ASTM D7771-17a(2022)

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: D7771 − 17a (Reapproved 2022)
Standard Test Method for
Determination of Benzo-α-Pyrene (BaP) Content in Carbon
Black
This standard is issued under the fixed designation D7771; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2.2 EPA Standard:
Method 8270D Semivolatile Organic Compounds by Gas
1.1 This test method covers the qualitative and quantitative
Chromatography/Mass Spectrometry (GC/MS)
determination of only benzo-α-pyrene (BaP), a specific poly-
2.3 Federal Standard:
cyclic aromatic hydrocarbon (PAH), on carbon black. The
21 CFR 178.3297 Indirect Food Additives: Adjuvants, Pro-
procedure involves Soxhlet extraction with toluene and analy-
ductions Aids, and Sanitizers, Colorants for Polymers
sis by gas chromatography with mass spectrometry (GC/MS).
This method is not intended to test for U.S. Food and Drug
3. Terminology
Administration (FDA21 CFR 178.3297) compliance of carbon
3.1 Definitions of Terms Specific to This Standard:
blacks used for indirect food contact applications.
3.1.1 benzo-α-pyrene, BaP, n—also known as 3,4-
1.2 Units—The values stated in SI units are to be regarded
benzopyrene or benzo-a-pyrene is a specific polycyclic aro-
as the standard. No other units of measurement are included in
matic hydrocarbon (PAH) or polynuclear aromatic hydrocar-
this standard.
bon that consists of fused aromatic rings with no heteroatom or
substituent.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the 3.1.1.1 Discussion—PAHs naturally occur in oil, coal, and
tar deposits; are produced by the incomplete combustion of
responsibility of the user of this standard to establish appro-
hydrocarbons;andoccurinmanyotherproductsandprocesses.
priate safety, health, and environmental practices and deter-
BaP is a pentacyclic PAH with the formula C H , related to
mine the applicability of regulatory limitations prior to use.
20 12
pyrene by fusion of a phenylene group in the alpha position.
1.4 This international standard was developed in accor-
dance with internationally recognized principles on standard-
4. Summary of Test Method
ization established in the Decision on Principles for the
4.1 A portion of carbon black is Soxhlet-extracted with
Development of International Standards, Guides and Recom-
toluene for 16 h. The extract is concentrated and subsequently
mendations issued by the World Trade Organization Technical
analyzed for BaPby gas chromatography with mass spectrom-
Barriers to Trade (TBT) Committee.
etry (GC/MS). The BaP quantification is performed by the
2. Referenced Documents
means of an internal standard.
2.1 ASTM Standards:
5. Significance and Use
D4483 Practice for Evaluating Precision for Test Method
5.1 This test procedure is used to determine the concentra-
Standards in the Rubber and Carbon Black Manufacturing
tion of BaP extracted from carbon black by the means of a
Industries
Soxhlet extraction apparatus with toluene.
6. Apparatus
This test method is under the jurisdiction ofASTM Committee D24 on Carbon
Black and is the direct responsibility of Subcommittee D24.66 on Environment,
6.1 Soxhlet Extractor with Reflux Condenser, 50- or 100-
Health, and Safety.
cm capacity.
CurrenteditionapprovedJune1,2022.PublishedJuly2022.Originallyapproved
in 2011. Last previous edition approved in 2017 as D7771 – 17a. DOI: 10.1520/
D7771-17AR22. Available from United States Environmental Protection Agency (EPA), Ariel
For referenced ASTM standards, visit the ASTM website, www.astm.org, or Rios Bldg., 1200 Pennsylvania Ave., NW, Washington, DC 20004, http://
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM www.epa.gov/epaoswer/hazwaste/test/new-meth.htm#8270D.
