
NOTE 72 % H SO is also available commercially.
2 4
6.4 Eluent solution (for IC determination)

The composition of this solution depends on the type of IC column to be used. Therefore, follow the

recommendations given by the IC column supplier.
2 © ISO 2020 – All rights reserved
---------------------- Page: 7 ----------------------
ISO 21437:2020(E)
Reagents 6.5 to 6.12 are required only for GC determinations.

NOTE Alternative reagents (to those in 6.5 to 6.12) and procedures (to those in 9.4.2.1, 9.4.2.2, and 9.4.2.3)

[2]

for the neutralization, reduction and derivatization steps, such as those described in TAPPI T249 , can also be

used provided this is indicated in the report.
6.5 Ammonia, NH conc. 25 %
6.5.1 Ammonia 13 M
Mix 9 parts ammonia (25 %) with 1 part of water.
6.6 Potassium hydroxide, KOH
6.6.1 Potassium hydroxide 7,5 M

Weigh 105 g KOH pellets into a 250 ml beaker. Add approx. 150 ml water while stirring. Transfer the

solution into a 250 ml volumetric flask, using an additional 20-30 ml of water to rinse the beaker in

order to complete the transfer.

The reaction is exothermic; heat is evolved. Allow the solution to cool to ambient temperature and

dilute to the mark with water.
6.7 Potassium borohydride, KBH
6.7.1 Potassium borohydride solution

Dissolve 150 mg KBH in 250 µl 13 M NH and 750 µl distilled water in a septum vial (4 ml).

4 3
This solution shall be freshly prepared every day before use.
6.8 Acetic acid, CH COOH, conc.
6.9 Acetic acid anhydride, conc.
6.10 1-methylimidazole
6.11 Ethanol, 95 - 99 %
6.12 Sodium sulfate, Na SO , water-free
2 4
6.13 2-Deoxy-galactose
6.13.1 Internal standard solution, 2-deoxy-galactose 20 mg/ml

Weigh 1,00 g 2-deoxy-galactose to the nearest 0,1 mg, transfer it quantitatively to a 50 ml volumetric

flask, and dilute to the mark with distilled water.

Other internal standards than 2-deoxy-galactose, such as fucose or myo-inositol, can also be used.

However, this shall be specified in the report.
7 Sampling

If the analysis is being made to evaluate a lot of a consignment of pulp, the sample shall be taken in

accordance with ISO 7213. If the analysis is made on another type of sample, report the origin of the

sample, and if possible, the sampling procedure. Pulp samples shall be ground before analysis using an

© ISO 2020 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO 21437:2020(E)

appropriate grinder (5.1). Groundwood and high yield pulps containing a significant amount of resins

shall be extracted with acetone according to ISO 14453 before testing.

NOTE Resins, if not extracted from the pulp prior to analysis, would remain insoluble in acid and can

interfere with the determination of carbohydrate composition.

NOTE Acetone is considered an effective solvent for extracting resin from pulp. Dichloromethane and

ethanol/benzene (1:2), as specified in other methods, are not recommended due to health hazards. In particular,

benzene is a confirmed carcinogen.
8 Test Specimens

Make sure that the test portions taken are representative of the sample received.

9 Procedure
Carry out the preparation and testing in duplicate.
9.1 Determination of dry matter content

Determine the dry matter content of the pulp according to ISO 638 by drying a 2-3 g specimen in an

oven (5.5) at 105 °C ± 2 °C to constant weight. If the pulp needs to be pre-extracted, the dry matter

content shall be determined on the extracted pulp.
9.2 Test specimen preparation for acid hydrolysis

Weigh a portion, of the sample from Clause 7, of 300 ± 10 mg to the nearest 0,1 mg into a glass beaker

with a volume of at least 150 ml.
Calculate and record the oven-dry mass M of the test specimen, in grams.
9.3 Hydrolysis

To the test specimen in the beaker, add exactly 3 ml of 72 % sulfuric acid (6.3) with a pipette. Stir the

contents of the beaker with a glass rod until the test material begins to dissolve. Leave the glass rod in

the beaker.

NOTE Some pulps do not absorb the acid and therefore do not disperse readily. In such cases, after addition

of acid, place the beaker under vacuum in a vacuum desiccator for at least 15 min to facilitate wetting and

absorption.

