1、Designation: D6866 12Standard Test Methods forDetermining the Biobased Content of Solid, Liquid, andGaseous Samples Using Radiocarbon Analysis1This standard is issued under the fixed designation D6866; the number immediately following the designation indicates the year oforiginal adoption or, in the
2、 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.1. Scope*1.1 These test methods do not address environmental im-pact, product performance and funct
3、ionality, determination ofgeographical origin, or assignment of required amounts ofbiobased carbon necessary for compliance with federal laws.1.2 These test methods are applicable to any product con-taining carbon-based components that can be combusted in thepresence of oxygen to produce carbon diox
4、ide (CO2) gas. Theoverall analytical method is also applicable to gaseoussamples, including flue gases from electrical utility boilers andwaste incinerators.1.3 These test methods make no attempt to teach the basicprinciples of the instrumentation used although minimumrequirements for instrument sel
5、ection are referenced in theReferences section. However, the preparation of samples forthe above test methods is described. No details of instrumentoperation are included here. These are best obtained from themanufacturer of the specific instrument in use.1.4 Currently, there are no ISO test methods
6、 that areequivalent to the test methods outlined in this standard.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 establish appro-priate safety and health practices and determine the app
7、lica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D883 Terminology Relating to Plastics3. Terminology3.1 The definitions of terms used in these test methods arereferenced in order that the practitioner may require furtherinformation regarding the practice
8、of the art of isotope analysisand to facilitate performance of these test methods.3.2 Terminology D883 should be referenced for terminol-ogy relating to plastics. Although an attempt to list terms in alogical manner (alphabetically) will be made as some termsrequire definition of other terms to make
9、 sense.3.3 Definitions:3.3.1 dpmdisintegrations per minute. This is the quantityof radioactivity. The measure dpm is derived from cpm orcounts per minute (dpm = cpm bkgd / counting efficiency).There are 2.2 by 106dpm / uCi (14,17).33.3.2 dpsdisintegrations per second (rather than minute asabove) (14
10、,17).3.3.3 scintillationthe sum of all photons produced by aradioactive decay event. Counters used to measure this asdescribed in these test methods are Liquid Scintillation Coun-ters (LSC) (14,17).3.3.4 specific activity (SA)refers to the quantity of radio-activity per mass unit of product, that is
11、, dpm per gram (14,17).3.3.5 automated effciency control (AEC)a method usedby scintillation counters to compensate for the effect ofquenching on the sample spectrum (14).3.3.6 AMS facilitya facility performing Accelerator MassSpectrometry.3.3.7 accelerator mass spectrometry (AMS)an ultra-sensitive t
12、echnique that can be used for measuring naturallyoccurring radio nuclides, in which sample atoms are ionized,accelerated to high energies, separated on basis of momentum,charge, and mass, and individually counted in Faraday collec-tors. This high energy separation is extremely effective infiltering
13、out isobaric interferences, such thatAMS may be usedto measure accurately the14C/12C abundance to a level of 1 in1015. At these levels, uncertainties are based on countingstatistics through the Poisson distribution (8,9).3.3.8 background radiationthe radiation in the naturalenvironment; including co
14、smic radiation and radionuclidespresent in the local environment, for example, materials ofconstruction, metals, glass, concrete (2,4,7,8,14-19).1These test methods are under the jurisdiction of ASTM Committee D20 onPlastics and are the direct responsibility of Subcommittee D20.96 on Environmen-tall
15、y Degradable Plastics and Biobased Products.Current edition approved April 1, 2012. Published May 2012. Originallyapproved in 2004. Last previous edition approved in 2011 as D6866 - 11. DOI:10.1520/D6866-12.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer
16、 Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The boldface numbers in parentheses refer to the list of references at the end ofthis standard.1*A Summary of Changes section appears at the end of this
17、standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.3.9 biobased contentthe amount of biobased carbon inthe material or product as a percent of the weight (mass) of thetotal organic carbon in the product (1).3.3.10 coincidence
18、circuita portion of the electronicanalysis system of a Liquid Scintillation Counter which acts toreject pulses which are not received from the two Photomul-tiplier Tubes (that count the photons) within a given period oftime and are necessary to rule out background interference andrequired for any LS