Standards volume information, refer to the standard’s Document Summary page on Available from the U.S. Government Printing Office, Superintendent of
the ASTM website. Documents, 732 N. Capital St., NW., Washington, DC 20402-0001.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7771 − 17a (2022)
TABLE 1 Native and Deuterated BaP Compounds
C13 Labeled
Native PAH CAS# Deuterated PAH CAS# CAS#
PAH
Benzo-α-pyrene 50-32-8 d -Benzo-α-pyrene 63466-71-7 13C -Benzo-α- Not Available
12 4
pyrene
6.2 Extraction Thimbles, glass or cellulose, approximately 6.17 Drying Oven, gravity convection type, capable of
50- to 70-cm capacity. For instance, glass extraction thimble maintaining 40 6 10°C, used for slowing down the cooling
of 35-mm diameter by 90-mm height with course porosity (70 when the glassware is taken out of the muffle furnace.
to 100 µm similar to Ace Glass Size C, Porosity B, Code-14).
6.18 Furnace, capable of temperature regulation of 500 6
6.3 Heating Mantle,compatiblewithboilingflaskdescribed 25°C, used to burn off organic contamination from glass
in 6.4. surfaces.
6.4 Boiling Flasks for Soxhlet, for example, 250 cm . 6.19 Manometer, capable of pressure readings in the range
of 5 6 0.3 kPa.
6.5 Glass Beads, approximately 180 to 250 µm (60/80
mesh) if glass thimbles are used. Need to be very clean or
7. Reagents and Materials
toluene extracted.
7.1 Purity of Reagents—Reagent-grade chemicals shall be
6.6 PTFE or Glass Boiling Beads, approximately 3 mm.
used in all tests. Unless otherwise indicated, it is intended that
6.7 Glass Wool, need to be very clean or toluene extracted. all reagents conform to the specifications of the Committee on
Analytical Reagents of the American Chemical Society where
6.8 Rotary Evaporator, with temperature-controlled water
such specifications are available. Other grades may be used,
bath, automatic pressure regulation, and solvent-proof mem-
provided it is first ascertained that the reagent is of sufficiently
brane vacuum pump.
high purity to permit its use without lessening the accuracy of
6.9 Nitrogen Blow-Down Apparatus, equipped with a con-
the determination.
trolled water bath and nitrogen pressure control.
7.2 Separate stock solutions of the native BaPstandards and
6.10 Pear-Shaped Flasks for Rotary Evaporator, for
of the internal standard (deuterated or C13-labeled) can be
example, 25, 50, and 100 cm .
purchased as premade solutions or prepared from solid mate-
6.11 GC/MS, with autosampler. rials (Table 1).
6.11.1 MS with electron impact (EI) capability and single- 7.2.1 A concentration range of 80 to 100 µg/cm for the
ion monitoring (SIM) mode. native BaP analyte stock solution is recommended.
6.11.2 GC Capillary Column, usually a nonpolar GC col- 7.2.2 A similar concentration range of 80 to 100 µg/cm of
umn composed of 5 % phenyl-methyl silicone coating is used the deuterated (d -benzo-α-pyrene) or isotopically-labeled
for PAH analysis. (13C -benzo-α-pyrene) is recommended for the internal stan-
6.11.3 Deactivated Straight Borosilicate Liner with Small dard (IS) stock solution.
7.2.3 All purchased BaP standard materials shall be 98 %
Piece of Deactivated Glass Wool—This liner may be used as
long as peak resolution is satisfactory. pure or better and certified with respect to their purity and
concentration by the manufacturer. Follow the manufacturer’s
6.11.4 Alternative liner is a split/splitless nondeactivated
liner with glass wool (4-mm internal diameter, straight liner). recommendation on how best to store the standard solutions.
Typically, the compounds are protected from light. They
This shall be deactivated with a silanizing agent before use.
Another alternative is a split/splitless liner with fluorocarbon should be checked frequently for signs of degradation or
evaporation. The BaP standard stock solutions shall be
liner seals. Such a liner will already contain conditioned
silanized glass wool. Other liners can be used if they produce replaced/recertified on a yearly basis or sooner if comparisons
acceptable results. with quality control (QC) samples indicate a problem.
