ASTM D8473-22

Standard Test Method for Determining the Biobased content of Liquid Hydrocarbon Fuels Using Liquid Scintillation Counting with Spiked Carbon-14

SIGNIFICANCE AND USE
5.1 This test method provides accurate biobased/biogenic carbon content results to materials whose carbon source was directly in equilibrium with CO2 in the atmosphere at the time of cessation of respiration or metabolism, such as the harvesting of a crop or grass living in a field. Special considerations are needed to apply the testing method to materials originating from within artificial environments with non-natural levels of 14C or if the biofeed was grown over the course of several years such as trees and contains “bomb-carbon.” Application of these test methods to materials derived from CO2 uptake within artificial environments is beyond the present scope of this standard.  
5.2 This method uses LSC techniques to quantify the biobased content of a liquid hydrocarbon fuels using sample carbon that has been unmodified. It is designed to be able to incorporate into a refinery laboratory to support biofeed and petroleum coprocessing or blending operations to determine the biocarbon content of the intermediate or finished products. The test results can then be used for optimizing internal parameters or reporting to regulatory agencies.  
5.3 The use of this method requires that a pure petroleum-based sample can be generated that has a similar matrix to each product or stream to be analyzed. For example, gasoline and diesel have very different matrices and will likely require the use of different background measurements for each. Refer to 10.2 for how to determine if the same background sample can be used for more than one product/stream.
SCOPE
1.1 This test method covers quantitatively determining biocarbon content of liquid hydrocarbon fuels with a focus on those produced in a typical petroleum refinery using liquid scintillation counting (LSC). The method is designed to generate analogous results as Test Method D6866 Method C, for low quench samples, without the need of benzene synthesis. The purpose is to be able to use the produced data to report biocarbon content of refinery products to regulatory agencies and monitor refinery operation. The method does not address regulatory reporting or fuel performance.  
1.2 The method is needed to support refinery operations when bio-feeds are co-processed with petroleum within a reactor with a focus on samples with 100 % biocarbon or less (not for 14C labeled species). It allows refineries to report the biocarbon content of refinery products to regulatory agencies such as the Environmental Protection Agency (EPA) or California Air Resources Board (CARB) to comply with regulatory statutes such as The Renewable Fuel Standard (RFS) or Low Carbon Fuel Standard (LCFS).  
1.3 This test method is applicable to any liquid fuel product, petroleum based (pure hydrocarbon), biobased (such as renewable diesel or those that can contain oxygenates such as ethanol), or blends, that contain 1 % to 100 % by mass biocarbon where an instrument background can be experimentally determined using a sample of similar matrix that contains no measurable carbon-14.  
1.4 This test method makes no attempt to teach the basic principles of the instrumentation used although minimum requirements for instrument selection are referenced in Refs (1-11).2 However, the preparation of samples for the above test methods is described. No details of instrument operation are included here. These are best obtained from the manufacturer of the specific instrument in use.  
1.5 Pre-Requisite Requirements For Method Execution—This test method uses artificial carbon-14 (14C) within the method. Great care shall be taken to prevent laboratory contamination of the elevated 14C. Once in the laboratory, artificial 14C can contaminate a variety of laboratory surfaces that can lead to artificially high sample biocarbon measurements. If vigorous cleaning attempts to remove the artificial 14C from a laboratory are unsuccessful, instrumentation and sample preparation may have to be moved to a ne...

General Information

• Status: Published
• Publication Date: 14-Sep-2022
• ICS: 75.160.20 - Liquid fuels
• Technical Committee: D02 - Petroleum Products, Liquid Fuels, and Lubricants
• Drafting Committee: D02.04.0F - Absorption Spectroscopic Methods

Relations

• Refers: ASTM D6708-24 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Mar-2024
• Refers: ASTM D6300-24 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Mar-2024
• Refers: ASTM D6866-24 - Standard Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis
• Effective Date: 01-Feb-2024
• Refers: ASTM D6299-23a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Dec-2023
• Refers: ASTM D6300-23a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products, Liquid Fuels, and Lubricants
• Effective Date: 01-Dec-2023
• Refers: ASTM D6300-19a - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Dec-2019
• Refers: ASTM D6708-19 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-May-2019
• Refers: ASTM D6708-18 - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Apr-2018
• Refers: ASTM D6866-18 - Standard Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis
• Effective Date: 01-Mar-2018
• Refers: ASTM D6299-17b - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Dec-2017
• Refers: ASTM D6299-17a - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 15-Nov-2017
• Refers: ASTM D6299-17 - Standard Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance
• Effective Date: 01-Jan-2017
• Refers: ASTM D6866-16 - Standard Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis
• Effective Date: 01-Jun-2016
• Refers: ASTM D6708-16a - Standard Practice for Statistical Assessment and Improvement of Expected Agreement Between Two Test Methods that Purport to Measure the Same Property of a Material
• Effective Date: 01-Apr-2016
• Refers: ASTM D6300-16 - Standard Practice for Determination of Precision and Bias Data for Use in Test Methods for Petroleum Products and Lubricants
• Effective Date: 01-Apr-2016

