1、Designation: D7026 13Standard Guide forSampling and Reporting of Results for Determination ofPercent Biobased Content of Materials via Carbon IsotopeAnalysis1This standard is issued under the fixed designation D7026; the number immediately following the designation indicates the year oforiginal adop
2、tion or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONThe biobased content of a material and the resources consumed in creatio
3、n of the material, bothenergy and raw materials are defined in Guide D6852. These resources are expressed as carbonequivalent. Percent Biobased Carbon Content represents new or recently fixed carbon, opposed tofossil carbon fixed millions of years ago. Test Methods D6866 presents two methods for exp
4、erimen-tally determining the percentage of recently fixed carbon in a sample by means of its radioisotopecontent, allowing direct determination of its biobased content. The following guide represents acompanion document to Test Methods D6866 and defines the sampling and sample handlingprocedures for
5、 the radioisotope methods for determination of biobased content.There are a great variety of biobased materials that may be tested using one of the radioisotopemethods, with a wide range of physical characteristics and special sampling problems.It is not the intent of this guide to provide specific
6、sample collection and handling instructions fora specific material. Rather, the guide presents general outlines to be followed in sampling proceduresand encourages the use of existing material-specific sampling procedures validated by extensive usein industry. The emphasis in the guide is to provide
7、 thorough and transparent reporting that allowssubsequent evaluation of the validity of the claims regards biobased content.1. Scope1.1 This guide provides a framework for collecting andhandling samples for determination of biobased content ofmaterials by means of the carbon isotope method described
8、 inTest Methods D6866. Tests for sampling adequacy based onthe standard statistical tools are provided. In addition, reportingof the results, including sampling techniques and handlingprocedures and chain-of-custody issues are discussed.1.2 This guide is concerned with collecting representativesampl
9、es within a given material or a lot, not with lot-to-lotvariations such as considered in quality control schemes.1.3 Biobased materials often represent sampling problemsspecific to a given material, such as heterogeneity, and so forth,which require employment of material-specific sampling meth-ods.
10、The use of specialized sampling methods already acceptedand validated by industries that manufacture and/or use thebiomaterial is encouraged. However, all sampling techniques,especially non-standard techniques developed for specific ma-terials must be reported in sufficient detail to allow criticala
11、ssessment of the techniques used.1.4 Carbon isotope analysis involves thermal processing inpresence of oxidants. Compatibility of any given material withTest Methods D6866 must be assessed. Special attention mustbe given to materials with potential for explosion hazards, suchas peroxides, nitrated c
12、ompounds, azides, and so forth. Ex-amples of peroxide-forming compounds are ethers, someketones and a number of other compounds.1.5 The values stated in SI units are to be regarded asstandard. No other units of measurement are included in thisstandard.1.6 This standard does not purport to address al
13、l of thesafety concerns, if any, associated with 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 requirements prior to use.NOTE 1There is no known ISO equivalent to this standard.1This
14、guide is under the jurisdiction of ASTM Committee D20 on Plastics andis the direct responsibility of Subcommittee D20.96 on Environmentally DegradablePlastics and Biobased Products.Current edition approved April 1, 2013. Published April 2013. Originallyapproved in 2004. Last previous edition approve
15、d in 2004 as D7026 - 04, which waswithdrawn January 2013 and reinstated with revisions in April 2013. DOI:10.1520/D7026-13.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12. Referenced Documents2.1 ASTM Standards:2D6852 Guide for Dete
16、rmination of Biobased Content, Re-sources Consumption, and Environmental Profile of Ma-terials and Products (Withdrawn 2011)3D6866 Test Methods for Determining the Biobased Contentof Solid, Liquid, and Gaseous Samples Using Radiocar-bon AnalysisE105 Practice for Probability Sampling of MaterialsE122
17、 Practice for Calculating Sample Size to Estimate, WithSpecified Precision, the Average for a Characteristic of aLot or Process2.2 Other Reference:Cramer, H., “Elements of Probability Theory,” Wiley that is, the degree ofcertainty of correctness of the estimate. Some k-valuesand the corresponding le
18、vels of uncertainty are pre-sented in Practice E122,k = 1.64 for 10 % chance of the error exceeding E,k = 2 for 5.5 % chance of the error exceeding E, andk = 3 for 0.3 % chance (practical certainty).6.3.1 These numbers are derived from the properties of therandom distribution curve.NOTE 2Following e
19、xamples use hypothetical values for sigma(0).They do not represent the values for the two analytical methods describedin Test Methods D6866, for which the sigma(0) are not yet available.6.4 Example Isigma(0) is 5 %.The expected biobased content is 50 %.It is desired to establish with 90 % certainty