6.11.5 Gold-plated seal for GC injector port or similar
7.3 Toluene, suitable for high resolution gas chromatogra-
nonreactive seal.
phy analysis (99.99 % pure).
6.11.6 GC/MS amber autosampler vials with polytetrafluo-
7.4 Acetone, suitable for high resolution gas chromatogra-
roethylene (PTFE)-coated caps.
phy analysis (99.99 % pure).
6.11.7 Crimping tool.
7.5 Helium, GC/MS purity grade.
6.12 Adjustable Micropipettes, 1000, 200, and 20 µL.
7.6 Nitrogen, analytical purity grade.
6.13 Microliter Syringes of Different Volumes, for example,
10 and 100 µL.
Reagent Chemicals, American Chemical Society Specifications, American
6.14 Amber Glass Vials, approximately 4 cm with caps
Chemical Society, Washington, DC. For suggestions on the testing of reagents not
(rubber with PTFE back).
listed by the American Chemical Society, see Analar Standards for Laboratory
Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia
6.15 Amber Volumetric Flasks, 2, 3, 5, 10, 25, and 100 cm .
and National Formulary, U.S. Pharmacopeial convention, Inc. (USPC), Rockville,
6.16 Analytical Balance, with an accuracy of 0.01 mg. MD.
D7771 − 17a (2022)
7.7 Silica gel columns for Solid Phase Extraction (SPE) µg/cm ). A lower BaP concentration range can be used for the
removal of polar compounds. case of high-purity carbon blacks. However, the IS concentra-
7.7.1 Silica SPE Cartridges, single-use application, having tion should maintain an S/N ratio of at least 15/1 for routine
3 6
a volume capacity of approximately 1 to 10 cm . instrument performance. Subsections 9.2 – 9.4 describe the
7.7.1.1 Preparation of Silica SPE Cartridge—Follow the preparation of the various solutions required.
manufacturer’s instruction for preparation and use. The typical
9.2 Preparation of Native BaP Standard Solutions for
method of preparation is to wet the cartridge with approxi-
Calibration—Using the native BaP standard stock solution
mately 10 cm of the elution solvent (toluene). Discard the 3
described in 7.2, prepare at least 10 cm of five toluene
wetting solvent.
solutions in amber glassware at the concentrations suggested
7.7.2 Alternative SPE Method: Silica Gel/13 % H O Grav-
below. Other concentrations may be used but the difference
ity Column:
between any two concentration levels shall not exceed a factor
7.7.2.1 Preparation of a Silica Gel/13 % H O Adsorbent—
of four. Before diluting to the final solution volume, spike each
Pour 200 g silica gel (high purity grade, type 60, particle size
standard with the appropriate volume (for example, 100 µL IS
0.063 to 0.200 mm) into a screw cap glass bottle and add 30 g
solution described in 9.3) to give a final IS concentration of
ofdeionizedwaterinsmallportions(forexample,2cm )using 3
0.500µg/cm .Otheraliquotvolumesandfinalvolumesmaybe
a suitable pipette. After addition of each portion of water, the
used to obtain the desired concentrations. Cap the standard
silica gel bottle is shaken to evenly distribute the wetted silica
solutions securely, mix thoroughly, and label.
gel. No aggregation should occur during this process. If so,
Native BaP Standard 5 1.00 µg/cm
shaking must be continued until a homogeneous material is 3
Native BaP Standard 4 0.500 µg/cm
obtained. Finally, the closed bottle is shaken for 8 hours by
Native BaP Standard 3 0.200 µg/cm
Native BaP Standard 2 0.0500 µg/cm
means of an overhead shaker. If properly closed and stored, the
Native BaP Standard 1 0.0125 µg/cm
adsorbent should be viable for at least 6 months.