Overview

ASTM D8473-22, titled Standard Test Method for Determining the Biobased Content of Liquid Hydrocarbon Fuels Using Liquid Scintillation Counting with Spiked Carbon-14, provides an internationally recognized method to quantify the biobased, or “biogenic,” carbon content in liquid hydrocarbon fuels. Developed by ASTM, this test is designed primarily for fuels and blends processed in petroleum refineries and supports the growing need for accurate renewable content verification in the energy sector.

This standard leverages Liquid Scintillation Counting (LSC) using spiked Carbon-14 to determine the proportion of renewable, non-fossil carbon in samples ranging from 1% to 100% biocarbon by mass. The results are essential for compliance reporting with regulatory programs such as the Renewable Fuel Standard (RFS) and Low Carbon Fuel Standard (LCFS), and for optimizing refinery bio-feed co-processing and blending operations.

Key Topics

• Scope and Applicability: ASTM D8473-22 applies to a diverse array of liquid hydrocarbon products, including pure petroleum fuels, renewable diesel, bio-based oxygenate blends, and mixtures containing any percentage of biocarbon.
• Measurement Principle: The test uses Liquid Scintillation Counting (LSC) to detect Carbon-14 in the sample. A spiked Carbon-14 internal standard determines counting efficiency, avoiding the need for benzene synthesis used in some legacy tests.
• Sample Matrix Considerations: The method requires the preparation of background samples for each distinct product or process stream due to the varying impact of different matrices such as gasoline and diesel on measurement accuracy.
• Quality Assurance: Laboratory control measures are emphasized to avoid contamination with artificial Carbon-14, which could lead to inaccurate results. Required precautions include using separate spaces, dedicated equipment, and regular wipe tests.
• Reporting and Use: The data generated allows refineries and related entities to substantiate claims of biobased content, comply with regulatory demands, and continuously improve operational efficiency.

Applications

ASTM D8473-22 is critical wherever precise determination of renewable carbon content is required in the petroleum and biofuel industries. Key applications include:

• Regulatory Reporting: Supports compliance with renewable energy regulations by quantifying the biobased fraction in refinery streams for agencies such as the EPA and CARB.
• Refinery Operations: Enables real-time monitoring and optimization of bio-feedstock integration with petroleum feedstock during co-processing and blending.
• Quality Control: Refineries and laboratories can routinely verify the renewable content in fuels to ensure adherence to internal specifications and sustainability goals.
• Product Certification: Producers of blended fuels and renewable fuels can substantiate claims regarding the proportion of biogenic carbon in their products, supporting environmental marketing and certification programs.

Related Standards

For a comprehensive approach to bio-based content measurement and quality assurance in fuels, the following related standards are often referenced alongside ASTM D8473-22:

• ASTM D6866 – Test Methods for Determining the Biobased Content of Solid, Liquid, and Gaseous Samples Using Radiocarbon Analysis.
• DIN 51637 – Liquid Petroleum Products – Determination of the Bio-Based Hydrocarbon Content in Diesel Fuels and Middle Distillates Using Liquid Scintillation Method.
• EN 16640 – Bio-based products – Determination of the Bio-Based Carbon Content using the Radiocarbon Method.
• ASTM D5291, D6299, D6300, D6708 – Methods supporting instrumental determinations and quality control in petroleum product testing.

Conclusion

ASTM D8473-22 is an essential standard for accurately determining the biobased carbon content in liquid hydrocarbon fuels. By supporting clear, reproducible measurements using sophisticated radiocarbon analysis, it drives transparency in renewable fuel production, regulatory reporting, and sustainable operations across the petroleum and biofuels industries. Laboratories and refineries adopting this method gain a reliable tool for both internal process optimization and external compliance in today’s evolving energy marketplace.

