OSHA Method No.: 56.
Target concentration: 1 ppm (2.21 mg/m(3))
Procedure: Air samples are collected by drawing known volumes of
air through sampling tubes containing charcoal adsorbent which has
been coated with 4-tert-butylcatechol. The samples are desorbed with
carbon disulfide and then analyzed by gas chromatography using a
flame ionization detector.
Recommended sampling rate and air volume: 0.05 L/min and 3 L.
Detection limit of the overall procedure: 90 ppb (200 ug/m(3))
(based on 3 L air volume).
Reliable quantitation limit: 155 ppb (343 ug/m(3)) (based on 3 L
Standard error of estimate at the target concentration: 6.5%.
Special requirements: The sampling tubes must be coated with
4-tert-butylcatechol. Collected samples should be stored in a
Status of method: A sampling and analytical method has been
subjected to the established evaluation procedures of the Organic
Methods Evaluation Branch, OSHA Analytical Laboratory, Salt Lake
City, Utah 84165.
This work was undertaken to develop a sampling and analytical
procedure for BD at 1 ppm. The current method recommended by OSHA for
collecting BD uses activated coconut shell charcoal as the sampling
medium (Ref. 5.2). This method was found to be inadequate for use at
low BD levels because of sample instability.
The stability of samples has been significantly improved through
the use of a specially cleaned charcoal which is coated with
4-tert-butylcatechol (TBC). TBC is a polymerization inhibitor for BD
1.1.1 Toxic effects
Symptoms of human exposure to BD include irritation of the eyes,
nose and throat. It can also cause coughing, drowsiness and fatigue.
Dermatitis and frostbite can result from skin exposure to liquid BD.
NIOSH recommends that BD be handled in the workplace as a potential
occupational carcinogen. This recommendation is based on two
inhalation studies that resulted in cancers at multiple sites in rats
and in mice. BD has also demonstrated mutagenic activity in the
presence of a liver microsomal activating system. It has also been
reported to have adverse reproductive effects. (Ref. 5.1)
1.1.2. Potential workplace exposure
About 90% of the annual production of BD is used to manufacture
styrene-butadiene rubber and Polybutadiene rubber. Other uses
include: Polychloroprene rubber, acrylonitrile butadiene-stryene
resins, nylon intermediates, styrene-butadiene latexes, butadiene
polymers, thermoplastic elastomers, nitrile resins, methyl
methacrylate-butadiene styrene resins and chemical intermediates.
1.1.3. Physical properties (Ref. 5.1)
CAS No.: 106-99-0
Molecular weight: 54.1
Appearance: Colorless gas
Boiling point: -4.41 deg. C (760 mm Hg)
Freezing point: -108.9 deg. C
Vapor pressure: 2 atm @ 15.3 deg. C; 5 atm @ 47 deg. C
Explosive limits: 2 to 11.5% (by volume in air)
Odor threshold: 0.45 ppm
Structural formula: H(2)C:CHCH:CH(2)
Synonyms: BD; biethylene; bivinyl; butadiene; divinyl;
buta-1,3-diene; alpha-gamma-butadiene; erythrene; NCI-C50602;
1.2. Limit defining parameters
The analyte air concentrations listed throughout this method are
based on an air volume of 3 L and a desorption volume of 1 mL. Air
concentrations listed in ppm are referenced to 25 deg. C and 760 mm
1.2.1. Detection limit of the analytical procedure
The detection limit of the analytical procedure was 304 pg per
injection. This was the amount of BD which gave a response relative
to the interferences present in a standard.
1.2.2. Detection limit of the overall procedure
The detection limit of the overall procedure was 0.60 ug per sample
(90 ppb or 200 ug/m(3)). This amount was determined graphically. It
was the amount of analyte which, when spiked on the sampling device,
would allow recovery approximately equal to the detection limit of
the analytical procedure.
1.2.3. Reliable quantitation limit
The reliable quantitation limit was 1.03 ug per sample (155 ppb or
343 ug/m(3)). This was the smallest amount of analyte which could be
quantitated within the limits of a recovery of at least 75% and a
precision (+/- 1.96 SD) of +/- 25% or better.
Footnote(1) The reliable quantitation limit and detection limits
reported in the method are based upon optimization of the instrument
for the smallest possible amount of analyte. When the target
concentration of an analyte is exceptionally higher than these
limits, they may not be attainable at the routine operation
The sensitivity of the analytical procedure over a concentration
range representing 0.6 to 2 times the target concentration, based on
the recommended air volume, was 387 area units per ug/mL. This value
was determined from the slope of the calibration curve. The
sensitivity may vary with the particular instrument used in the
The recovery of BD from samples used in storage tests remained
above 77% when the samples were stored at ambient temperature and
above 94% when the samples were stored at refrigerated temperature.
