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 to Section 5200 - Sampling and Analytical Methods for MDA Monitoring and Measurement Procedures

Current through Register 2024 Notice Reg. No. 28, July 12, 2024
Measurements taken for the purpose of determining
						  employee exposure to MDA are best taken so that the representative average
						  8-hour exposure may be determined from a single 8-hour sample or two (2) 4-hour
						  samples. Short-time interval samples (or grab samples) may also be used to
						  determine average exposure level if a minimum of five measurements are taken in
						  a random manner over the 8-hour work shift. Random sampling means that any
						  portion of the work shift has the same chance of being sampled as any other.
						  The arithmetic average of all such random samples taken on one work shift is an
						  estimate of an employee's average level of exposure for that work shift. Air
						  samples should be taken in the employee's breathing zone (air that would most
						  nearly represent that inhaled by the employee).
There are a number of methods available for monitoring
						  employee exposures to MDA. The method OSHA currently uses is included
						  below.
The employer, however, has the obligation of selecting
						  any monitoring method which meets the accuracy and precision requirements of
						  the standard under his unique field conditions. The standard requires that the
						  method of monitoring must have an accuracy, to a 95 percent confidence level,
						  of not less than plus or minus 25 percent for the select PEL.
OSHA METHODOLOGY
Sampling Procedure. Apparatus:
Samples are collected by use of a personal sampling
						  pump that can be calibrated within +5% of the recommended flow rate with the
						  sampling filter in line.
Samples are collected on 37 mm Gelman type A/E glass
						  fiber filters treated with sulfuric acid. The filters are prepared by soaking
						  each filter with 0.5 mL of 0.26N
						  H2S04. (0.26 N
						  H2S04 can be prepared by diluting
						  1.5 mL of 36N H2504 to 200 mL
						  with deionized water.) The filters are dried in an oven at 100 degrees C for
						  one hour and then assembled into two-piece 37 mm polystyrene cassettes with
						  backup pads. The cassettes are sealed with shrink bands and the ends are
						  plugged with plastic plugs.
After sampling, the filters are carefully removed from
						  the cassettes and individually transferred to small vials containing
						  approximately 2 mL deionized water. The vials must be tightly sealed. The water
						  can be added before or after the filters are transferred. The vials must be
						  sealable and capable of holding at least 7 mL of liquid. Small glass
						  scintillation vials with caps containing Teflon liners are recommended.
Reagents. Deionized water is needed for addition to the
						  vials.
Sampling technique. Immediately before sampling, remove
						  the plastic plugs from the filter cassettes. Attach the cassette to the
						  sampling pump with flexible tubing and place the cassette in the employee's
						  breathing zone. After sampling, seal the cassettes with plastic plugs until the
						  filters are transferred to the vials containing deionized water. At some
						  convenient time within 10 hours of sampling, transfer the sample filters to
						  vials. Seal the small vials lengthwise. Submit at least one blank filter with
						  each sample set. Blanks should be handled in the same manner as samples, but no
						  air is drawn through them. Record sample volumes (in L of air) for each sample,
						  along with any potential interferences.
Retention efficiency. A retention efficiency study was
						  performed by drawing 100 L of air (80% relative humidity) at 1 L/min through
						  sample filters that had been spiked with 0.814 µg MDA. Instead of using
						  backup pads, blank acid-treated filters were used as backups in each cassette.
						  Upon analysis, the top filters were found to have an average of 91.8% of the
						  spiked amount. There was no MDA found on the bottom filters, so the amount lost
						  was probably due to the slight instability of the MDA salt.
Extraction efficiency. The average extraction
						  efficiency for six filters spiked at the target concentration is 99.6%. The
						  stability of extracted and derivatized samples was verified by reanalyzing the
						  above six samples the next day using fresh standards. The average extraction
						  efficiency for the reanalyzed samples is 98.7%.
Recommended air volume and sampling rate. The
						  recommended air volume is 100 L. The recommended sampling rate is 1
						  L/min.
Interferences (sampling). MDI appears to be a positive
						  interference. It was found that when MDI was spiked onto an acid-treated
						  filter, the MDI converted to MDA after air was drawn through it. Suspected
						  interferences should be reported to the laboratory with submitted
						  samples.
Safety precautions (sampling). Attach the sampling
						  equipment to the employees so that it will not interfere with work performance
						  or safety. Follow all safety procedures that apply to the work area being
						  sampled.
Analytical Procedure. Apparatus: The following are
						  required for analysis:
A GC equipped with an electron capture detector. For
						  this evaluation a Tracor 222 Gas Chromatograph equipped with a Nickel 63 High
						  Temperature Electron Capture Detector and a Linearizer was used.
