1、Designation: E 1721 01Standard Test Method forDetermination of Acid-Insoluble Residue in Biomass1This standard is issued under the fixed designation E 1721; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision.
2、 A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.INTRODUCTIONBiomass is composed largely of the following: cellulose, a polymer of glucose; hemicellulose, acomplex polymer, the main chain of w
3、hich consists of xylans or glucomannans; and lignin, a complexphenolic polymer. The lignin is mostly insoluble in mineral acids, unlike the other cell wallcomponents of biomass. For this reason, lignin can be analyzed gravimetrically after hydrolyzing thecellulose and hemicellulose fractions with su
4、lfuric acid.1. Scope1.1 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 ascorn stover, wheat straw, and bagasse), wastepaper (such asoffice waste, boxboard, and newsprint),
5、acid and alkalinepretreated biomass, and the solid fraction of fermentationresidues. All results are reported relative to the 105C oven-dried weight of the sample.1.2 The residue collected contains the acid-insoluble ligninand any condensed proteins from the original sample. Anindependent nitrogen a
6、nalysis would be required to determinethe acid-insoluble lignin content separate from the condensedprotein fraction and is outside the scope of this test method.1.3 A portion of the lignin in some biomass samples willremain soluble during this procedure. The total lignin in abiomass sample includes
7、both acid-soluble lignin and lignin inthe acid insoluble residue.1.4 The values stated in SI units are to be regarded as thestandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to estab
8、lish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use. Specific hazardsstatements are given in Section 8 and Note 2 and Note 4.2. Referenced Documents2.1 ASTM Standards:2E 1690 Test Method for Determination of Ethanol Extrac-tives in Bi
9、omassE 1756 Test Method for Determination of Total Solids inBiomassE 1757 Practice for Preparation of Biomass for Composi-tional Analysis3. Terminology3.1 Definitions:3.1.1 acid-insoluble residuethe solid residue, correctedfor acid-insoluble ash, retained on a medium-porosity filtercrucible after th
10、e primary 72 % and secondary 4 % H2SO4hydrolysis described in this test method. This material isprimarily acid-insoluble lignin and any condensed proteins.3.1.2 prepared biomassmaterial that has been treated inaccordance with Practice E 1757 in order to raise the totalsolids content above 85 %, base
11、d on an oven-dried solidsweight.4. Significance and Use4.1 The acid-insoluble residue content is used in conjunc-tion with other assays to determine the total composition ofbiomass samples.5. Interferences5.1 The results of acid-insoluble residue analysis are af-fected by the incomplete hydrolysis o
12、f biomass. The resultswill be biased high unless the sample is hydrolyzed completely.1This test method is under the jurisdiction of ASTM Committee E48 onBiotechnology and is the direct responsibility of Subcommittee E48.05 on BiomassConversion.Current edition approved Nov. 10, 2001. Published Februa
13、ry 2002. Orginallypublished as E 1721-95. Last previous edition E 1721-95.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe
14、ASTM website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.Take care to mix the acid/biomass slurry thoroughly during theconcentrated acid hydrolysis.5.2 The results of acid-insoluble residue analysis are af-fected by the timing of
15、 the acid digestion steps. The insolubleresidue will dissolve slowly into solution in an irreproduciblefashion. The timing within this test method must be followedclosely.6. Apparatus6.1 Analytical Balance, readable to 0.1 mg.6.2 Convection Oven, with a temperature control of 105 63C.6.3 Muffle Furn
16、aceAn electric furnace is recommendedfor igniting the sample. The furnace should be fitted with anindicating pyrometer or thermocouple so that the requiredtemperature of 575 6 25C can be maintained.6.4 Autoclave, capable of maintaining 121 6 3C.6.5 Water Bath, set at 30 6 1C.6.6 Desiccator, using an
17、hydrous calcium sulfate.7. Reagents and Materials7.1 Chemicals:7.1.1 72 % H2SO4, specific gravity 1.6389 6 0.0012 at15.6C/15.6C or 12.00 6 0.02 M.7.1.2 Water,18MV deionized.7.2 Materials:7.2.1 Glass Serum Bottles, 125 mL, crimp top style, withrubber stoppers and aluminum seals to fit.7.2.2 Glass Fil
18、tering Crucible, 50 mL, medium porosity,with a nominal maximum pore size of 10 m.7.2.3 Vacuum Adapter for Crucibles.8. Hazards8.1 Handle the sulfuric acid carefully.8.2 Use caution when handling glass bottles after theautoclave step since they may become pressurized.9. Sampling, Test Specimens, and
19、Test Units9.1 Test specimens suitable for analysis with this procedureare as follows:9.1.1 Prepared biomass samples that have been treated inaccordance with Practice E 1757.9.1.2 Extractives-free material prepared in accordance withTest Method E 1690.9.2 The test specimen shall consist of approximat
20、ely 0.3 gof sample obtained in such a manner to ensure that it isrepresentative of the entire lot of material being tested.Prepared biomass is used in this test, but the weight of thematerial must be corrected to 105C dry weight by using thepercent total solids value determined in accordance with Te
