California Code of Regulations › Title 8 - Industrial Relations › Division 1 - Department of Industrial Relations › Chapter 4 - Division of Industrial Safety › Subchapter 7 - General Industry Safety Orders › Group 16 - Control of Hazardous Substances › Article 110 - Regulated Carcinogens › Appendix D - Sampling and Analytical Methods for Acrylonitrile

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
There are many methods available for monitoring
						  employee exposures to acrylonitrile. Most of these involve the use of charcoal
						  tubes and sampling pumps, with analysis by gas chromatograph. The essential
						  differences between the charcoal tube methods include, among others, the use of
						  different desorbing solvents, the use of different lots of charcoal, and the
						  use of different equipment for analysis of the samples.
Besides charcoal, considerable work has been performed
						  on methods using porous polymer sampling tubes and passive dosimeters. In
						  addition, there are several portable gas analyzers and monitoring units
						  available on the open market.
This appendix contains details for the methods which
						  have been tested at OSHA Analytical Laboratory in Salt Lake City, and NIOSH in
						  Cincinnati. Each is a variation on NIOSH Method S
						  156, which is also included for
						  reference. This does not indicate that these methods are the only ones which
						  will be satisfactory. There also may be workplace situations in which these
						  methods are not adequate, due to such factors as high humidity.
Employers who note problems with sample breakthrough
						  should try larger charcoal tubes. Tubes of larger capacity are available, and
						  are often used for sampling vinyl chloride. In addition, lower flow rates and
						  shorter sampling times should be beneficial in minimizing breakthrough
						  problems.
Whatever method the employer chooses, he must assure
						  himself of the method's accuracy and precision under the unique conditions
						  present in his workplace.
NIOSH Method S
						  156 (Unmodified)
Analyte: Acrylonitrile
Matrix: Air
Procedure: Adsorption on charcoal, desorption with
						  methanol, GC.
1. Principle of the method (Reference 11.1).
1.1 A known volume of air is drawn through a charcoal
						  tube to trap the organic vapors present.
1.2 The charcoal in the tube is transferred to a small,
						  stoppered sample container, and the analyte is desorbed with methanol.
1.3 An aliquot of the desorbed sample is injected into
						  a gas chromatograph.
1.4 The area of the resulting peak is determined and
						  compared with areas obtained for standards.
2. Range and sensitivity.
2.1 This method was validated over the range of
						  17.5-70.0 mg/cu m at an atmospheric temperature and pressure of 22° C and
						  760 mm Hg, using a 20-liter sample. Under the conditions of sample size (20
						  liters) the probable useful range of this method is 4.5-135 mg/cu m. The method
						  is capable of measuring much smaller amounts if the desorption efficiency is
						  adequate. Desorption efficiency must be determined over the range used.
2.2 The upper limit of the range of the method is
						  dependent on the adsorptive capacity of the charcoal tube. This capacity varies
						  with the concentrations of acrylonitrile and other substances in the air. The
						  first section of the charcoal tube was found to hold at least 3.97 mg of
						  acrylonitrile when a test atmosphere containing 92.0 mg/cu m of acrylonitrile
						  in air was sampled 0.18 liter per minute for 240 minutes; at that time the
						  concentration of acrylonitrile in the effluent was less than 5 percent of that
						  in the influent. (The charcoal tube consists of two sections of activated
						  charcoal separated by a section of urethane foam. See section
						  6.2). If a particular atmosphere is
						  suspected of containing a large amount of contaminant, a smaller sampling
						  volume should be taken.
3. Interference.
3.1 When the amount of water in the air is so great
						  that condensation actually occurs in the tube, organic vapors will not be
						  trapped efficiently. Preliminary experiments using toluene indicate that high
						  humidity severely decreases the breakthrough volume.
3.2 When interfering compounds are known or suspected
						  to be present in the air, such information, including their suspected
						  identities, should be transmitted with the sample.
3.3 It must be emphasized that any compound which has
						  the same retention time as the analyte at the operating conditions described in
						  this method is an interference. Retention time data on a single column cannot
						  be considered proof of chemical identity.
3.4 If the possibility of interference exists,
						  separation conditions (column packing, temperature, etc.) must be changed to
						  circumvent the problem.