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: D8473 − 22
Standard Test Method for
Determining the Biobased content of Liquid Hydrocarbon
Fuels Using Liquid Scintillation Counting with Spiked
Carbon-14
This standard is issued under the fixed designation D8473; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope included here. These are best obtained from the manufacturer
of the specific instrument in use.
1.1 This test method covers quantitatively determining bio-
carbon content of liquid hydrocarbon fuels with a focus on
1.5 Pre-Requisite Requirements For Method Execution—
those produced in a typical petroleum refinery using liquid
This test method uses artificial carbon-14 ( C) within the
scintillation counting (LSC). The method is designed to gen-
method. Great care shall be taken to prevent laboratory
erate analogous results as Test Method D6866 Method C, for
contamination of the elevated C. Once in the laboratory,
low quench samples, without the need of benzene synthesis.
artificial C can contaminate a variety of laboratory surfaces
The purpose is to be able to use the produced data to report
that can lead to artificially high sample biocarbon measure-
biocarbon content of refinery products to regulatory agencies
ments. If vigorous cleaning attempts to remove the artificial
and monitor refinery operation. The method does not address 14
C from a laboratory are unsuccessful, instrumentation and
regulatory reporting or fuel performance.
sample preparation may have to be moved to a new laboratory
1.2 The method is needed to support refinery operations away from the contamination or the laboratory may have to
when bio-feeds are co-processed with petroleum within a
rely on outside third-party labs for analysis. Specific proce-
reactor with a focus on samples with 100% biocarbon or less dural steps have been incorporated into this method that
(not for C labeled species). It allows refineries to report the
minimize the risk of sample and lab contamination. Wipe tests
biocarbon content of refinery products to regulatory agencies
and quality assurance samples can validate absence of con-
such as the Environmental Protection Agency (EPA) or Cali-
tamination. In the event of contamination in the laboratory or
forniaAirResourcesBoard(CARB)tocomplywithregulatory
instrument, vigorous cleaning protocols shall be implemented,
statutes such as The Renewable Fuel Standard (RFS) or Low
andanalysiscannotberesumeduntilthelabandinstrumentare
Carbon Fuel Standard (LCFS).
free of contamination. Accepted requirements are:
1.3 Thistestmethodisapplicabletoanyliquidfuelproduct, 1.5.1 Working with the elevated C samples in a separate
petroleumbased(purehydrocarbon),biobased(suchasrenew- and defined area away from the instrument and the preparation
able diesel or those that can contain oxygenates such as of any non-spiked samples.
ethanol), or blends, that contain 1% to 100% by mass
1.5.2 Using separate personnel to prepare the spiked
biocarbon where an instrument background can be experimen-
samples and non-spiked samples.
tally determined using a sample of similar matrix that contains
1.5.3 Using separate laboratory spaces with separate HVAC
no measurable carbon-14.
systems for the handling of spiked and non-spiked samples.
1.4 This test method makes no attempt to teach the basic
The use of separate fume hoods that have separate exhaust
principles of the instrumentation used although minimum
ventilation satisfies this requirement.
requirements for instrument selection are referenced in Refs
1.5.4 Weekly wipe tests of C sample handling area(s) to
(1-11). However,thepreparationofsamplesfortheabovetest
detect lab contamination.
methods is described. No details of instrument operation are
1.6 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 appro-
This test method is under the jurisdiction of ASTM Committee D02 on
priate safety, health, and environmental practices and deter-
Petroleum Products, Liquid Fuels, and Lubricants and is the direct responsibility of
mine the applicability of regulatory limitations prior to use.
Subcommittee D02.04.0F on Absorption Spectroscopic Methods.
Current edition approved Sept. 15, 2022. Published October 2022. DOI:
1.7 This international standard was developed in accor-
10.1520/D8473-22.
2 dance with internationally recognized principles on standard-
The boldface numbers in parentheses refer to a list of references at the end of
this standard. ization established in the Decision on Principles for the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D8473 − 22
Development of International Standards, Guides and Recom- 3.2.5 biofeed, n—a feedstock sourced from a plant or
mendations issued by the World Trade Organization Technical animal.
Barriers to Trade (TBT) Committee.
3.2.6 biogenic, adj—containing carbon (organic and inor-
ganic) of renewable origin like agricultural, plant, animal,
2. Referenced Documents
fungi, microorganisms, marine, or forestry materials.
2.1 ASTM Standards:
3.2.7 biogenic carbon content, n—amount of biogenic car-
D5291Test Methods for Instrumental Determination of
bon in the material or product as a percent of the total carbon
Carbon, Hydrogen, and Nitrogen in Petroleum Products
(TC) in the product.
and Lubricants
3.2.8 carbon-14 ( C), n—naturally occurring radioactive
