1、Designation: E1721 01 (Reapproved 2015)Standard Test Method forDetermination of Acid-Insoluble Residue in Biomass1This standard is issued under the fixed designation E1721; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year o
2、f last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () 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
3、main chain of which 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 fr
4、actions with sulfuric 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, a
5、nd newsprint), 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. Anindepen
6、dent nitrogen analysis 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 s
7、ample includes both acid-soluble lignin and lignin inthe acid insoluble residue.1.4 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.5 This standard does not purport to address all of thesafety concerns, if any, associated with
8、 its use. It is theresponsibility of the user of this standard to establish 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 Standa
9、rds:2E1690 Test Method for Determination of Ethanol Extrac-tives in BiomassE1756 Test Method for Determination of Total Solids inBiomassE1757 Practice for Preparation of Biomass for Composi-tional Analysis3. Terminology3.1 Definitions:3.1.1 acid-insoluble residuethe solid residue, correctedfor acid-
10、insoluble ash, retained on a medium-porosity filtercrucible after the 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 Practi
11、ce E1757 in order to raise the total solidscontent above 85 %, based on an oven-dried solids weight.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-ins
12、oluble residue analysis are af-fected by the incomplete hydrolysis of biomass. The resultswill be biased high unless the sample is hydrolyzed completely.1This test method is under the jurisdiction of ASTM Committee E48 onBioenergy and Industrial Chemicals from Biomass and is the direct responsibilit
13、y ofSubcommittee E48.05 on Biomass Conversion.Current edition approved June 1, 2015. Published July 2015. Originally approvedin 1995. Last previous edition approved in 2009 as E1721-01(2009). DOI:10.1520/E1721-01R15.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM
14、 Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1Take care to mix the acid/bioma
15、ss slurry thoroughly during theconcentrated acid hydrolysis.5.2 The results of acid-insoluble residue analysis are af-fected by the timing of the acid digestion steps. The insolubleresidue will dissolve slowly into solution in an irreproduciblefashion. The timing within this test method must be foll
16、owedclosely.6. Apparatus6.1 Analytical Balance, readable to 0.1 mg.6.2 Convection Oven, with a temperature control of 105 63C.6.3 Muffle FurnaceAn electric furnace is recommendedfor igniting the sample. The furnace should be fitted with anindicating pyrometer or thermocouple so that the requiredtemp
17、erature 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 anhydrous 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,
18、18 M 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 Filtering 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 car
19、efully.8.2 Use caution when handling glass bottles after theautoclave step since they may become pressurized.9. Sampling, Test Specimens, and 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 P
20、ractice E1757.9.1.2 Extractives-free material prepared in accordance withTest Method E1690.9.2 The test specimen shall consist of approximately 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
21、, but the weight of thematerial must be corrected to 105C dry weight by using thepercent total solids value determined in accordance with TestMethod E1756, prior to calculating the acid-insoluble residue.9.3 The samples for total solids determination should beweighed out at the same time as those fo
22、r acid-insolubleresidue determination. If this is performed later, it can intro-duce an error in the calculation because ground biomass cangain 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
23、to achieve a constant weight of60.3 mg. Store the ignited crucibles in a desiccator untilneeded.NOTE 1In order to determine the absolute amounts 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.1
24、0.2 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 % sulfuric 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 mixe
25、d 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 reduced 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 c
26、ompletemixing 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 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 hydrolysi
27、s 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 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
28、 with caution after theautoclave step since they may become pressurized.10.9 After completion of the autoclave cycle, allow thesamples to 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
29、filtering crucible.10.11 If a carbohydrate analysis or acid-soluble ligninanalysis, or both, is desired, decant 15 to 25 mL of filtrate intoa resealable container. If the aliquot is not used immediately forfurther analysis, store it in a refrigerator at 4C.NOTE 5Acid-soluble lignin should be analyze
30、d within 24 h andpreferably within6hofhydrolysis.10.12 Use hot water to wash any particles clinging to theglass bottle into the crucible 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 achie
31、ved of 60.3 mg uponreheating.E1721 01 (2015)210.14 Cool in the desiccator and record the weight, W2,ofthe crucible, acid insoluble residue, and acid-insoluble 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, orunti
32、l all the carbon is eliminated. Heat at a rate of 10C/min toprevent flaming. The container should be partially coveredduring this step if the sample tends to flame. Avoid heatingabove the maximum stated temperature. Protect the test con-tainer from strong drafts at all times to prevent mechanical lo
33、ssof 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. Calculation11.1 If the biomass was prepared in accordance with Part Bor C of Practice E1757, calculate the percent acid-insolubleresidue on a 105C dry-weight
34、 basis as follows:% acid insoluble residueW22 W3W13T105Tprep3100 (1)where:W1= initial sample weight,W2= weight of the crucible, acid-insoluble residue, andacid-insoluble ash,W3= weight of the crucible and acid-insoluble ash,T105= % total solids determined at 105C as determined inaccordance with Test
35、 Method E1756, andTprep=%Tfdor % T45as determined by Practice E1757.11.2 If the biomass was prepared in accordance with Part Aof Practice E1757 or in accordance with Test Method E1756,calculate the percent acid-insoluble residue on a 105C dry-weight basis as follows:% acid insoluble residueW22 W3W13
36、T1051003100 (2)where:W1= initial sample weight,W2= weight of the crucible, acid-insoluble residue, andacid-insoluble ash,W3= weight of the crucible and acid-insoluble ash, andT105= %total solids determined at 105C as determined inaccordance with Test Method E1756.12. Report12.1 Report the percent ac
37、id-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 replicate 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
38、 poplarsample in six different laboratories yielded a standard deviationof 2.37 % and a CV % of 9.92 %.14. Keywords14.1 acid-insoluble lignin; agricultural residue; biomass;fermentation residue; herbaceous; lignin; wastepaper; woodASTM International takes no position respecting the validity of any p
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41、mments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your 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 copyrigh
42、ted 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). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 01 (2015)3
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