4. Precision and accuracy.
4.1 The Coefficient of Variation (CV1) for the total
						  analytical and sampling method in the range 17.5-70.0 mg/cu m was 0.073. This
						  value corresponds to a 3.3 mg/cu m standard deviation at the (previous) OSHA
						  standard level (20 ppm). Statistical information and details of the validation
						  and experimental test procedures can be found in Reference 11.2.
4.2 On the average the concentrations obtained at the
						  20 ppm level using the overall sampling and analytical method were 6.0 percent
						  lower than the "true" concentrations for a limited number of laboratory
						  experiments. Any difference between the "found" and "true" concentrations may
						  not represent a bias in the sampling and analytical method, but rather a random
						  variation from the experimentally determined "true" concentration. Therefore,
						  no recovery correction should be applied to the final result in section
						  10.5.
5. Advantages and disadvantages of the method.
5.1 The sampling device is small, portable, and
						  involves no liquids. Interferences are minimal, and most of those which do
						  occur can be eliminated by altering chromatographic conditions. The tubes are
						  analyzed by means of a quick, instrumental method.
The method can also be used for the simultaneous
						  analysis of two or more substances suspected to be present in the same sample
						  by simply changing gas chromatographic conditions.
5.2 One disadvantage of the method is that the amount
						  of sample which can be taken is limited by the number of milligrams that the
						  tube will hold before overloading. When the sample value obtained for the
						  backup section of the charcoal tube exceeds 25 percent of that found on the
						  front section, the possibility of sample loss exists.
5.3 Furthermore, the precision of the method is limited
						  by the reproducibility of the pressure drop across the tubes. This drop will
						  affect the flow rate and cause the volume to be imprecise, because the pump is
						  usually calibrated for one tube only.
6. Apparatus.
6.1 A calibrated personal sampling pump whose flow can
						  be determined within ±5 percent at the recommended flow rate. (Reference
						  11.3).
6.2 Charcoal tubes: Glass tubes with both ends flame
						  sealed, 7 cm long with a 6-mm O.D. and a 4-mm I.D., containing 2 sections of
						  20/40 mesh activated charcoal separated by a 2-mm portion of urethane foam. The
						  activated charcoals prepared from coconut shells and is fired at 600° C
						  prior to packing. The adsorbing section contains 100 mg of charcoal, the backup
						  section 50 mg. A 3-mm portion of urethane
						  foam is placed between the outlet end of the tube and the backup section. A
						  plug of silicated glass wool is placed in front of the adsorbing section. The
						  pressure drop across the tube must be less than 1 inch of mercury at a flow
						  rate of 1 liter per minute.
6.3 Gas chromatograph equipped with a flame ionization
						  detector.
6.4 Column (4-ft X ¼ -in stainless steel) packed
						  with 50/80 mesh Poropak, type Q.
6.5 An electronic integrator or some other suitable
						  method for measuring peak areas.
6.6 Two-milliliter sample containers with glass
						  stoppers or Teflon-lined caps. If an automatic sample injector is used, the
						  associated vials may be used.
6.7 Microliter syringes: 10-microliter, and other
						  convenient sizes for making standards.
6.8 Pipets: 1.0-ml delivery pipets.
6.9 Volumetric flask: 10-ml or convenient sizes for
						  making standard solutions.
7. Reagents.
7.1 Chromatographic quality methanol.
7.2 Acrylonitrile, reagent grade.
7.3 Hexane, reagent grade.
7.4 Purified nitrogen.
7.5 Prepurified hydrogen.
7.6 Filtered compressed air.
8. Procedure.
8.1 Cleaning of equipment. All glassware used for the
						  laboratory analysis should be detergent washed and thoroughly rinsed with tap
						  water and distilled water.
8.2 Calibration of personal pumps. Each personal pump
						  must be calibrated with a representative charcoal tube in the line. This will
						  minimize errors associated with uncertainties in the sample volume
						  collected.
8.3 Collection and shipping of samples.
8.3.1 Immediately before sampling, break the ends of
						  the tube to provide an opening at least one-half the internal diameter of the
						  tube (2 mm).
8.3.2 The smaller section of charcoal is used as a
						  backup and should be positioned nearest the sampling pump.
8.3.3 The charcoal tube should be placed in a vertical
						  direction during sampling to minimize channeling through the charcoal.