D6299Practice for Applying Statistical Quality Assurance
isotope of carbon that contains six protons and eight neutrons
and Control Charting Techniques to Evaluate Analytical
with a true half-life of 5730 years.
Measurement System Performance
D6300Practice for Determination of Precision and Bias
3.2.9 cocktail, n—the solution in which samples are mixed
Data for Use in Test Methods for Petroleum Products,
for measurement in an LSC.
Liquid Fuels, and Lubricants
3.2.10 coincidence circuit, n—a portion of the electronic
D6708Practice for StatisticalAssessment and Improvement
analysis system of an LSC which acts to reject pulses that are
of Expected Agreement Between Two Test Methods that
not received from the two or three photomultiplier tubes (that
Purport to Measure the Same Property of a Material
count the photons) within a given period of time and are
D6866Test Methods for Determining the Biobased Content
necessary to rule out background interference and required for
of Solid, Liquid, and Gaseous Samples Using Radiocar-
any LSC used in this test method.
bon Analysis
3.2.11 coincidence threshold, n—the minimum decay en-
2.2 Other Standards:
ergy required for an LSC to detect a radioactive event; the
DIN 51637Liquid Petroleum Products – Determination of
ability to set that threshold is a requirement of any LSC used
the Bio-Based Hydrocarbon Content in Diesel Fuels and
in this test method.
Middle Distillates Using Liquid Scintillation Method
CSN EN 16640 Bio-based products - Bio-based carbon
3.2.12 coincidence time, n—the time period used by the
content - Determination of the Bio-Based Carbon Content
coincidencecircuitthatisusedtodetermineifadetectionevent
using the Radiocarbon Method
is counted or rejected.
3.2.13 contemporary carbon, n—a direct indication of the
3. Terminology
relative contributions of fossil carbon and “living” biospheric
3.1 The definitions of terms used in this test method are
carbon can be expressed as the fraction (or percentage) of
referenced in case the practitioner requires further information
contemporarycarbon,symbolf ;thisisderivedfrom“fraction
C
regarding the practice of the art of isotope analysis and to
of modern” (f ) using the observed input function for atmo-
M
facilitate performance of these test methods.
spheric C over recent decades, representing the combined
3.2 Definitions:
effects of fossil dilution of C (minor) and nuclear testing
3.2.1 background radiation, n—the radiation in the natural
enhancement (major); the relation between f and f is
C M
environment; this includes cosmic radiation and radionucle-
necessarily a function of time; by 1985, when the particulate
otides present in the local environment, for example, materials
sampling discussed in the cited reference was performed, the
of construction, metals, glass, and concrete.
f ratio had decreased to approximately 1.2 (10, 11).
M
3.2.2 background sample, n—samplewithnodetectable C
3.2.14 counting time, n—the total time used by the liquid
(such as a carboniferous sample that should not contain any
scintillation counter to count sample C decays.
measurable C because of its geologic age).
3.2.15 counts per minute (cpm), n—the average number of
3.2.3 biobased, adj—containing organic carbon of renew-
counts the liquid scintillation counter detections during analy-
able origin like agricultural, plant, animal, fungi,
sis; is used to derive dpm.
microorganisms, marine, or forestry materials living in a
3.2.16 decay (radioactive), n—the spontaneous transforma-
natural environment in equilibrium with the atmosphere.
tion of one nuclide into a different nuclide or into a different
3.2.4 biobased carbon content, n—the amount of biobased
energy state of the same nuclide; the process results in a
carbon in the material or product as a percent of the total
decrease, with time, of the number of original radioactive
organic carbon (TOC) in the product.
atoms in a sample, according to the half-life of the radionu-
clide.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.2.17 delay time, n—the time the instrument waits after
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
method is started before it starts counting; allows user to delay
Standards volume information, refer to the standard’s Document Summary page on
thestartofanalysistoallowsamplephotoluminescencetostop
the ASTM website.
Available from Deutsches Institut für Normung e.V. (DIN), Am DIN-Platz, before counting is initiated.
Burggrafenstrasse 6, 10787 Berlin, Germany, http://www.din.de.
3.2.18 discriminator, n—an electronic circuit which distin-
Available from European Standards, Krimicka 134, 318 00 Pilsen, Czech
Republic, VAT: CZ09567909, https://www.en-standard.eu/. guishessignalpulsesaccordingtotheirpulseheightorenergy;
D8473 − 22
used to exclude extraneous radiation, background radiation, 3.2.32 pulse, n—the electrical signal result in when photos
and extraneous noise from the desired signal. are detected by the PMTs.
3.2.19 disintegrations per minute (dpm), n—the quantity of 3.2.33 quenching, n—any material that interferes with the
radioactivity; the measure dpm is derived from cpm or counts (accurate) optimal conversion of decay energy to scintillation
per minute (dpm = (cpm – cpm of background) / counting photons captured by the PMT of the LSC (a significant