These values were determined from regression lines which were
calculated from the storage data. The recovery of the analyte from
the collection device must be at least 75% following storage.
1.2.6. Precision (analytical method only)
The pooled coefficient of variation obtained from replicate
determinations of analytical standards over the range of 0.6 to 2
times the target concentration was 0.011.
1.2.7. Precision (overall procedure)
The precision at the 95% confidence level for the refrigerated
temperature storage test was +/- 12.7%. This value includes an
additional +/- 5% for sampling error. The overall procedure must
provide results at the target concentrations that are +/- 25% at the
95% confidence level.
Samples collected from a controlled test atmosphere and a draft
copy of this procedure were given to a chemist unassociated with this
evaluation. The average recovery was 97.2% and the standard deviation
2. Sampling procedure
2.1.1. Samples are collected by use of a personal sampling pump
that can be calibrated to within +/- 5% of the recommended 0.05 L/min
sampling rate with the sampling tube in line.
2.1.2. Samples are collected with laboratory prepared sampling
tubes. The sampling tube is constructed of silane-treated glass and
is about 5-cm long. The ID is 4 mm and the OD is 6 mm. One end of the
tube is tapered so that a glass wool end plug will hold the contents
of the tube in place during sampling. The opening in the tapered end
of the sampling tube is at least one-half the ID of the tube (2 mm).
The other end of the sampling tube is open to its full 4-mm ID to
facilitate packing of the tube. Both ends of the tube are
fire-polished for safety. The tube is packed with 2 sections of
pretreated charcoal which has been coated with TBC. The tube is
packed with a 50-mg backup section, located nearest the tapered end,
and with a 100-mg sampling section of charcoal. The two sections of
coated adsorbent are separated and retained with small plugs of
silanized glass wool. Following packing, the sampling tubes are
sealed with two 7/32 inch OD plastic end caps. Instructions for the
pretreatment and coating of the charcoal are presented in Section 4.1
of this method.
2.3.1. Properly label the sampling tube before sampling and then
remove the plastic end caps.
2.3.2. Attach the sampling tube to the pump using a section of
flexible plastic tubing such that the larger front section of the
sampling tube is exposed directly to the atmosphere. Do not place any
tubing ahead of the sampling tube. The sampling tube should be
attached in the worker's breathing zone in a vertical manner such
that it does not impede work performance.
2.3.3. After sampling for the appropriate time, remove the
sampling tube from the pump and then seal the tube with plastic end
caps. Wrap the tube lengthwise.
2.3.4. Include at least one blank for each sampling set. The blank
should be handled in the same manner as the samples with the
exception that air is not drawn through it.
2.3.5. List any potential interferences on the sample data sheet.
2.3.6. The samples require no special shipping precautions under
normal conditions. The samples should be refrigerated if they are to
be exposed to higher than normal ambient temperatures. If the samples
are to be stored before they are shipped to the laboratory, they
should be kept in a freezer. The samples should be placed in a
freezer upon receipt at the laboratory.
(Breakthrough was defined as the relative amount of analyte found
on the backup section of the tube in relation to the total amount of
analyte collected on the sampling tube. Five-percent breakthrough
occurred after sampling a test atmosphere containing 2.0 ppm BD for
90 min at 0.05 L/min. At the end of this time 4.5 L of air had been
sampled and 20.1 ug of the analyte was collected. The relative
humidity of the sampled air was 80% at 23 deg. C.)
Breakthrough studies have shown that the recommended sampling
procedure can be used at air concentrations higher than the target
concentration. The sampling time, however, should be reduced to 45
min if both the expected BD level and the relative humidity of the
sampled air are high.
2.5. Desorption efficiency
The average desorption efficiency for BD from TBC coated charcoal
over the range from 0.6 to 2 times the target concentration was
96.4%. The efficiency was essentially constant over the range
2.6. Recommended air volume and sampling rate
2.6.1. The recommended air volume is 3L.
2.6.2. The recommended sampling rate is 0.05 L/min for 1 hour.
There are no known interferences to the sampling method.
2.8. Safety precautions
2.8.1. Attach the sampling equipment to the worker in such a
manner that it will not interfere with work performance or safety.