8.3.4 Air being sampled should not be passed through
						  any hose or tubing before entering the charcoal tube.
8.3.5 A maximum sample size of 20 liters is
						  recommended. Sample at a flow of 0.20 liter per minute or less. The flow rate
						  should be known with an accuracy of at least ±5 percent.
8.3.6 The temperature and pressure of the atmosphere
						  being sampled should be recorded. If pressure reading is not available, record
						  the elevation.
8.3.7 The charcoal tubes should be capped with the
						  supplied plastic caps immediately after sampling. Under no circumstances should
						  rubber caps be used.
8.3.8 With each batch of 10 samples submit one tube
						  from the same lot of tubes which was used for sample collection and which is
						  subjected to exactly the same handling as the samples except that no air is
						  drawn through it. Label this as a blank.
8.3.9 Capped tubes should be packed tightly and padded
						  before they are shipped to minimize tube breakage during shipping.
8.3.10 A sample of the bulk material should be
						  submitted to the laboratory in a glass container with a Teflon-lined cap. This
						  sample should not be transported in the same container as the charcoal
						  tubes.
8.4 Analysis of samples.
8.4.1 Preparation of samples. In preparation for
						  analysis, each charcoal tube is scored with a file in front of the first
						  section of charcoal and broken open. The glass wool is removed and discarded.
						  The charcoal in the first (larger) section is transferred to a 2-ml stoppered
						  sample container. The separating section of foam is removed and discarded; the
						  second section is transferred to another stoppered container. These two
						  sections are analyzed separately.
8.4.2 Desorption of samples. Prior to analysis, 1.0 ml
						  of methanol is pipetted into each sample container. Desorption should be done
						  for 30 minutes. Tests indicate that this is adequate if the sample is agitated
						  occasionally during this period. If an automatic sample injector is used, the
						  sample vials should be capped as soon as the solvent is added to minimize
						  volatilization.
8.4.3 GC conditions. The typical operating conditions
						  for the gas chromatograph are:
1. 50 ml/min (60 psig) nitrogen carrier gas
						  flow.
2. 65 ml/min (24 psig) hydrogen gas flow to
						  detector.
3. 500 ml/min (50 psig) air flow to detector.
4. 235°C injector temperature.
5. 255°C manifold temperature (detector).
6. 155°C column temperature.
8.4.4 Injection. The first step in the analysis is the
						  injection of the sample into the gas chromatograph. To eliminate difficulties
						  arising from blowback or distillation within the syringe needle, one should
						  employ the solvent flush injection technique. The 10-microliter syringe is
						  first flushed with solvent several times to wet the barrel and plunger. Three
						  microliters of solvent are drawn into the syringe to increase the accuracy and
						  reproducibility of the injected sample volume. The needle is removed from the
						  solvent, and the plunger is pulled back about 0.2 microliter to separate the
						  solvent flush from the sample with a pocket of air to be used as a marker. The
						  needle is then immersed in the sample, and a 5-microliter aliquot is withdrawn,
						  taking into consideration the volume of the needle, since the sample in the
						  needle will be completely injected. After the needle is removed from the sample
						  and prior to injection, the plunger is pulled back 1.2 microliters to minimize
						  evaporation of the sample from the tip of the needle. Observe that the sample
						  occupies 4.9-5.0 microliters in the barrel of the syringe. Duplicate injections
						  of each sample and standard should be made. No more than a 3 percent difference
						  in area is to be expected. An automatic sample injector can be used if it is
						  shown to give reproducibility at least as good as the solvent flush
						  method.
8.4.5 Measurement of area. The area of the sample peak
						  is measured by an electronic integrator or some other suitable form of area
						  measurement, and preliminary results are read from a standard curve prepared as
						  discussed below.
8.5 Determination of desorption efficiency.
8.5.1 Importance of determination. The desorption
						  efficiency of a particular compound can vary from one laboratory to another and
						  also from one batch of charcoal to another. Thus, it is necessary to determine
						  at least once the percentage of the specific compound that is removed in the
						  desorption process, provided the same batch of charcoal is used.