interference with this test method).
efficiency); there are 2.2 × 10 dpm / µCi.
3.2.33.1 chemical quenching, n—a reduction in the scintil-
3.2.20 effıciency, n—the ratio of measured observations or
lationintensityseenbythePMTduetothematerialspresentin
counts compared to the number of decay events which oc-
the sample that interfere with the processes leading to the
curred during the measurement time; expressed as a percent-
production of light.
age.
3.2.33.2 color quenching, n—any material that absorbs
3.2.21 figures of merit, n—a term applied to a numerical
generated scintillation photons.
value used to characterize the performance of a system; in
liquid scintillation counting, specific formulas have been
3.2.34 region, n—regions of interest, also called window or
derived for quantitatively comparing certain aspects of instru-
channel, or both, regarding LSC; refers to an energy level or
ment and cocktail performance and the term is frequently used
subset specific to a particular isotope.
tocompareefficiencyandbackgroundmeasures(refertoEq1).
3.2.35 renewable, n—being readily replaced and of non-
3.2.22 fluorescence, n—the emission of light resulting from
fossil origin; specifically, not of petroleum origin.
the absorption of incident radiation and persisting only as long
3.2.36 scintillation, n—the sum of all photons produced by
as the stimulation radiation is continued.
a radioactive decay event; counters used to measure this as
3.2.23 fossil carbon, n—carbonthatcontainsnomeasurable
described in this test method are Liquid Scintillation Counters
radiocarbon because its age is very much greater than the
(LSC).
5730-year true half-life of C.
3.2.37 scintillation reagent, n—chemicals that absorbs de-
3.2.24 half-life, n—the time in which one half the atoms of
cay energy transferred from the solvent and emits light
a particular radioactive substance disintegrate to another
(photons) proportional in intensity to the decay energy.
nuclear form; the true half-life of C is 5730 years.
3.2.38 solvents and scintillators, n—chemicals that absorb
3.2.25 intensity, n—the amount of energy, the number of
decay energy transferred from the solvent and emits light
photons, or the numbers of particles of any radiation incident (photons) proportional in intensity to the deposited energy.
upon a unit area per unit time.
3.2.39 solvent-in scintillation reagent, n—chemical(s)
3.2.26 internal standard, n—a known amount of radioactiv- which act as both a vehicle for dissolving the sample and
ity which is added to a sample to determine the counting
scintillatorandthelocationoftheinitialkineticenergytransfer
efficiency of that sample; the radionuclide used shall be the from the decay products to the scintillator; that is, into
same as that in the sample to be measured and have a certified
excitation energy that can be converted by the scintillator into
activity. photons.
3.2.27 luminescence, n—scintillation flux of photons; can
3.2.40 specific activity (SA), n—refers to the quantity of
produce coincidences if intense; causes—luminescent reac- radioactivity per mass unit of product, that is, decays per
tionsinsample,photoluminescencefrombright,especiallyUV
minute per gram of carbon (dpm/gC).
excitation.
3.2.41 standard count conditions (STDCT), n—LSC condi-
tions under which reference standards and samples are
3.2.28 modern carbon, n—explicitly, 0.95 times the specific
activity of SRM 4990B (the original oxalic acid radiocarbon counted.
standard), normalized to δ C = −19% (10); functionally, the
3.2.42 triple to double count ratio (TDCR), n—the ratio of
fraction of modern carbon equals 0.95 times the concentration
counts detected by three detectors over the number of counts
of C contemporaneous with 1950 wood (that is, pre-
that were detected by two detectors; requires use of a liquid
atmosphericnucleartesting).Tocorrectforthepost1950bomb
scintillation counter with three detectors.
C injection into the atmosphere, the fraction of modern
3.2.43 wipe test, n—a test that is done to determine if a
carbon is multiplied by a (REF) atmospheric adjustment value
14 surface has been contaminated with C or any other radioac-
representative of the excess C in the atmosphere at the time
tive isotope.
of measurements.
3.2.29 noise pulse, n—a spurious signal arising from the
4. Summary of Test Method
electronic and electrical supply of the instrument.
4.1 Fuels or their component streams, or both, are mixed
3.2.30 operational quality test (OQ), n—test done to verify
with scintillation cocktail and placed into a liquid scintillation
liquid scintillation counter is working properly.
counterwithTDCRcapabilities.Theinstrumentisthenusedto
3.2.31 photomultiplier tube (PMT, pmt), n—the device in determine the number of C disintegrations per minute per
the LSC that counts the photons of light simultaneously at two gram of carbon in the sample to calculate its biological carbon
or three separate detectors. content. C spiking using a separate aliquot of the same
D8473 − 22
sample, and prepared at a different location, is used to amplitude luminescence pulses, and employ delay time before
determine counting efficiencies of each sample. counting starts, to allow photoluminescence to fade.
6.4 Sample and scintillation cocktail volumes need to be