20、that thebiobased content is greater than 45 %.Thus:E =5045=5k = 1.64n = (1.64 5/5)2=2.69=36.4.1 That means that the average of 3 samples must be atleast 50 % to state with 90 % assurance that the samplebiobased content is 45 % or greater. If the average of thesamples is less than 50 %, then the effe
21、ctive E is less and thenumber of samples must be increased until the criteria specifiedby the above formula are met.6.5 Example IILet sigma(0) = 5 %.E =2%.It is desired to state with 95 % assurance that the true meandoes not lie outside of E from the measured average.Hence:k = 2 (rounded off; true u
22、ncertainty is 5.5 %)n(95 %) = (2 5/2)2=256.5.1 The above illustrates the rapid increase in number ofsamples required as the E decreases and/or need for assuranceincreases. Obviously, it would be worthwhile to seek aninstrument with smaller sigma(0). The effects of decreasedvariability are shown in e
23、xample below.6.6 Example IIILet:E =1%k =2%sigma(0) = 2 %n(95 %) = (2 1/1)2= 4 samples6.6.1 Thus, the required number of samples is decreasedfrom 25 to 4, or roughly by a factor of 6.6.7 It is recommended that at least three samples be taken,even if the theoretical accuracy does not require that many
24、, toverify that the underlying assumptions about the material andsampling are valid. For example, a spread of 10 units betweentwo samples in Example III would be highly suspicious. Sucha spread would be possible, but not probable. In this caseadditional sampling would be appropriate.6.8 If E is grea
25、ter than 2 sigma(0), one can assumeuncertainty in the answer is not a problem. Thus the number ofsamples would be controlled by 3.14.7. Sample Preparation7.1 Sample preparation is discussed inTest Methods D6866,Section 8 for LSC and Section 12 for AMS.7.2 Size reduction of the particles of initial s
26、ample is oftenrequired so that a final, smaller sample can be obtained that isstill representative of the initial sample. This is especially truefor the AMS method due to the smaller sample size.7.3 The recommended procedure for the size reduction ofpliable materials (for example, many plastics) is
27、cryogenicgrinding. The grinding should be done with liquid N2cooling.Liquid or dry CO2should be avoided to prevent contaminationof sample with extraneous carbon.7.4 The final particle size should be 250 m or less.7.5 Powdered or granular materials must be well mixed dueto possible segregation of par
28、ticles by density.7.6 Transfer of sample after weighing should be avoided, ifat all possible. The ultimate destination of the sample is theD7026 133combustion tube, where the carbon is converted to CO2.Ifatall possible, the tube should be tared and the weight of thesample obtained as difference from
29、 the tare weight and finalweight of the tube.8. Special Considerations for Liquids8.1 All liquids should be either single phase or relativelystable emulsions (such as latex paints) which can be stirred andsampled without significant settling of the particles in theinterim. Any turbidity should be re
30、moved by centrifuging andthe clear liquid and the sediment examined separately. In caseof viscous liquids or materials with volatile components thetransfer problems make accurate weighing of the sample muchmore difficult. Effort should be made to obtain the sampleweight in the combustion tube, rathe
31、r than transferring apreviously weighed sample to the oxidation tube.9. Chain of Custody9.1 Any sample of a material that is being used for authen-tication of biobased content should be accompanied by a chainof custody sheet. Each individual handling the sample shouldmark his/her possession time and
32、 transfer to the next person.All mailings of the samples should be done in containers withinitialed seal, to be broken by the recipient and so noted in thecustody sheet.10. Report10.1 It is essential that the reporting include all phases of thesample acquisition and handling. This guide provides muc
33、hflexibility in the specific procedures used, provided the proce-dure is fully and clearly documented.10.2 The report must include the following:10.2.1 Description of material: morphology, other salientfeatures of the material,10.2.2 Basis for choice of the subunit or lot to be tested,10.2.3 Rationa
34、le for choice of sampling plan, includingreason for not using a random sampling plan,10.2.4 Method of sample collection,10.2.5 Drying and storing operations,10.2.6 Size reduction methods,10.2.7 Final sample weighing,10.2.8 Equipment used to perform radioisotope measure-ments: type, location, establi
35、shed sigma(0),10.2.9 Analytical results for each sample (as “percent mod-ern carbon (pMC) with one relative standard deviation),10.2.10 Reason for discarding a sample, if applicable,10.2.11 Chain of custody sheet, and10.2.12 Version of ASTM D6866 represented.11. Precision and Bias11.1 The precision
36、and bias of the radioisotope methods arediscussed in Test Methods D6866.11.2 The weighing accuracy is to be 1 mg for both the LSCand the AMS methods.11.3 Provided that proper procedures are followed, sam-pling should contribute minimally to the ultimate error inestimation of biobased content.12. Key
37、words12.1 biobased; radioisotope authentication; samplingASTM 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 determination of the validity of any such paten
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