8.5.2 Procedure for determining desorption efficiency.
						  Activated charcoal equivalent to the amount in the first section of the
						  sampling tube (100 mg) is measured into a 2.5-in, 4-mm I.D., glass tube, flame
						  sealed at one end. This charcoal must be from the same batch as that used in
						  obtaining the samples and can be obtained from unused charcoal tubes. The open
						  end is capped with Parafilm. A known amount of hexane solution of acrylonitrile
						  containing 0.239 g/ml is injected directly into the activated charcoal with a
						  microliter syringe, and tube is capped with more Parafilm. When using an
						  automatic sample injector, the sample injector vials, capped with Teflon-faced
						  septa, may be used in place of the glass tubes.
The amount injected is equivalent to that present in a
						  20-liter air sample at the selected level.
Six tubes at each of three levels (0.5X, 1X, and 2X of
						  the standard) are prepared in this manner and allowed to stand for at least
						  overnight to assure complete adsorption of the analyte onto the charcoal. These
						  tubes are referred to as the sample. A parallel blank tube should be treated in
						  the same manner except that no sample is added to it. The sample and blank
						  tubes are desorbed and analyzed in exactly the same manner as the sampling tube
						  described in section
						  8.4.
Two or three standards are prepared by injecting the
						  same volume of compound into 1.0 ml of methanol with the same syringe used in
						  the preparation of the samples. These are analyzed with the samples.
The desorption efficiency (D.E.) equals the average
						  weight in mg recovered from the tube divided by the weight in mg added to the
						  tube, or
D.E. = Average weight recovered (mg)/weight added
						  (mg)
The desorption efficiency is dependent on the amount of
						  analyte collected on the charcoal. Plot the desorption efficiency versus weight
						  of analyte found. This curve is used in section
						  10.4 to correct for adsorption
						  losses.
9. Calibration and standards.
It is convenient to express concentration of standards
						  in terms of mg/1.0 ml methanol, because samples are desorbed in this amount of
						  methanol. The density of the analyte is used to convert mg into microliters for
						  easy measurement with a microliter syringe. A series of standards, varying in
						  concentration over the range of interest, is prepared and analyzed under the
						  same GC conditions and during the same time period as the unknown samples.
						  Curves are established by plotting concentration in mg/1.0 ml versus peak
						  area.
NOTE: Since no internal standard is used in the method,
						  standard solutions must be analyzed at the same time that the sample analysis
						  is done. This will minimize the effect of known day-to-day variations and
						  variations during the same day of the FID response.
10. Calculations.
10.1 Read the weight, in mg, corresponding to each peak
						  area from the standard curve. No volume corrections are needed, because the
						  standard curve is based on mg/1.0 ml methanol and the volume of sample injected
						  is identical to the volume of the standards injected.
10.2 Corrections for the blank must be made for each
						  sample.
mg = mg sample - mg blank
Where:
mg sample = mg found in front section of sample
						  tube.
mg sample = mg found in front section of blank
						  tube.
A similar procedure is followed for the backup
						  sections.
10.3 Add the weights found in the front and backup
						  sections to get the total weight in the sample.
10.4 Read the desorption efficiency from the curve (see
						  sec. 8.5.2) for the amount found in the
						  front section. Divide the total weight by this desorption efficiency to obtain
						  the corrected mg/sample.
Corrected mg/sample = Total weight/D.E.
10.5 The concentration of the analyte in the air
						  sampled can be expressed in mg/cu m.
mg/cu m = Corrected mg (section
						  10.4) x 1,000
(liter/cu m)/air volume sampled
						  (liter)
10.6 Another method of expressing concentration is
						  ppm.
ppm = mg/cu x 24.45/M.W. x 760/P x T +
						  273/298
Where
P= Pressure (mm Hg) of air sampled.
T = Temperature (C) of air sampled.
24.45 = Molar volume (liter/mole) at 25°C and
						  760 mm Hg.
M.W. = Molecular weight (g/mole) of
						  analyte.
760 = Standard pressure (mm Hg).
298 = Standard temperature (K).
11. References.
11.1 White, L. D.
et al
., "A
						  Convenient Optimized Method for the Analysis of Selected Solvent Vapors in the
						  Industrial Atmosphere,"
American Industrial Hygiene Association
						  J.,
31 :225 (1970).
11.2 Documentation of NIOSH Validation Tests, NIOSH
						  Contract No. CDC-99-74-45.
11.3 Final Report, NIOSH Contract HSM-99-71-31,
						  "Personal Sampler Pump for Charcoal Tubes," September 15, 1972.