5. Significance and Use
consistent to obtain accurate efficiency measurements. Varia-
5.1 This test method provides accurate biobased/biogenic tions in the sample to cocktail ratio will change the dilution of
carbon content results to materials whose carbon source was
the quenching agents present in the sample resulting in an
directly in equilibrium with CO in the atmosphere at the time increase or decrease in counting efficiency if too little sample
of cessation of respiration or metabolism, such as the harvest-
or too much sample is added in respect to the scintillation
ing of a crop or grass living in a field. Special considerations cocktail, respectively. Measured volumes shall not fluctuate
are needed to apply the testing method to materials originating
more than 0.1mL from the target volume to ensure data
from within artificial environments with non-natural levels of accuracy.
C or if the biofeed was grown over the course of several
6.5 Biological carbon contamination from outside sources,
yearssuchastreesandcontains“bomb-carbon.”Applicationof
sourcesoffossilormoderncarbonsuchascorks,papertowels,
thesetestmethodstomaterialsderivedfromCO uptakewithin
plant-based rope/string or dust shall be kept away from the
artificial environments is beyond the present scope of this
samples to prevent contamination of the sample.
standard.
6.6 C Spike Standard Contamination in Samples—
5.2 This method uses LSC techniques to quantify the
Precaution is needed when preparing and handling the spike
biobased content of a liquid hydrocarbon fuels using sample
solution and spiked samples to prevent sample and laboratory
carbon that has been unmodified. It is designed to be able to
contamination. Review 1.5 to make sure all necessary precau-
incorporate into a refinery laboratory to support biofeed and
tions are being followed.
petroleum coprocessing or blending operations to determine
6.7 Sample Volatility—Addition of the sample to the vial
the biocarbon content of the intermediate or finished products.
should always be the last step. When samples are weighed, a
The test results can then be used for optimizing internal
cap needs to be tightly sealed when recording the final sample
parameters or reporting to regulatory agencies.
mass measurement and the cap should not be reopened before
5.3 The use of this method requires that a pure petroleum-
measuring. Background samples that are collected and stored
basedsamplecanbegeneratedthathasasimilarmatrixtoeach
for extended periods of time shall be stored and sampled in a
product or stream to be analyzed. For example, gasoline and
manner to prevent loss of volatiles.
diesel have very different matrices and will likely require the 40
6.8 Potassium-40 ( K)—Aradioactiveisotopeofpotassium
use of different background measurements for each. Refer to
thatispresentinglassware. Kpredominantlydecaysthrough
10.2 for how to determine if the same background sample can 40 40
beta decay to Ca. The beta decay LSC spectrum of K
be used for more than one product/stream.
partially overlaps with that of C. Even low potassium glass
still has high enough levels of K to interfere with the results
6. Interferences
producedviathismethod.Forthisreason,thismethodrequires
6.1 Sample Matrix—The sample matrix affects background
the use of PTFE coated plastic vials and not glass vials to
and quenching, so backgrounds (samples with no detectable
prevent this interference.
C) need to be measured for each stream or blend that is to be
6.9 Radon-222, see 14.4 for how to correct for radon
analyzed.
contamination.
6.2 Chemical/Color Quenching—Higher boiling samples
6.10 Bomb Pulse:
will likely contain higher levels of quenching molecules such
6.10.1 The pMC can be greater than 100% because of the
as conjugated aromatics.The presence of these species in high
continuing but diminishing effects of the 1950s nuclear testing
concentrations can require sample dilutions or prevent use of 14
programs, which resulted in a considerable enrichment of C
this method. Counting efficiency measurements can be con- 14
in the atmosphere. The decrease in C from the bomb testing
ductedtodetermineifthequenchlevelsaretoohigh.Counting
programs has been nonlinear in the past but has been linear
efficiency is required to be above 50.0%. 14
sinceatleast2004topresent.Asof2019the Cactivityinthe
6.3 Luminescence—In LSC context, unwanted non-
atmosphere has reached the 1950 level of 13.56dpm per gram
scintillation flux of photons. Consists of single photons and, if carbon that is defined as 100pMC. Because all sample C
moderate, does not markedly produce coincidences. If lumi- activities are referenced to a “prebomb” standard, and because
nescence intensity increases, probability for two photons hit- nearly all new biobased products are produced in a post-bomb
ting separate PMT’s within coincidence time increases and environment, all pMC values shall be adjusted by an atmo-
random coincidences start to occur. Probability for triple spheric correction factor (REF) to obtain the true biobased
coincidences remains near negligible though. Common causes content of the sample. The correction factor is based on the
of luminescence are luminescent reactions in sample (chemi- excess or deficiency of C activity in the atmosphere at the