19、C used in these test methods (7,14,17).3.3.11 coincidence thresholdthe minimum decay energyrequired for a Liquid Scintillation Counter to detect a radioac-tive event. The ability to set that threshold is a requirement ofany LSC used in these test methods (14,17).3.3.12 contemporary carbona direct in
20、dication of therelative contributions of fossil carbon and “living” biosphericcarbon can be expressed as the fraction (or percentage) ofcontemporary carbon, symbol fC. This is derived from fMthrough the use of the observed input function for atmo-spheric14C over recent decades, representing the comb
21、inedeffects of fossil dilution of14C (minor) and nuclear testingenhancement (major). The relation between fCand fMisnecessarily a function of time. By 1985, when the particulatesampling discussed in the cited reference the fMratio haddecreased to ca. 1.2 (8,9).3.3.13 chemical quenchinga reduction in
22、 the scintillationintensity (a significant interference with these test methods)seen by the Photomultiplier Tubes (PMT, pmt) due to thematerials present in the scintillation solution that interfere withthe processes leading to the production of light. The result isfewer photons counted and a lower e
23、fficiency (4,7,17).3.3.14 chi-square testa statistical tool used in radioactivecounting in order to compare the observed variations in repeatcounts of a radioactive sample with the variation predicted bystatistical theory. This determines whether two different distri-butions of photon measurements o
24、riginate from the samephotonic events. LSC instruments used in this measurementshould include this capability (14,17,27).3.3.15 cocktailthe solution in which samples are placedfor measurement in a LSC. Solvents and Scintillators (chemi-cals that absorbs decay energy transferred from the solvent ande
25、mits light (photons) proportional in intensity to the depositedenergy) (4,7,14,17).3.3.16 decay (radioactive)the spontaneous transforma-tion of one nuclide into a different nuclide or into a differentenergy state of the same nuclide. The process results in adecrease, with time, of the number of orig
26、inal radioactiveatoms in a sample, according to the half-life of the radionuclide(8,14,17).3.3.17 discriminatoran electronic circuit which distin-guishes signal pulses according to their pulse height or energy;used to exclude extraneous radiation, background radiation,and extraneous noise from the d
27、esired signal (14,17,18,32).3.3.18 effciencythe ratio of measured observations orcounts compared to the number of decay events which oc-curred during the measurement time; expressed as a percentage(14,17).3.3.19 external standarda radioactive source placed adja-cent to the liquid sample in to produc
28、e scintillations in thesample for the purpose of monitoring the samples level ofquenching (14,17).3.3.20 figure of merita term applied to a numerical valueused to characterize the performance of a system. In liquidscintillation counting, specific formulas have been derived forquantitatively comparin
29、g certain aspects of instrument andcocktail performance and the term is frequently used tocompare efficiency and background measures (14,17,20).3.3.21 fluorescencethe emission of light resulting fromthe absorption of incident radiation and persisting only as longas the stimulation radiation is conti
30、nued (14,17,25).3.3.22 fossil carboncarbon that contains essentially noradiocarbon because its age is very much greater than the 5730year half-life of14C (8,9).3.3.23 half-lifethe time in which one half the atoms of aparticular radioactive substance disintegrate to another nuclearform. The half-life
31、 of14C is 5730 years (8,14,25).3.3.24 intensitythe amount of energy, the number ofphotons, or the numbers of particles of any radiation incidentupon a unit area per unit time (14,17).3.3.25 internal standarda known amount of radioactivitywhich is added to a sample in order to determine the countinge
32、fficiency of that sample. The radionuclide used must be thesame as that in the sample to be measured, the cocktail shouldbe the same as the sample, and the Internal Standard must beof certified activity (14,17).3.3.26 modern carbonexplicitly, 0.95 times the specificactivity of SRM 4990b (the origina
33、l oxalic acid radiocarbonstandard), normalized to d13C = 19 % (Currie, et al., 1989).Functionally, the fraction of modern carbon equals 0.95 timesthe concentration of14C contemporaneous with 1950 wood(that is, pre-atmospheric nuclear testing). To correct for thepost 1950 bomb14C injection into the a
34、tmosphere (9), thefraction of modern carbon is multiplied by 0.95 (as of the year2010).3.3.27 noise pulsea spurious signal arising from theelectronics and electrical supply of the instrument(14,17,21,29).3.3.28 phase contactthe degree of contact between twophases of heterogeneous samples. In liquid