NIOSH Modification of NIOSH Method
						  S-156
The NIOSH recommended method for low levels for
						  acrylonitrile is a modification of method S-156. It differs in the following
						  respects:
(1) Samples are desorbed using 1 ml of 1 percent
						  acetone in CS2 rather than methanol.
(2) The analytical column and conditions are:
Column: 20 percent SP-1000 on 80/100 Supelcoport 10
						  feet x 1/8 -inch S.S.
Conditions:
Injector temperature: 200°C.
Detector temperature: 100°C.
Column temperature: 85°C.
Helium flow: 25 ml/min.
Air flow: 450 ml/min.
Hydrogen flow: 55 ml/min.
(3) A 2 [MICRO]l injection of the desorbed analyte is
						  used.
(4) A sampling rate of 100 ml/min is
						  recommended.
OSHA Laboratory Modification of NIOSH Method
						  S-156
Analyte: Acrylonitrile.
Matrix: Air
Procedure: Adsorption on charcoal, desorption with
						  methanol, GC
1. Principle of the Method (Reference 1)
1.1 A known volume of air is drawn through a charcoal
						  tube to trap the organic vapors present.
1.2 The charcoal in the tube is transferred to a small,
						  stoppered sample vial, and the analyte is desorbed with methanol.
1.3 An aliquot of the desorbed sample is injected into
						  a gas chromatograph.
1.4 The area of the resulting peak is determined and
						  compared with areas obtained for standards.
2. Advantages and disadvantages of the method.
2.1 The sampling device is small, portable, and
						  involves no liquids. Interferences are minimal, and most of those which do
						  occur can be eliminated by altering chromatographic conditions. The tubes are
						  analyzed by means of a quick, instrumental method.
2.2 This method may not be adequate for the
						  simultaneous analysis of two or more substances.
2.3 The amount of sample which can be taken is limited
						  by the number of milligrams that the tube will hold before overloading. When
						  the sample value obtained for the backup section of the charcoal tube exceeds
						  25 percent of that found on the front section, the possibility of sample loss
						  exists.
2.4 The precision of the method is limited by the
						  reproducibility of the pressure drop across the tubes. This drop will affect
						  the flow rate and cause the volume to be imprecise, because the pump is usually
						  calibrated for one tube only.
3. Apparatus.
3.1 A calibrated personal sampling pump whose flow can
						  be determined within ±5 percent at the recommended flow rate.
3.2 Charcoal tubes: Glass tube with both ends flame
						  sealed, 7 cm long with a 6-mm O.D. and a 4-mm I.D. containing 2 sections of
						  20/40 mesh activated charcoal separated by a 2-mm portion of urethane foam. The
						  activated charcoal is prepared from coconut shells and is fired at 600° C
						  prior to packing. The adsorbing section contains 100 mg of charcoal, the
						  back-up section
						  50 mg. A 3-mm portion of urethane
						  foam is placed between the outlet end of the tube and the back-up section. A
						  plug of silicated glass wool is placed in front of the adsorbing section. The
						  pressure drop across the tube must be less than one inch of mercury at a flow
						  rate of 1 liter per minute.
3.3 Gas chromatograph equipped with a nitrogen
						  phosphorus detector.
3.4 Column (10-ft x 1/8 -in stainless steel) packed
						  with 100/120 Supelcoport coated with 10 percent SP 1000.
3.5 An electronic integrator or some other suitable
						  method for measuring peak areas.
3.6 Two-milliliter sample vials with Teflon-lined
						  caps.
3.7 Microliter syringes: 10-microliter, and other
						  convenient sizes for making standards.
3.8 Pipets: 1.0-ml delivery pipets.
3.9 Volumetric flasks: convenient sizes for making
						  standard solutions.
4. Reagents.
4.1 Chromatographic quality methanol.
4.2 Acrylonitrile, reagent grade.
4.3 Filtered compressed air.
4.4 Purified hydrogen.
4.5 Purified helium.
5. Procedure.
5.1 Cleaning of equipment. All glassware used for the
						  laboratory analysis should be properly cleaned and free of organics which could
						  interfere in the analysis.
5.2 Calibration of personal pumps. Each pump must be
						  calibrated with a representative charcoal tube in the line.