Place the beaker in a 30 ± 1 °C water bath (5.3) for 1 h. Stir occasionally with the glass rod. Add 84 ml of

water (6.1), using some of this water to rinse the glass rod, making sure all the washing is captured in

the beaker.

Cover the beaker with aluminium foil and place it in autoclave (5.4) at 120 ± 3 °C for 1 h. Allow the

beaker and its contents to cool to approximately 80 °C.
9.4 Determination of monosaccharides
Carry out the determination according to either 9.4.1 or 9.4.2.

NOTE The determination of carbohydrate composition can also be carried out by HPLC (High Performance

Liquid Chromatography), as described in Reference [3] for example, provided that the results have been validated

against those obtained with this document.
4 © ISO 2020 – All rights reserved
-------------------
...

DRAFT INTERNATIONAL STANDARD
ISO/DIS 21437
ISO/TC 6 Secretariat: SCC
Voting begins on: Voting terminates on:
2019-12-20 2020-03-13
Pulps — Determination of carbohydrate composition
Pâtes — Détermination de la composition en carbohydrate
ICS: 85.040
THIS DOCUMENT IS A DRAFT CIRCULATED
FOR COMMENT AND APPROVAL. IT IS
THEREFORE SUBJECT TO CHANGE AND MAY
NOT BE REFERRED TO AS AN INTERNATIONAL
STANDARD UNTIL PUBLISHED AS SUCH.
IN ADDITION TO THEIR EVALUATION AS
BEING ACCEPTABLE FOR INDUSTRIAL,
This document is circulated as received from the committee secretariat.
TECHNOLOGICAL, COMMERCIAL AND
USER PURPOSES, DRAFT INTERNATIONAL
STANDARDS MAY ON OCCASION HAVE TO
BE CONSIDERED IN THE LIGHT OF THEIR
POTENTIAL TO BECOME STANDARDS TO
WHICH REFERENCE MAY BE MADE IN
Reference number
NATIONAL REGULATIONS.
ISO/DIS 21437:2019(E)
RECIPIENTS OF THIS DRAFT ARE INVITED
TO SUBMIT, WITH THEIR COMMENTS,
NOTIFICATION OF ANY RELEVANT PATENT
RIGHTS OF WHICH THEY ARE AWARE AND TO
PROVIDE SUPPORTING DOCUMENTATION. ISO 2019
---------------------- Page: 1 ----------------------
ISO/DIS 21437:2019(E)
COPYRIGHT PROTECTED DOCUMENT
© ISO 2019

All rights reserved. Unless otherwise specified, or required in the context of its implementation, 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
CP 401 • Ch. de Blandonnet 8
CH-1214 Vernier, Geneva
Phone: +41 22 749 01 11
Fax: +41 22 749 09 47
Email: copyright@iso.org
Website: www.iso.org
Published in Switzerland
ii © ISO 2019 – All rights reserved
---------------------- Page: 2 ----------------------
ISO/DIS 21437:2019(E)
Contents Page

Foreword ........................................................................................................................................................................................................................................iv

Introduction ..................................................................................................................................................................................................................................v

1 Scope ................................................................................................................................................................................................................................. 1

2 Normative references ...................................................................................................................................................................................... 1

3 Terms and definitions ..................................................................................................................................................................................... 1

4 Principle ........................................................................................................................................................................................................................ 1

5 Apparatus ..................................................................................................................................................................................................................... 1

6 Reagents ........................................................................................................................................................................................................................ 2

7 Sampling ........................................................................................................................................................................................................................ 3

8 Test Specimens ....................................................................................................................................................................................................... 3

9 Procedure..................................................................................................................................................................................................................... 3

9.1 Determination of dry matter content .................................................................................................................................. 4

9.2 Test specimen preparation for acid hydrolysis ........................................................................................................... 4

9.3 Hydrolysis .................................................................................................................................................................................................... 4

9.4 Determination of monosaccharides ..................................................................................................................................... 4

9.4.1 Determination using an IC instrument ......................................................................................................... 4

9.4.2 Determination using a GC instrument........................................................................................................... 5

10 Calculation .................................................................................................................................................................................................................. 6

11 Precision ....................................................................................................................................................................................................................... 7

12 Test Report .................................................................................................................................................................................................................. 7

Annex A (informative) Precision ............................................................................................................................................................................... 8

Bibliography .............................................................................................................................................................................................................................13

© ISO 2019 – All rights reserved iii
---------------------- Page: 3 ----------------------
ISO/DIS 21437:2019(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 of the voluntary nature of standards, 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 www .iso .org/

iso/ foreword .html.