21、stMethod E 1756, prior to calculating the acid-insoluble residue.9.3 The samples for total solids determination should beweighed out at the same time as those for acid-insolubleresidue determination. If this is performed later, it can intro-duce an error in the calculation because ground biomass can
22、gain or lose moisture rapidly when exposed to the atmosphere.10. Procedure10.1 Label the crucibles needed for analysis individually,and ignite them at 575 6 25C to achieve a constant weight of60.3 mg. Store the ignited crucibles in a desiccator untilneeded.NOTE 1In order to determine the absolute am
23、ounts of acid-insolubleresidue and acid-insoluble ash, for quality control purposes, it is useful toweigh and record the ignited crucible to the nearest 0.1 mg.10.2 Weigh a 0.3 6 0.01-g sample to the nearest 0.1 mg, andplace it in a test tube. Record the initial weight as W1.NOTE 2Warning: 72 % sulf
24、uric acid is very corrosive and should behandled only by trained personnel.10.3 Add 3.00 6 0.01 mL (4.92 6 0.01 g) of 72 % H2SO4,and stir for 1 min or until mixed thoroughly.10.4 Place the test tube in the water bath controlled to 30 61C, and hydrolyze for 2 h.NOTE 3The hydrolysis time may be reduce
25、d to1hifthedried samplehas been milled and sieved to pass through a 20-mesh sieve and beretained on a 80-mesh sieve.10.5 Stir the sample every 15 min to ensure completemixing and wetting.10.6 Transfer the hydrolyzate to a glass bottle, and dilute toa 4 % acid concentration by adding 84.00 6 0.04 mL
26、water orby bringing the combined weight of sample, acid, and water upto 89.22 6 0.04 g. Be careful to transfer all of the residualsolids along with the hydrolysis liquor.10.7 Stopper each of the bottles, and crimp the aluminumseals into place.10.8 Set the autoclave to a liquid vent cycle to prevent
27、lossof sample from the bottle in the event of a loose crimp seal.Autoclave the samples in their sealed bottles for1hat12163C.NOTE 4Warning: Handle sealed bottles with caution after the auto-clave step since they may become pressurized.10.9 After completion of the autoclave cycle, allow thesamples to
28、 cool for approximately 20 min at room temperaturebefore removing the seals and stoppers.10.10 Vacuum filter the hydrolysis solution through a pre-viously ignited filtering crucible.10.11 If a carbohydrate analysis or acid-soluble ligninanalysis, or both, is desired, decant 15 to 25 mL of filtrate i
29、ntoa resealable container. If the aliquot is not used immediately forfurther analysis, store it in a refrigerator at 4C.NOTE 5Acid-soluble lignin should be analyzed within 24 h andpreferably within6hofhydrolysis.10.12 Use hot water to wash any particles clinging to theglass bottle into the crucible
30、and to wash the filtered residuefree of acid using vacuum filtration.10.13 Dry the crucible and its contents at 105 6 3C for 2h or until a constant weight is achieved of 60.3 mg uponreheating.10.14 Cool in the desiccator and record the weight, W2,ofthe crucible, acid insoluble residue, and acid-inso
31、luble ash tothe nearest 0.1 mg.10.15 Place the crucible and its contents in the mufflefurnace, and ignite at 575 6 25C for a minimum of 3 h, orE1721012until all the carbon is eliminated. Heat at a rate of 10C/min toprevent flaming. The container should be partially coveredduring this step if the sam
32、ple tends to flame. Avoid heatingabove the maximum stated temperature. Protect the test con-tainer from strong drafts at all times to prevent mechanical lossof the test specimen.10.16 Cool in the desiccator, and record the weight, W3,ofthe crucible and acid-insoluble ash to the nearest 0.1 mg.11. Ca
33、lculation11.1 If the biomass was prepared in accordance with Part Bor C of Practice E 1757, calculate the percent acid-insolubleresidue on a 105C dry-weight basis as follows:% acid insoluble residue W22 W3W13T105Tprep3 100 (1)where:W1= initial sample weight,W2= weight of the crucible, acid-insoluble
34、 residue, andacid-insoluble ash,W3= weight of the crucible and acid-insoluble ash,T105= % total solids determined at 105C as determinedin accordance with Test Method E 1756, andTprep=%Tfdor % T45as determined by Practice E 1757.11.2 If the biomass was prepared in accordance with Part Aof Practice E
35、1757 or in accordance with Test Method E 1756,calculate the percent acid-insoluble residue on a 105C dry-weight basis as follows:% acid insoluble residue W22 W3W13T1051003 100 (2)where:W1= initial sample weight,W2= weight of the crucible, acid-insoluble residue, andacid-insoluble ash,W3= weight of t
36、he crucible and acid-insoluble ash, andT105= %total solids determined at 105C as determined inaccordance with Test Method E 1756.12. Report12.1 Report the percent acid-insoluble residue, to two deci-mal places, on a 105C dry-weight basis.13. Precision and Bias13.1 Precision:13.1.1 Data obtained by r
37、eplicate testing of a hybrid poplarin one laboratory yielded a standard deviation of 0.41 % and aCV % of 1.59 %.13.1.2 Data obtained by replicate testing of a hybrid poplarsample in six different laboratories yielded a standard deviationof 2.37 % and a CV % of 9.92 %.14. Keywords14.1 acid-insoluble
38、lignin; agricultural residue; biomass;fermentation residue; herbaceous; lignin; wastepaper; woodASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determin
39、ation of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be reviewed every five years andif not revised, either reapproved or wit
40、hdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that yo
41、ur comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org).E1721013