2.8.2. Follow all safety practices that apply to the work area
3. Analytical procedure
3.1.1. A gas chromatograph (GC), equipped with a flame ionization
Footnote(2) A Hewlett-Packard Model 5840A GC was used for this
evaluation. Injections were performed using a Hewlett-Packard Model
7671A automatic sampler.
3.1.2. A GC column capable of resolving the analytes from any
Footnote(3) A 20-ft x 1/8-inch OD stainless steel GC column
containing 20% FFAP on 80/100 mesh Chromabsorb W-AW-DMCS was used for
3.1.3. Vials, glass 2-mL with Teflon-lined caps.
3.1.4. Disposable Pasteur-type pipets, volumetric flasks, pipets
and syringes for preparing samples and standards, making dilutions
and performing injections.
3.2.1. Carbon disulfide.(4)
Footnote(4) Fisher Scientific Company A.C.S. Reagent Grade solvent
was used in this evaluation.
The benzene contaminant that was present in the carbon disulfide
was used as an internal standard (ISTD) in this evaluation.
3.2.2. Nitrogen, hydrogen and air, GC grade.
3.2.3. BD of known high purity.(5)
Footnote(5) Matheson Gas Products, CP Grade 1,3-butadiene was used
in this study.
3.3. Standard preparation
3.3.1. Prepare standards by diluting known volumes of BD gas with
carbon disulfide. This can be accomplished by injecting the
appropriate volume of BD into the headspace above the 1-mL of carbon
disulfide contained in sealed 2-mL vial. Shake the vial after the
needle is removed from the septum.(6)
Footnote(6) A standard containing 7.71 ug/mL (at ambient
temperature and pressure) was prepared by diluting 4 uL of the gas
with 1-mL of carbon disulfide.
3.3.2. The mass of BD gas used to prepare standards can be
determined by use of the following equations:
MV = ambient molar volume
BP = ambient barometric pressure
T = ambient temperature
ug/uL = 54.09/MV
ug/standard = (ug/uL)(uL) BD used to prepare the standard
3.4. Sample preparation
3.4.1. Transfer the 100-mg section of the sampling tube to a 2-mL
vial. Place the 50-mg section in a separate vial. If the glass wool
plugs contain a significant amount of charcoal, place them with the
appropriate sampling tube section.
3.4.2. Add 1-mL of carbon disulfide to each vial.
3.4.3. Seal the vials with Teflon-lined caps and then allow them
to desorb for one hour. Shake the vials by hand vigorously several
times during the desorption period.
3.4.4. If it is not possible to analyze the samples within 4
hours, separate the carbon disulfide from the charcoal, using a
disposable Pasteur-type pipet, following the one hour. This
separation will improve the stability of desorbed samples.
3.4.5. Save the used sampling tubes to be cleaned and repacked
with fresh adsorbent.
3.5.1. GC Conditions
Column temperature: 95 deg. C
Injector temperature: 180 deg. C
Detector temperature: 275 deg. C
Carrier gas flow rate: 30 mL/min
Injection volume: 0.80 uL
GC column: 20-ft x 1/8-in OD stainless steel GC column
FFAP on 80/100 Chromabsorb W-AW-DMCS.
3.5.2. Chromatogram. See Section 4.2.
3.5.3. Use a suitable method, such as electronic or peak heights,
to measure detector response.
3.5.4. Prepare a calibration curve using several standard
solutions of different concentrations. Prepare the calibration curve
daily. Program the integrator to report the results in ug/mL.
3.5.5. Bracket sample concentrations with standards.
3.6. Interferences (analytical)
3.6.1. Any compound with the same general retention time as the
analyte and which also gives a detector response is a potential
interference. Possible interferences should be reported by the
industrial hygienist to the laboratory with submitted samples.
3.6.2. GC parameters (temperature, column, etc.) may be changed to
3.6.3. A useful means of structure designation is GC/MS. It is
recommended that this procedure be used to confirm samples whenever
3.7.1. Results are obtained by use of calibration curves.
Calibration curves are prepared by plotting detector response against
concentration for each standard. The best line through the data
points is determined by curve fitting.
3.7.2. The concentration, in ug/mL, for a particular sample is
determined by comparing its detector response to the calibration
curve. If any analyte is found on the backup section, this amount is
added to the amount found on the front section. Blank corrections
should be performed before adding the results together.
3.7.3. The BD air concentration can be expressed using the
A = ug/mL from Section 3.7.2
B = volume
C = L of air sampled
D = efficiency
3.7.4. The following equation can be used to convert results in
mg/m(3) to ppm:
mg/m(3) = result from Section 3.7.3.