This document was prepared by Technical Committee ISO/TC 6, Paper, board and pulps.

Any feedback or questions on this document should be directed to the user’s national standards body. A

complete listing of these bodies can be found at www .iso .org/ members .html.
iv © ISO 2019 – All rights reserved
---------------------- Page: 4 ----------------------
ISO/DIS 21437:2019(E)
Introduction

The carbohydrate composition - the contents of the five principal, neutral monosaccharides; arabinose,

galactose, glucose, xylose and mannose - provides chemical information about the main polysaccharides

in wood pulps. The most commonly used methods are based on acid hydrolysis of the polysaccharides

using sulphuric acid, followed by subsequent chromatographic determination of the monosaccharides.

This document describes a method for the determination of the contents of the five principal,

neutral monosaccharides; arabinose, galactose, glucose, xylose and mannose, as they appear in wood

pulps. The procedure is based on the sulphuric acid hydrolysis of the samples. The monosaccharides

are determined either by using high performance anion exchange chromatography with a pulsed

amperometric detector (HPAEC-PAD) – subsequently referred to as ion chromatography (IC), or by

using gas chromatography with a flame ionization detector (GC-FID) – subsequently referred to as gas

chromatography (GC).
© ISO 2019 – All rights reserved v
---------------------- Page: 5 ----------------------
DRAFT INTERNATIONAL STANDARD ISO/DIS 21437:2019(E)
Pulps — Determination of carbohydrate composition
1 Scope

This method describes the determination of the carbohydrate composition in wood pulp samples. This

method makes it possible to determine concentrations of individual anhydrous monosaccharides down

to 1 mg/g oven-dry pulp.
2 Normative references

The following referenced documents are indispensable for the application of this document. For dated

references, only the edition cited applies. For undated references, the latest edition of the referenced

document (including any amendments) applies.

ISO 638, Paper, board and pulps — Determination of dry matter content — Oven-drying method

ISO 7213, Pulps — Sampling for testing
ISO 14453, Pulps — Determination of acetone-soluble matter
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at http:// www .electropedia .org/
3.1
Carbohydrate composition

Amounts of the five principal, neutral monosaccharides; arabinose, galactose, glucose, mannose and

xylose, in a sample, in milligrams per gram.
4 Principle

The pulp samples are hydrolysed with sulphuric acid using a two-step technique. The amounts of the

different monosaccharides are determined using either ion chromatography (IC) or gas chromatography

(GC) in the presence of an internal standard to validate the results If GC is used, the hydrolysed sample

is reduced and acetylated, and the resulting alditol acetates of the monosaccharides are then separated

and determined by GC.
5 Apparatus
5.1 Grinder with a 40 mesh screen or equivalent equipment.
5.2 Water bath at a temperature of (30 ± 1) °C.
5.3 Autoclave at a temperature of (120 ± 3) °C
© ISO 2019 – All rights reserved 1
---------------------- Page: 6 ----------------------
ISO/DIS 21437:2019(E)

5.4 Drying oven, (105 ± 2) °C for determining dry matter content in accordance with ISO 638

The apparatus in 5.5 is used for IC determination only:

5.5 Ion-chromatograph (IC) with an anion-exchange column for monosaccharide determination and

pulsed amperometric detector (PAD).
Apparatuses in 5.6-5.7 are used for GC-determinations only:
5.6 Water bath at a temperature of (40 ± 0,5) °C

5.7 Gas chromatograph (GC) with a suitable column for monosaccharide determination and flame

ionization detector (FID).
6 Reagents
All chemicals shall be of reagent grade or better, unless otherwise indicated
6.1 Water of high purity, distilled or deionized
6.2 Monosaccharide standards

Monosaccharide standards, for calibration: arabinose, galactose, glucose, mannose and xylose.