luminescence) and photon emission after exposure to light, timethebiologicalsourcewasalive.AREFvalueof102pMC
especially UV illumination (photoluminescence). Precautions wasdeterminedfor2015basedonthemeasurementsofCO in
to minimize luminescence include, avoid bright illumination air in a rural area in the Netherlands (Lutjewad, Groningen).
whenpreparingandhandlingsamples,selecttriplecoincidence The first version of Test Method D6866–04 in 2004 refer-
mode and/or set counting region (window) to exclude low- enced a value of 107.5pMC and the Test Method D6866–10
D8473 − 22
NOTE 1—Hidex 300 SL was used to conduct initial studies.
version (2010) cited 105pMC. These data points equate to a
decline of 0.5pMC per year. Therefore, on January 2 of each
7.2 Anti-coincidence systems with at least three PMTs
year, the values in Table 1 are used as REF through 2019,
(multidetector systems).
reflectingthesame0.5pMCdecreaseperyearuntil2019when
NOTE 2—Hidex brand LSC’s are currently the only known commercial
theprebombpulselevelwasreached.ForallREFvaluesafter
brand to have three detectors.
2022, refer to the most recent version of Test Method D6866.
7.3 Coincidence circuits.
6.10.2 Atmospheric thermonuclear weapons testing was
extensive between 1952 and 1963. During this time period the 7.4 Optimized counting regions to provide very low back-
CO content in the air increased by 90%. This means that a
ground counts while maintaining counting efficiency greater
plant living in 1965 would measure about 190pMC. Since the than 50.0%. The optimization of counting regions shall be
signing of the testing ban in 1963 this signature declined to
determined for each sample type to be analyzed. The level of
about 140pMC by 1975, 120pMC by 1985, and 101.5pMC quench for a given sample type will change the optimal region
by 2016. The consequence of this effect is error in biobased
of interest.
content analysis relating to when the biobased material used in
NOTE3—Initialworkfoundthatcountingoverchannels100to400was
the product was last actively part of a respiring/metabolizing
optimal for a diesel fuel sample.
system. The error is predominant in products made from
NOTE 4—Test Method D6866 Method C recommends an efficiency of
60% or higher. As that method is using a uniform and constant matrix
forestry products. The rings within trees each represent the
with little to no quenching present, this efficiency is more than adequate.
previous growth season within which the previous year’s
NOTE 5—This method analyzes the samples with no sample
CO signature was recorded. The center most ring of a tree
preparation,andtheanalysisofsampleswithhigherlevelsofquenchmay
living today but planted in 1965 would be about 190pMC
be needed, but as the level of quench increases, it is more difficult to
whereas the outermost ring/bark would be 100.0pMC. If this
distinguish low biocarbon containing samples from the noise. Depending
on the expected biocarbon concentration of the sample, it may be more
treeisharvestedandusedinmanufacturingabiobasedproduct,
beneficial to dilute the sample to increase the counting efficiency as
the percent biobased carbon content of the product will be
sample dilution increases efficiency proportionally higher than it reduces
dependent on where the carbon came from within the tree and
theamountofsampleused,thatis,a25%dilutionwillincreaseefficiency
would be the average pMC of each of the rings and their size
bymorethan25%forhighquenchsamples.Startrunningthesamplewith
in the portion of the tree used in the manufacturing process.
a small dilution first and slowly increasing the dilution factor until the
measured efficiency is over 50.0%. Some example dilutions ratios are
6.10.3 Bomb carbon is readily identified in a product when
suggested here (mLsample+mLcocktail): 12+8, 10+10, 8+12, 5+15, and
the product’s pMC value is greater than 6pMC above the
2+18. 13.5 describes how to proceed if dilution is required.
prescribed correction factor (REF). A high value can be
7.5 No single LSC is specified for this method. However,
predicted based on the origin of the manufacturing compo-
minimum counting efficiency and control of background inter-
nents. High values are typically observed in paper, cardboard,
ference is specified. Like all analytical instruments, LSCs
forestry products, and forestry-derived chemicals. An exact
require study as to their specific components and counting
correction factor REF is not possible based strictly on the
optimization. Currently Hidex is the only commercial source
measured pMC value of the product.
of a three PMT LSC system that satisfies need stated in 7.2.
6.11 Variationintransmittancefromvialtovial.EachPTFE
7.6 Standardization of sample preparation is required.
coated vial may have a slightly different transmittance through
it. As different vials are used to measure the background,
NOTE 6—Initial work used 15mL of sample with 5mL of scintillation
sample, and sample counting efficiency the variations in cocktail.
transmittancefromonevialtoanotherwillincreasetheerrorof
7.7 Unused20 mL sample vials comprised of PTFE coated
the calculated results.
plastic shall be used. Vials are not to be reused after sample
analysis.
7. Apparatus
NOTE 7—20mL PTFE coated plastic vials were used to keep back-
