ASTM E1721-01(2020)
(Test Method)Standard Test Method for Determination of Acid-Insoluble Residue in Biomass
Standard Test Method for Determination of Acid-Insoluble Residue in Biomass
SIGNIFICANCE AND USE
4.1 The acid-insoluble residue content is used in conjunction with other assays to determine the total composition of biomass samples.
SCOPE
1.1 This test method covers determination of the acid-insoluble residue of hard and soft woods, herbaceous materials (such as switchgrass and sericea), agricultural residues (such as corn stover, wheat straw, and bagasse), wastepaper (such as office waste, boxboard, and newsprint), acid and alkaline pretreated biomass, and the solid fraction of fermentation residues. All results are reported relative to the 105 °C oven-dried weight of the sample.
1.2 The residue collected contains the acid-insoluble lignin and any condensed proteins from the original sample. An independent nitrogen analysis would be required to determine the acid-insoluble lignin content separate from the condensed protein fraction and is outside the scope of this test method.
1.3 A portion of the lignin in some biomass samples will remain soluble during this procedure. The total lignin in a biomass sample includes both acid-soluble lignin and lignin in the acid insoluble residue.
1.4 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific hazards statements are given in Section 8 and Note 2 and Note 4.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
General Information
Relations
Standards Content (Sample)
This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
Designation: E1721 − 01 (Reapproved 2020)
Standard Test Method for
Determination of Acid-Insoluble Residue in Biomass
This standard is issued under the fixed designation E1721; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
INTRODUCTION
Biomass is composed largely of the following: cellulose, a polymer of glucose; hemicellulose, a
complex polymer, the main chain of which consists of xylans or glucomannans; and lignin, a complex
phenolic polymer. The lignin is mostly insoluble in mineral acids, unlike the other cell wall
components of biomass. For this reason, lignin can be analyzed gravimetrically after hydrolyzing the
cellulose and hemicellulose fractions with sulfuric acid.
1. Scope 1.6 This international standard was developed in accor-
dance with internationally recognized principles on standard-
1.1 This test method covers determination of the acid-
ization established in the Decision on Principles for the
insoluble residue of hard and soft woods, herbaceous materials
Development of International Standards, Guides and Recom-
(suchasswitchgrassandsericea),agriculturalresidues(suchas
mendations issued by the World Trade Organization Technical
corn stover, wheat straw, and bagasse), wastepaper (such as
Barriers to Trade (TBT) Committee.
office waste, boxboard, and newsprint), acid and alkaline
pretreated biomass, and the solid fraction of fermentation
2. Referenced Documents
residues. All results are reported relative to the 105 °C oven-
2.1 ASTM Standards:
dried weight of the sample.
E1690 Test Method for Determination of Ethanol Extrac-
1.2 The residue collected contains the acid-insoluble lignin
tives in Biomass
and any condensed proteins from the original sample. An
E1756 Test Method for Determination of Total Solids in
independent nitrogen analysis would be required to determine
Biomass
the acid-insoluble lignin content separate from the condensed
E1757 Practice for Preparation of Biomass for Composi-
protein fraction and is outside the scope of this test method.
tional Analysis
1.3 A portion of the lignin in some biomass samples will
3. Terminology
remain soluble during this procedure. The total lignin in a
biomass sample includes both acid-soluble lignin and lignin in
3.1 Definitions:
the acid insoluble residue.
3.1.1 acid-insoluble residue—the solid residue, corrected
for acid-insoluble ash, retained on a medium-porosity filter
1.4 The values stated in SI units are to be regarded as
crucible after the primary 72 % and secondary 4 % H SO
standard. No other units of measurement are included in this 2 4
hydrolysis described in this test method. This material is
standard.
primarily acid-insoluble lignin and any condensed proteins.
1.5 This standard does not purport to address all of the
3.1.2 prepared biomass—material that has been treated in
safety concerns, if any, associated with its use. It is the
accordancewithPracticeE1757inordertoraisethetotalsolids
responsibility of the user of this standard to establish appro-
content above 85 %, based on an oven-dried solids weight.
priate safety, health, and environmental practices and deter-
mine the applicability of regulatory limitations prior to use.
4. Significance and Use
Specific hazards statements are given in Section 8 and Note 2
4.1 The acid-insoluble residue content is used in conjunc-
and Note 4.
tion with other assays to determine the total composition of
biomass samples.
This test method is under the jurisdiction of ASTM Committee E48 on
Bioenergy and Industrial Chemicals from Biomass and is the direct responsibility of
Subcommittee E48.05 on Biomass Conversion. For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Current edition approved July 1, 2020. Published August 2020. Originally contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
approved in 1995. Last previous edition approved in 2015 as E1721 – 01(2015). Standards volume information, refer to the standard’s Document Summary page on
DOI: 10.1520/E1721-01R20. the ASTM website.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1721 − 01 (2020)
5. Interferences 9.3 The samples for total solids determination should be
weighed out at the same time as those for acid-insoluble
5.1 The results of acid-insoluble residue analysis are af-
residue determination. If this is performed later, it can intro-
fected by the incomplete hydrolysis of biomass. The results
duce an error in the calculation because ground biomass can
willbebiasedhighunlessthesampleishydrolyzedcompletely.
gain or lose moisture rapidly when exposed to the atmosphere.
Take care to mix the acid/biomass slurry thoroughly during the
concentrated acid hydrolysis.
10. Procedure
5.2 The results of acid-insoluble residue analysis are af-
10.1 Label the crucibles needed for analysis individually,
fected by the timing of the acid digestion steps. The insoluble
and ignite them at 575 6 25 °C to achieve a constant weight of
residue will dissolve slowly into solution in an irreproducible
60.3 mg. Store the ignited crucibles in a desiccator until
fashion. The timing within this test method must be followed
needed.
closely.
NOTE 1—In order to determine the absolute amounts of acid-insoluble
6. Apparatus
residue and acid-insoluble ash, for quality control purposes, it is useful to
weigh and record the ignited crucible to the nearest 0.1 mg.
6.1 Analytical Balance, readable to 0.1 mg.
10.2 Weigha0.3 60.01-gsampletothenearest0.1mg,and
6.2 Convection Oven, with a temperature control of 105 6
place it in a test tube. Record the initial weight as W .
3 °C.
NOTE 2—Warning: 72 % sulfuric acid is very corrosive and should be
6.3 Muffle Furnace—An electric furnace is recommended
handled only by trained personnel.
for igniting the sample. The furnace should be fitted with an
10.3 Add 3.00 6 0.01 mL (4.92 6 0.01 g) of 72 % H SO ,
indicating pyrometer or thermocouple so that the required 2 4
and stir for 1 min or until mixed thoroughly.
temperature of 575 6 25 °C can be maintained.
10.4 Place the test tube in the water bath controlled to 30 6
6.4 Autoclave, capable of maintaining 121 6 3 °C.
1 °C, and hydrolyze for 2 h.
6.5 Water Bath, set at 30 6 1 °C.
NOTE 3—The hydrolysis time may be reduced to1hifthe dried sample
6.6 Desiccator, using anhydrous calcium sulfate.
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