9.3 Preparation of Diluted IS Solution—Using the IS stock
7.7.2.2 Preparation of a Silica Gel/13 % H O Gravity
solution described in 7.2, prepare a convenient volume (for
Column—Insert a glass wool plug into the bottom of a pipette
example, 10 cm ) of diluted internal standard solution that will
tip (for example, 8 to 10 mm inner diameter and 5 cm
be later added to samples and calibration standards.Aconcen-
capacity). Place1gofthe silica gel/13 % H O in the column
tration of 50.0 µg/cm is suggested for this diluted IS solution
and tap the column gently to settle the silica gel. Cover the
in order to achieve a final concentration of 0.500 µg/cm in the
adsorbent layer with a glass wool plug and pre-elute the
extract sample.
column with 5 cm of cyclohexane. Discard the cyclohexane
eluate.
NOTE 1—Other concentrations within the calibration range can be used
as well.
8. Hazards
9.4 All standard solutions shall be stored in amber glass-
8.1 This test involves hazardous materials, operations, and
ware and kept in a refrigerator (<6°C) when not in use. Care
equipment. This procedure does not attempt to address the
has to be taken not to exceed their shelf life. If any indication
safety problems associated with this test. A hazards review
of degradation is perceived, then new standards have to be
shallbeconductedbyallpersonnelperformingthetest.Itisthe
prepared.
responsibility of the user to review all material safety data
sheets (MSDS), manuals, and hazards procedures and establish
10. Carbon Black Sample Preparation and Extraction
the appropriate safety measures. Some PAH compounds have
10.1 All glassware parts coming into contact with the
been shown to possess mutagenic as well as carcinogenic and
sample shall be BaP free on the basis of the limits of
teratogenicproperties.Assuch,concentratedextractsofcarbon
quantification. It is strongly recommended to use separate
blacks containing PAHs also may possess the same harmful
glassware and extraction units for high-purity carbon blacks
properties. Solvents used are flammable. Appropriate personal
and carbon blacks in which higher BaP levels are expected.
protection equipment (PPE) shall be used.
Blanks should be run on a regular basis.
9. Preparation of Standard Solutions
10.2 Glassware should be rinsed with toluene and acetone
after use. The glassware is then dried at 150°C in a laboratory
9.1 TheGC/MSinstrumentiscalibratedusingfivesolutions
drying oven.
of the native BaPand internal standard (IS).The recommended
BaP concentrations are to cover a range of 0.0125 to 1.0
10.3 For low BaP carbon blacks, a pre-extraction of the
µg/cm (ppm). Other concentrations may be used as needed for
extraction unit for at least4his recommended. If glass
the application. The IS concentration is kept constant within
thimbles are not baked in a furnace as described in 10.5, then
the calibration range. Preferably the IS concentration is in the
the thimbles should be included in the 4 h pre-extraction.
middleoftheselectedcalibrationrange(forexample,0.3to0.6
Cellulosethimblesshouldbeincludedinthe4hpre-extraction.
In this case, the thimbles are further dried, for example, in a
6 vacuum drying oven prior to use.
The sole source of supply of the Sep-Pak cartridges known to the committee at
this time is Waters, 34 Maple Street, Milford, MA01757 (www.waters.com). If you
10.4 Disposable devices such as cellulose thimbles are
are aware of alternative suppliers, please provide this information to ASTM
rinsed with toluene and dried prior to use, for example, in a
International Headquarters. Your comments will receive careful consideration at a
meeting of the responsible technical committee, which you may attend. vacuum oven.
D7771 − 17a (2022)
10.5 If repeated cleanings and extractions do not produce 10.11.2.1 An interruption in the water flow triggers the
clean blanks, certain parts of the glassware may also be baked timer to stop, the heating mantles to turn off, and the solenoid
for at least 6 h in a furnace at, for example, 500°C.This is also valve to turn off; and
valid for glass extraction thimbles if used. It shall be deter- 10.11.2.2 A power outage stops the timer, switches off the
mined with the manufacturer if the glass parts can sustain such solenoid valve, and prevents the heating mantles from turning
temperature—for example, it is unlikely the Soxhlet can back on once power is restored.
sustain this.
