ISO 24215:2022

INTERNATIONAL ISO
STANDARD 24215
First edition
2022-06
Lignins — Determination of
carbohydrate composition in kraft
lignin, soda lignin and hydrolysis
lignin
Reference number
© ISO 2022
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
Contents Page
Foreword .iv
Introduction .v
1 Scope . 1
2 Normative references . 1
3 Terms and definitions . 1
4 Principle . 2
5 Apparatus . 2
6 Reagents . 3
7 Sampling . 4
8 Drying . 4
9 Test Specimens . 5
10 Procedure .5
10.1 General . 5
10.2 Hydrolysis . 5
10.3 Determination of monosaccharides . 5
10.3.1 General . 5
10.3.2 Determination using an IC instrument . 5
10.3.3 Determination using a GC instrument . 6
11 Calculation . 7
12 Precision . 8
13 Test Report . 8
Annex A (informative) Precision .10
Annex B (informative) Comparison of GC/FID and IC/PAD analyses of carbohydrates .14
Bibliography .15
iii
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
Introduction
There is a rapidly-growing worldwide interest in developing novel applications for lignin as a
replacement for fossil-based raw materials in products including carbon fibre, adhesives, thermoplastics,
resins, composites, and various chemicals. In addition, the use of lignin in these and other applications
will offload recovery boilers in pulp mills, allowing more efficient recovery of pulping chemicals and
increased pulp production. These benefits translate into reduced environmental impact and improved
sustainability owing to the use of renewable materials.
In order to ensure harmonization of testing practices among lignin producers and to facilitate trade,
the use of international standard methods is needed to characterize the lignin raw material for a wide
range of properties such as general composition, functional groups, molecular weight distribution,
particle size, structural features, and thermal behaviour and stability.
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 lignin. The total content and composition of carbohydrates also provide an indication of the purity
of the lignin isolated from the kraft pulping process (kraft lignin) or the soda pulping process (soda
lignin), or that obtained by hydrolysis of biomass (hydrolysis lignin).
[1][2]
The methods described in this document are based on those described in other publications .
[3] [4][5][6]
Although the principle is similar to that described in ISO 21437 and other related methods
for the determination of carbohydrates in pulp, the properties and end-use applications of lignin, as
well as several steps in the testing procedure, including sampling, sample preparation, and others, are
different from those of pulp.
v
INTERNATIONAL STANDARD ISO 24215:2022(E)
Lignins — Determination of carbohydrate composition in
kraft lignin, soda lignin and hydrolysis lignin
1 Scope
This document describes a method for the determination of carbohydrate composition in kraft lignin,
soda lignin and biorefinery lignin.
The method is applicable to lignin isolated from a kraft pulping process, a soda pulping process, or
lignin obtained by hydrolysis of biomass.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https:// www .iso .org/ obp
— IEC Electropedia: available at https:// www .electropedia .org/
3.1
lignins
class of complex organic macromolecules, containing aromatic sub-units, that play a key role in the
formation of cell walls in wood and bark, conferring mechanical strength and rigidity to the cell walls
and to plants as a whole
Note 1 to entry: Lignin is the main non-carbohydrate constituent of wood.
3.2
kraft lignin
depolymerized and chemically modified lignin isolated from a kraft pulping process, such as that
originating from kraft black liquor
3.3
soda lignin
depolymerized and chemically modified lignin isolated from a soda pulping process, such as that
originating from soda liquor
3.4
hydrolysis lignin
lignin produced for commercial applications by conversion of biomass, through enzymatic or acid
hydrolysis, into sugars and lignin streams, followed by separation of the lignin fraction
3.5
biomass
biological material derived from living, or previously living organisms, such as wood, agricultural
crops, and other plant-based biodegradable material
3.6
acid-insoluble lignin
Klason lignin
residue after treating wood or pulp with sulfuric acid in a two-step hydrolysis procedure to solubilize
the carbohydrates into monosaccharides
3.7
acid-soluble lignin
portion of lignin that is soluble during the acid-insoluble lignin determination
3.8
carbohydrate composition
amounts of the five principal, neutral monosaccharides; arabinose, galactose, glucose, mannose and
xylose, in a sample
4 Principle
A lignin sample is treated with sulfuric acid in a two-step (primary and secondary) hydrolysis process
to dissolve the carbohydrates. The acid-insoluble lignin is filtered off. The filtrate consists of hydrolysed
carbohydrates and a small amount of acid-soluble lignin. The amounts of the different monosaccharides
in the filtrate 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 Filtration equipment
5.1.1 Filtering flask, 250 ml.
5.1.2 Gooch filtering crucible, fritted glass, medium or fine porosity, 30 ml; adapter for the filtering
crucible, siphon tube (optional).
NOTE 1 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. 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.
NOTE 2 Other types of filtering crucibles, such as alundum or porous porcelain crucibles lined with a mat of
fine fibres can also be used.
5.2 Constant temperature water bath, capable of maintaining a temperature of (30 ± 1) °C.
5.3 Autoclave, capable of maintaining a temperature of (120 ± 3) °C.
5.4 Drying oven, conduction type, maintained at (105 ± 2) °C.
A convection oven shall not be used, as this could lead to increased flare-ups and fire hazard, as well as
loss of sample due to material being ejected from the crucible.
5.5 Analytical balance, accurate to 0,1 mg.
5.6 Equipment specific to the determination method
5.6.1 IC determination
Ion chromatograph (IC) with an anion-exchange column for monosaccharide determination and
pulsed amperometric detector (PAD)
5.6
...