7.1 Low level LSCs with active shielding that can produce
ground levels as low as possible and allow for higher sample volumes to
consistent background counts for a given sample matrix.
decrease method detection limit.
7.8 The aforementioned optimizations shall be performed
TABLE 1 Percent Modern Carbon (pMC) Reference
usingasuitablereferencestandardusingthesamereagentsand
Year REF (pMC)
counting parameters as the samples. The reference standard
2015 102.0
used for optimization shall be similar to the samples to be
2016 101.5
2017 101.0
2018 100.5
The sole source of supply of the apparatus known to the committee at this time
2019 100.0
is HIDEX, Lemminkäisenkatu 62 FIN-20520 Turku, Finland. If you are aware of
2020 100.0
alternative suppliers, please provide this information to ASTM International
2021 100.0
2022 100.0 Headquarters.Your comments will receive careful consideration at a meeting of the
responsible technical committee, which you may attend.
D8473 − 22
analyzed. The standard should have low volatility and have a responsibility of the user of this test method to establish
similar matrix to that of the samples to be analyzed, that is, if appropriate safety and health practices. It is also incumbent on
thesamplesareexpectedtocontainoxygenatessuchasethanol the user to conform to all the government legislation for their
thestandardshouldalsocontainthesameoxygenatesinsimilar location, especially those that relate to the use of open
concentrations. radioactive source, in the performance of this test method.
Although C is one of the safest isotopes to work with, all
NOTE 8—Initial work used diesel samples to determine optimized
government regulations shall be followed in the performance
conditions as diesel is the most colored sample with the most complex
of this test method. As this method utilizes elevated levels of
matrix.
C additional regulations and precautions may apply.
7.9 Counting interference concerns that shall be addressed
as part of specific instrument calibration and normalization
10. Sampling, Test Specimens, and Test Units
include luminance, chemical or color quench, static electricity,
random noise, temperature, and humidity variability.
10.1 When sampling from large tanks avoid using compo-
nents that contain carbon-based material such as a cork or
7.10 Alternate regions of interest parameters may be used
non-synthetic rope or string. Metal or glass shall be used
based upon testing of 20, or more, 5h counts of the same
wherever possible when safe to do so.
reference standard that record the raw data throughout C
spectralregion(channels5to650forHidex instrumentation).
10.2 If this method is to be used to support coprocessing of
Optimal counting conditions shall be established by maximiz-
biofeedswithpetroleuminarefineryorsimilarsettingsamples
ing the Figures of Merit (see Eq 1) to obtain the highest count
shall be collected before coprocessing has started from each
efficiency and the lowest background. Counting efficiency of
stream or product, that will be analyzed after coprocessing has
less than 50.0% is unacceptable and can be improved by LSC
started to allow for adequate backgrounds to be measured.
instrument optimization and sample/reagent compatibility or
These samples serve as a background for the desired products/
shielding improvements.
streams and will allow for background corrections to be made.
FiguresofMerit 5 E 3 V ⁄ bkg 3 k (1)
~~ ! ! Onebackgroundwillhavetobepreparedandmeasuredweekly
(all other backgrounds on a monthly basis, measurement
where:
frequencyoutlinedinmoredetailin11.3.5)toverifylaboratory
E = counting efficiency, 14
is not contaminated with artificial C and to account for any
V = volume of sample,
instrumental drift, thus make sure enough sample is collected
bkg = CPM measured over a specific LSC channel range,
as it may be needed for several years. More volatile samples,
and
such as gasoline boiling range material, shall be stored in a
k = 1CPM/(%×mL) .
cold area to prevent loss of volatile components over a long
NOTE 9—Eq 1 is from DIN 51637.
period of time. The same background can be used for several
products/streams if the backgrounds of those products/streams
8. Reagents and Materials
have been experimentally determined to be indistinguishable.
8.1 Unused20mLPTFEcoatedplasticvials.Allvialsareto
Todetermineifbackgroundscanbeconsideredthesameornot
be single use to avoid sample carryover and reducing the risk usea t-testaftertenbackgroundmeasurementshavebeendone
of lab contamination from artificial C present in the spiked
and use the t-value for a 95% confidence interval.
samples.
10.3 Samples shall be thoroughly mixed before adding to
8.2 Unquenched standard kit used to verify instrument
the scintillation vial.
performance.
11. Calibration, Standardization, and Quality Control
8.3 Internal standard kit C, compatible with sample
matrix, used to determine counting efficiency of samples. (The
11.1 Apparatus—Operationalqualityoftheinstrumentshall
C labeled compound used to create the spike shall be a
be determined weekly to make sure the instrument is working
non-volatile compound (vapor pressure below 1Pa at 25°C)
properly. This can be done with an unquenched standard of
such as cholesterol to minimize potential of the compound 14
known C activity. Some commercial instruments hav
...