Prepare standard solutions of appropriate concentrations, each standard solution containing all five

monosaccharides.

6.3 Sulphuric acid, 72% Prepare as follows: Add 300 ml of water to 1000 ml volumetric flask. Add

slowly 670 ml of concentrated sulphuric acid (H SO sp gr 1,84) while cooling under a cold water tap.

2 4

When the temperature has reached equilibrium with the ambient temperature, dilute to the mark and mix.

72% H SO is also available commercially.
2 4
6.4 Eluent solution (for IC determination)

The composition of this solution depends on the type of IC column to be used. Therefore, follow the

recommendations given by the IC column supplier.
The following reagents are required only for GC determinations:
6.5 Ammonia, NH conc. 25 %
6.5.1 Ammonia 12 M
Mix 9 parts ammonia (25 %) with 1 part of water.
6.6 Potassium hydroxide, KOH,
6.6.1 Potassium hydroxide 7.5 M

Weigh 123 g KOH pellets into a 250 ml beaker. Add approx. 150 ml water while stirring. Transfer the

solution into a 250 ml volumetric flask, using an additional 20-30 ml of water to rinse the beaker in

order to complete the transfer.

The reaction is exothermic, heat is evolved. Allow the solution to cool to ambient temperature and

dilute to the mark with water.
2 © ISO 2019 – All rights reserved
---------------------- Page: 7 ----------------------
ISO/DIS 21437:2019(E)
6.7 Potassium borohydride, KBH
6.7.1 Potassium borohydride solution

Dissolve 150 mg KBH in 250 µl 12 M NH and 750 µl distilled water in a septum vial (4 ml).

4 3
This solution shall be freshly prepared every day before use.
6.8 Acetic acid, CH COOH, conc.
6.9 Acetic acid anhydride, conc.
6.10 1-methylimidazole
6.11 Ethanol, 95-99 %
6.12 Sodium sulphate, Na SO , water-free
2 4
6.13 2-Deoxy-galactose
6.13.1 Internal standard solution, 2-deoxy-galactose 20 mg/ml

Weigh 1,00 g 2-deoxy-galactose to the nearest 0.1 mg, transfer it quantitatively to a 50 ml volumetric

flask, and dilute to the mark with distilled water.

Note to entry: Other internal standards than 2-deoxy-galactose, such as fucose or myo-inositol, can also

be used. However, this must be specified in the report.
7 Sampling

If the analysis is being made to evaluate a lot of a consignment of pulp, the sample shall be taken in

accordance with ISO 7213. If the analysis is made on another type of sample, report the origin of the

sample, and if possible the sampling procedure. Pulp samples shall be ground before analysis using an

appropriate grinder (5.1). Groundwood and high yield pulps containing a significant amount of resins

shall be extracted with acetone according to ISO 14453 before testing.

Note 1 to entry Resins, if not extracted from the pulp prior to analysis, would remain insoluble in acid

and may interfere with the determination of carbohydrate composition.

Note 2 to entry: Acetone is considered an effective solvent for extracting resin from pulp.

Dichloromethane and ethanol/benzene (1:2), as specified in other methods, are not recommended due

to health hazards. In particular, benzene is a confirmed carcinogen.
8 Test Specimens

Make sure that the test portions taken are representative of the sample received.

9 Procedure
Carry out the preparation and testing in duplicate.
© ISO 2019 – All rights reserved 3
---------------------- Page: 8 ----------------------
ISO/DIS 21437:2019(E)
9.1 Determination of dry matter content

Determine the dry matter content of the pulp according to ISO 638 by drying a 2-3 g specimen in an

oven at 105°C +/- 2°C to constant weight. If the pulp has to be pre-extracted, the dry matter content

content shall be determined on the extracted pulp.
9.2 Test specimen preparation for acid hydrolysis

Weigh a portion, of the sample from clause 7, of (300 ± 10) mg to the nearest 0,1 mg into a glass beaker

with a volume of at least 150 ml.
Calculate and record the oven-dry weight W of the test specimen , in grams.
9.3 Hydrolysis
To the test specimen in the beaker, add exactly 3 ml of 72 % sulphuric acid (6.3
...

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