5.3 Collection and shipping of samples.
5.3.1 Immediately before sampling, break the ends of
						  the tube to provide an opening at least one-half the internal diameter of the
						  tube (2 mm).
5.3.2 The smaller section of the charcoal is used as
						  the backup and should be placed nearest the sampling pump.
5.3.3 The charcoal should be placed in a vertical
						  position during sampling to minimize channeling through the charcoal.
5.3.4 Air being sampled should not be passed through
						  any hose or tubing before entering the charcoal tube.
5.3.5 A sample size of 20 liters is recommended. Sample
						  at a flow rate of approximately 0.2 liters per minute. The flow rate should be
						  known with an accuracy of at least 1±5 percent.
5.3.6 The temperature and pressure of the atmosphere
						  being sampled should be recorded.
5.3.7 The charcoal tubes should be capped with the
						  supplied plastic caps immediately after sampling. Rubber caps should not be
						  used.
5.3.8 Submit at least one blank tube (a charcoal tube
						  subjected to the same handling procedures, without having any air drawn through
						  it) with each set of samples.
5.3.9 Take necessary shipping and packing precautions
						  to minimize breakage of samples.
5.4 Analysis of samples.
5.4.1 Preparation of samples. In preparation for
						  analysis, each charcoal tube is scored with a file in front of the first
						  section of charcoal and broken open. The glass wool is removed and discarded.
						  The charcoal in the first (larger) section is transferred to a 2-ml vial. The
						  separating section of foam is removed and discarded; the second section is
						  transferred to another capped vial. These two sections are analyzed
						  separately.
5.4.2 Desorption of samples. Prior to analysis, 1.0 ml
						  of methanol is pipetted into each sample container. Desorption should be done
						  for 30 minutes in an ultrasonic bath. The sample vials are recapped as soon as
						  the solvent is added.
5.4.3 GC conditions. The typical operating conditions
						  for the gas chromatograph are:
1. 30 ml/min (60 psig) helium carrier gas flow.
2. 3.0 ml/min (30 psig) hydrogen gas flow to
						  detector.
3. 50 ml/min (60 psig) air flow to detector.
4. 200°C injector temperature.
5. 200°C dejector temperature.
6. 100°C column temperature.
5.4.4 Injection. Solvent flush technique or
						  equivalent.
5.4.5 Measurement of area. The area of the sample peak
						  is measured by an electronic integrator or some other suitable form of area
						  measurement, and preliminary results are read from a standard curve prepared as
						  discussed below.
5.5 Determination of desorption efficiency.
5.5.1 Importance of determination. The desorption
						  efficiency of a particular compound can vary from one laboratory to another and
						  also from one batch of charcoal to another. Thus, it is necessary to determine,
						  at least once, the percentage of the specific compound that is removed in the
						  desorption process, provided the same batch of charcoal is used.
5.5.2 Procedure for determining desorption efficiency.
						  The reference portion of the charcoal tube is removed. To the remaining
						  portion, amounts representing 0.5X, 1X, and 2X (X represents TLV) based on a 20
						  1 air sample are injected onto several tubes at each level. Dilutions of
						  acrylonitrile with methanol are made to allow injection of measurable
						  quantities. These tubes are then allowed to equilibrate at least overnight.
						  Following equilibration they are analyzed following the same procedure as the
						  samples. A curve of the desorption efficiency (amt. recovered/amt added) is
						  plotted versus amount of analyte found. This curve is used to correct for
						  adsorption losses.
6. Calibration and standards. A series of standards,
						  varying in concentration over the range of interest, is prepared and analyzed
						  under the same GC conditions and during the same time period as the unknown
						  samples. Curves are prepared by plotting concentration versus peak area.
NOTE: Since no internal standard is used in the method,
						  standard solutions must be analyzed at the same time that the sample analysis
						  is done. This will minimize the effect of known day-to-day variations and
						  variations during the same day of the NPD response. Multiple injections are
						  necessary.
7. Calculations. Read the weight, corresponding to each
						  peak area from the standard curve, correct for the blank, correct for the
						  desorption efficiency, and make necessary air volume
						  corrections.
1.
						  Editorial correction moving NOTE and HISTORIES 1-6 to precede Appendix A of
						  section 5213 (Register 99, No. 28). For
						  prior history of Appendices, see section
						  5213.