10.12 Nitrogen should continuously flow through a mani-
10.6 If glass extraction thimbles are used, they should be fold connected to the condensers throughout the entire extrac-
checked for their drain rate at room temperature by pouring 50 tion period at a very low flow rate of approximately 10 to 15
3 3
cm of toluene inside the thimble. The time for 40 cm to drip sccm (standard cubic centimeters per minute). If the flow rate
out of the thimble should not exceed 95 s. Otherwise, the is too high, toluene may evaporate from the Soxhlet.
thimble is to be discarded. Dry the thimbles with clean
10.13 Turn the heating mantles on low.
nitrogen.
10.14 After 5 to 20 min, the flasks should be on the verge of
10.7 If glass extraction thimbles are used, pour the 60/80-
boiling. Gently agitate the apparatus; this should initiate the
mesh glass beads into the thimbles to a depth of 1 cm. Sizes
toluene boiling. Once this occurs, turn the heat to a higher
other than 60/80 mesh may be used.
setting. After about 30 min, check the Soxhlet assembly to
10.8 Weigh 10 6 0.1 g to the nearest 1 mg of the beaded ensure that the toluene is dripping from the condenser.
carbon black sample into the dried extraction thimble. Record
10.15 After at least4hof extraction, check and adjust the
the exact value as W .
CB
heater such that:
10.8.1 Fluffy or powder carbon black should be densified
10.15.1 The cycle time of each Soxhlet is less than 6 min
with toluene before extraction.This is accomplished by weigh-
(approximately ten cycles per hour). This is the length of time
ing 10 6 0.1 g of carbon black into a beaker and adding
for the Soxhlet to fill and the solvent to siphon out through the
toluene in approximately 1-cm aliquots and mixing the
siphon arm. Note that this is not the drain time. Drain time is
toluene into the carbon black with a spatula after each aliquot
described in 10.15.2.
isadded.Thisdensifiesthecarbonblackandformspellets.Add
10.15.2 If glass extraction thimbles are used, the drain time
sufficient toluene to densify the entire sample into crude
of the thimbles should be less than 15 min. This is the time for
pellets. The beakers shall then be left in the hood overnight to
the solvent to drain out of the thimble. This is measured by
evaporate the solvent. Once the solvent has evaporated, break
lowering the heat (to stop the solvent dripping from the
up the larger of the carbon black pellets with a spatula. The
condenser) and visually measuring the length of time for most
entire amount of pelletized black is then transferred to the
of the solvent to drain through the thimble. If the drain time
thimble.
deviates from the above value, replace the thimble and restart
10.9 Place a plug of glass wool or fold the top of the the extraction.
cellulose thimble above the black. The plug of wool should be
10.16 Extract samples continuously for 16 h and the toluene
placed such that the glass wool is in contact with the carbon
level should be checked from time to time for potential losses
black. This facilitates drainage of solvent through the glass
throughevaporation.ToavoiddegradationoftheextractedBaP
wool and into the carbon black bed.
by overheating of glass walls, a sufficient level of toluene shall
10.10 Add a few glass boiling beads into the clean 250-cm always remain in the boiling flask especially at the point at
boiling flask and pour approximately 150 cm of toluene. which the Soxhlet is filled and the solvent is starting to siphon
Assemble the extraction apparatus. To maintain temperature out.
uniformity throughout the system, wrap the Soxhlet extractor
10.17 If the remaining solvent volume becomes too small,
and the boiling flask with aluminum foil. Record the Soxhlet
the extraction has to be interrupted and fresh toluene be added
position number, thimble identification (for glass thimbles),
to the extractor after cool down. The nitrogen flow should be
and extraction date.
checked and adjusted, if necessary. The extraction is subse-
10.11 Extraction Settings and Conditions: quently continued to complete the required extraction time.
10.11.1 Samples are extracted for 16 h.
11. Extract Preparation before the GC/MS Analysis
NOTE 2—Hamm et al demonstrated that 16 h were sufficient to collect
over 95 % of the BaP extractable in 48 h from a relatively high PAH
11.1 Two extract preparation procedures (PartAand Part B)
content carbon black.
are given below. Either procedure may be used.