24.46 = molar volume of an ideal gas at 760 mm Hg and 25 deg. C.
3.8. Safety precautions (analytical)
3.8.1. Avoid skin contact and inhalation of all chemicals.
3.8.2. Restrict the use of all chemicals to a fume hood whenever
3.8.3. Wear safety glasses and a lab coat in all laboratory areas.
4. Additional Information
4.1. A procedure to prepare specially cleaned charcoal coated with
18.104.22.168. Magnetic stirrer and stir bar.
22.214.171.124. Tube furnace capable of maintaining a temperature of 700
deg. C and equipped with a quartz tube that can hold 30 g of
Footnote(8) A Lindberg Type 55035 Tube furnace was used in this
126.96.36.199. A means to purge nitrogen gas through the charcoal inside
the quartz tube.
188.8.131.52. Water bath capable of maintaining a temperature of 60
184.108.40.206. Miscellaneous laboratory equipment: One-liter vacuum
flask, 1-L Erlenmeyer flask, 350-M1 Buchner funnel with a coarse
fitted disc, 4-oz brown bottle, rubber stopper, Teflon tape etc.
220.127.116.11. Phosphoric acid, 10% by weight, in water.(9)
Footnote(9) Baker Analyzed" Reagent grade was diluted with water
for use in this evaluation.
18.104.22.168. 4-tert-Butylcatechol (TBC).(10)
Footnote(10) The Aldrich Chemical Company 99% grade was used in
22.214.171.124. Specially cleaned coconut shell charcoal, 20/40 mesh.(11)
Footnote(11) Specially cleaned charcoal was obtained from Supelco,
Inc. for use in this evaluation. The cleaning process used by Supelco
126.96.36.199. Nitrogen gas, GC grade.
Weigh 30g of charcoal into a 500-mL Erlenmeyer flask. Add about 250
mL of 10% phosphoric acid to the flask and then swirl the mixture.
Stir the mixture for 1 hour using a magnetic stirrer. Filter the
mixture using a fitted Buchner funnel. Wash the charcoal several
times with 250-mL portions of deionized water to remove all traces of
the acid. Transfer the washed charcoal to the tube furnace quartz
tube. Place the quartz tube in the furnace and then connect the
nitrogen gas purge to the tube. Fire the charcoal to 700 deg. C.
Maintain that temperature for at least 1 hour. After the charcoal has
cooled to room temperature, transfer it to a tared beaker. Determine
the weight of the charcoal and then add an amount of TBC which is 10%
of the charcoal, by weight.
CAUTION-TBC is toxic and should only be handled in a fume hood
while wearing gloves.
Carefully mix the contents of the beaker and then transfer the
mixture to a 4-oz bottle. Stopper the bottle with a clean rubber
stopper which has been wrapped with Teflon tape. Clamp the bottle in
a water bath so that the water level is above the charcoal level.
Gently heat the bath to 60 deg. C and then maintain that temperature
for 1 hour. Cool the charcoal to room temperature and then transfer
the coated charcoal to a suitable container.
The coated charcoal is now ready to be packed into sampling tubes.
The sampling tubes should be stored in a sealed container to prevent
contamination. Sampling tubes should be stored in the dark at room
temperature. The sampling tubes should be segregated by coated
adsorbent lot number.
The chromatograms were obtained using the recommended analytical
method. The chart speed was set at 1 cm/min for the first three min
and then at 0.2 cm/min for the time remaining in the analysis.
The peak which elutes just before BD is a reaction product between
an impurity on the charcoal and TBC. This peak is always present, but
it is easily resolved from the analyte. The peak which elutes
immediately before benzene is an oxidation product of TBC.
5.1. "Current Intelligence Bulletin 41, 1,3-Butadiene", U.S. Dept.
of Health and Human Services, Public Health Service, Center for
Disease Control, NIOSH.
5.2. "NIOSH Manual of Analytical Methods", 2nd ed; U.S. Dept. of
Health Education and Welfare, National Institute for Occupational
Safety and Health: Cincinnati, OH. 1977, Vol. 2, Method No. S91 DHEW
(NIOSH) Publ. (US), No. 77-157-B.
5.3. Hawley, G.C., Ed. "The Condensed Chemical Dictionary", 8th
ed.; Van Nostrand Rienhold Company: New York, 1971; 139.5.4. Chem.
Eng. News (June 10, 1985), (63), 22-66.
[61 FR 56746, Nov. 4, 1996]