A GC column capable of separating the MDA derivative
						  from the solyent and interferences. A 6 ft x 2 mm ID glass column packed with
						  3% OV-101 coated on 100/120 Gas Chrom Q was used in this evaluation.
An electronic integrator or some other suitable means
						  of measuring peak areas or heights.
Small resealable vials with Teflon-lined caps capable
						  of holding 4 mL.
A dispenser or pipet for toluene capable of delivering
						  2.0 mL.
Pipets (or repipets with plastic or Teflon tips)
						  capable of delivering 1 mL for the sodium hydroxide and buffer
						  solutions.
A repipet capable of delivering 25 µL
						  HFAA.
Syringes for preparation of standards and injection of
						  standards and samples into a GC.
Volumetric flasks and pipets to dilute the pure MDA in
						  preparation of standards.
Disposable pipets to transfer the toluene layers after
						  the samples are extracted.
Reagents.
0.5 NaOH prepared from reagent grade NaOH.
Toluene, pesticide grade. Burdick and Jackson distilled
						  in glass toluene was used.
Heptafluorobutyric acid anhydride (HFAA). HFAA from
						  Pierce Chemical Company was used.
pH 7.0 phosphate buffer, prepared from 136 g potassium
						  dihydrogen phosphate and 1 L deionized water. The pH is adjusted to 7.0 with
						  saturated sodium hydroxide solution.
4,4'-Methylenedianiline (MDA), reagent grade.
Standard Preparation. Concentrated stock standards are
						  prepared by diluting pure MDA with toluene. Analytical standards are prepared
						  by injecting µL amounts of diluted stock standards into vials that
						  contain 2.0 mL toluene. 25 µL HFAA are added to each vial and the vials
						  are capped and shaken for 10 seconds. After 10 min, 1 mL of buffer is added to
						  each vial. The vials are recapped and shaken for 10 seconds. After allowing the
						  layers to separate, aliquots of the toluene (upper) layers are removed with a
						  syringe and analyzed by GC. Analytical standard concentrations should bracket
						  sample concentrations. Thus, if samples fall out of the range of prepared
						  standards, additional standards must be prepared to ascertain detector
						  response.
Sample preparation. The sample filters are received in
						  vials containing deionized water. 1 mL of 0.5N NaOH and 2.0 mL toluene are
						  added to each vial. The vials are recapped and shaken for 10 min. After
						  allowing the layers to separate, approximately 1 mL aliquots of the toluene
						  (upper) layers are transferred to separate vials with clean disposable pipets.
						  The toluene layers are treated and analyzed.
Analysis. GC conditions:
Zone temperatures:
Column - 220
								  degrees C
Injector - 235 degrees C
Detector - 335 degrees C
Gas flows,
								  Ar/CH4:
Column - 28 mL/min
(95/5)
Purge - 40 mL/min
Iniection volume:
5.0
								  µL
Column:
6 ft x 1/8 in ID glass,
								  3% OV-101 on 100/120 Gas Chrom Q
Retention time of MDA
derivative:
3.5 min
Chromatogram:
Peak areas or
								  heights are measured by an integrator or other suitable means. A calibration
								  curve is constructed by plotting response (peak areas or heights) of standard
								  injections versus µg of MDA per sample. Sample concentrations must be
								  bracketed by standards.
Interferences (analytical). Any compound that gives an
						  electron capture detector response and has the same general retention time as
						  the HFAA derivative of MDA is a potential interference. Suspected interferences
						  reported to the laboratory with submitted samples by the industrial hygienist
						  must be considered before samples are derivatized. GC parameters may be changed
						  to possibly circumvent interferences. Retention time on a single column is not
						  considered proof of chemical identity. Analyte identity should be confirmed by
						  GC/MS if possible.
Calculations. The analyte concentration for samples is
						  obtained from the calibration curve in terms of µg MDA per sample. The
						  extraction efficiency is 100%. If any MDA is found on the blank, that amount is
						  subtracted from the sample amounts. The air concentrations are calculated using
						  the following formulae:
µg/m3 = (µg MDA
						  per sample)(1000)/(L of air sampled)
ppb =
						  (µg/m3)(24.46)/(198.3) =
						  (µg/m3)(0.1233) where 24.46 is the molar
						  volume at 25 degrees C and 760 mm Hg
Safety Precautions (analytical). Avoid skin contact and
						  inhalation of all chemicals. Restrict the use of all chemicals to a fume hood
						  if possible. Wear safety glasses and a lab coat at all times while in the lab
						  area.