10.11.2 Turn on the water flow. It is recommended that a
Part A
water-flow monitor, a solenoid valve to switch the water flow
on or off, and a timer be assembled such that:
11.2 Once the set extraction time has elapsed, the Soxhlet
assembly is cooled and the thimble is removed.
11.3 The raw toluene extract is transferred to a rotary
Hamm et al, “Investigations on the extraction and migration behavior of
evaporator and concentrated down to about 10 cm³. The rotary
polycyclic aromatic hydrocarbons (PAHs) from cured rubber formulations contain-
evaporatorshallbesettoamaximumbathtemperatureof40 6
ing carbon black as reinforcing agent,” Rubber Chemistry & Technology, Vol 82,
Issue 2, 2009. 2°C and a vacuum of 5 6 0.3 kPa. These parameters shall be
D7771 − 17a (2022)
monitored carefully during all evaporation steps as BaP losses brought to approximately 1 cm by addition of fresh toluene
may occur.Alternative evaporators or vacuum and temperature and mixed thoroughly.
settings or both may be used provided recovery studies are
11.6.3 Record the volume of the extract portion taken for
conducted and results of these studies are acceptable.
analysis (V ) and the volume of the internal standard solution
A
added to this extract aliquot.
11.4 Quantitatively transfer the extract into a 20 cm amber
volumetric flask. Rinse the boiling flask at least 3 times with
11.7 Purificationoftheextractportionmaybeperformedby
approximately 2 cm of fresh toluene and pass them also into
means of commercially available Silica Solid Phase Extraction
the volumetric flask. Bring the toluene extract to exactly 20
cartridges (SPE-cartridges, see 7.7.1). Follow the manufactur-
cm , cap securely, mix thoroughly, and label. If an aliquot of
er’s guidelines for removal of polar compounds from the
theconcentratedextractistaken,thentheinitialextractvolume
tolueneextract.Alternatively,self-preparedsilicacolumnsmay
(V)is20cm .
i
also be used as described in 7.7.2. In both cases the elution
NOTE3—Concentrationtestswith200cm toluenesolutionscontaining
behavior of the column with respect to BaPhas to be validated
50 ng of BaP indicated that no measurable losses occurred when
byrecoverystudiesforeachmethod.Subsection7.7.1provides
narrowing even to a volume of 5 cm (at 40°C water bath temperature and
5-kPa pressure).
an example of the extract purification by means of a silica
O gravity column. Preparation of the silica gel/13
gel/13 % H
11.5 Depending on the expected level of BaP in the carbon
%H O solid phase is described in 7.7.2.1, whereas preparation
black, the entire raw extract or a suitable aliquot is used for
of the column used for the example of 11.7.1 is specified in
analysis. For low levels of BaP, 100 % or 50 % of the extract
7.7.2.2.
may be appropriate. If higher BaPlevels are expected, aliquots
of 10 % or 1 % may be used for BaPdetermination.The use of 11.7.1 Forextractpurificationusingthesilicagel/13%H O
smaller aliquots for higher BaP level carbon blacks easily gravity column described in 7.7.2.2, quantitatively transfer the
allows adjustment of the BaP concentration in the final
concentratedorvolumeadjustedextract(approximately1cm )
measurement solution to the calibration range of the GC/MS,
onto the top of the pre-eluted and still cyclohexane-wetted
without further dilution steps.
silica gel/13 % H O column. Rinse the pear-shaped rotary
evaporator flask or the conical-bottom centrifuge glass 3 times
NOTE 4—The color of the extract obtained might give an indication of
with 0.5 cm of cyclohexane and add the rinse solutions to the
the expected BaPlevel.Though difficult to assess and essentially based on
experience, high-purity carbon blacks tend to exhibit colorless extracts or top of the SPE column. Subsequently, elute the PAH fraction
with a slight tinge of yellow, while higher BaP level carbon blacks
from the SPE column by means of 9 cm of cyclohexane.
produce yellow to orange extracts.Typically, 100 % or 50 % of the extract
C
...