35、scintillation count-ing, better phase contact usually means higher counting effi-ciency (14,17).3.3.29 photomultiplier tube (PMT, pmt)the device in theLSC that counts the photons of light simultaneously at twoseparate detectors (29,32).3.3.30 pulsethe electrical signal resulting when photonsare dete
36、cted by the Photomultiplier tubes (14,17,18,32).3.3.31 pulse height analyzer (PHA)an electronic circuitwhich sorts and records pulses according to height or voltage(14,17,18,32).3.3.32 pulse indexthe number of afterpulses following adetected coincidence pulse (used in three dimensional or pulseheigh
37、t discrimination) to compensate for the background of aliquid scintillation counter performing (14,18,29,32).D6866 1223.3.33 quenchingany material that interferes with theaccurate conversion of decay energy to photons captured by thePMT of the LSC (2,4,7,14,15,17,20).3.3.34 regionregions of interest
38、, also called windowand/or channel in regard to liquid scintillation counters. Refersto an energy level or subset specific to a particular isotope(4,14,18,21,29).3.3.35 scintillation reagentchemicals that absorbs decayenergy transferred from the solvent and emits light (photons)proportional in inten
39、sity to the decay energy (4,14,29).3.3.36 solventin scintillation reagent, chemical(s) whichact as both a vehicle for dissolving the sample and scintillatorand the location of the initial kinetic energy transfer from thedecay products to the scintillator; that is, into excitation energythat can be c
40、onverted by the scintillator into photons(4.14,17,29).3.3.37 standard count conditions (STDCT)LSC condi-tions under which reference standards and samples arecounted.3.3.38 three dimensional spectrum analysisthe analysis ofthe pulse energy distribution in function of energy, counts perenergy, and pul
41、se index. It allows for auto-optimization of aliquid scintillation analyzer allowing maximum performance.Although different Manufacturers of LSC instruments callThree Dimensional Analysis by different names, the actualfunction is a necessary part of these test methods (14,17,18).3.3.39 true beta eve
42、ntan actual count which representsatomic decay rather than spurious interference (10,11).3.3.40 flexible tube crackerthe apparatus in which thesample tube (Break Seal Tube) is placed (5,6,10,11).3.3.41 break seal tubethe sample tube within which thesample, copper oxide, and silver wire is placed.4.
43、Significance and Use4.1 Presidential (Executive) Orders 13101, 13123, 13134,Public Laws (106-224), AG ACT 2003 and other LegislativeActions all require Federal Agencies to develop procedures toidentify, encourage and produce products derived frombiobased, renewable, sustainable and low environmental
44、 im-pact resources so as to promote the Market DevelopmentInfrastructure necessary to induce greater use of such resourcesin commercial, non food, products. Section 1501 of the EnergyPolicyAct of 2005 (Public Law 10958) and EPA40 CFR Part80 (Regulation of Fuels and Fuel Additives: Renewable FuelStan
45、dard Requirements for 2006) require petroleum distribu-tors to add renewable ethanol to domestically sold gasoline topromote the nations growing renewable economy, with re-quirements to identify and trace origin.4.2 Method B utilizes Accelerator Mass Spectrometry(AMS) along with Isotope Ratio Mass S
46、pectrometry (IRMS)techniques to quantify the biobased content of a given product.Intsrumental error can be within 0.1-0.5 % (1 rsd), but empiri-cal studies identify a total uncertainty up to 63 % (absolute)inclusive of indeterminant sources of error in the final biobasedcontent result. Sample prepar
47、ation methods include the pro-duction of CO2 within a vacuum manifold system where it isultimately distilled, quantified in a calibrated volume, trans-ferred to a quartz tube, and torch sealed. Details are given in8.7-8.10. The stored CO2is then delivered to an AMS facilityfor final processing and a
48、nalysis.4.3 Method C uses LSC techniques to quantify the biobasedcontent of a product using sample carbon that has beenconverted to benzene. This test method determines thebiobased content of a sample with a maximum total error of63 % (absolute), as does Method B.4.4 The test methods described here
49、directly discriminatebetween product carbon resulting from contemporary carboninput and that derived from fossil-based input. A measurementof a products14C/12C content is determined relative to themodern carbon-based oxalic acid radiocarbon Standard Refer-ence Material (SRM) 4990c, (referred to as HOxII). It iscompositionally related directly to the original oxalic acidradiocarbon standard SRM 4990b (referred to as HOxI), and isdenoted in terms of fM, that is, the samples fraction of moderncarbon. (See Terminology, Section 3.)4.5 Refe
