ETHYLENE OXIDE: METHOD 1614, Issue 2, dated 15 August 1994 - Page 4 of 6
14.
15.
parabolic) least squares fit if necessary to obtain the best fit of the data. Determine recovery (R) at least once for each lot of charcoal used for sampling in the concentration range of interest. Prepare three tubes at each concentration of interest plus three media blanks. a. Remove and discard back sorbent section of a media blank sampler. b. Inject a known amount (2 to 15 µL) of EtO stock solution or a serial dilution thereof directly onto the charcoal with a microliter syringe. c. Cap the tube. Allow to stand overnight. d. Desorb (steps 5 through 8) and analyze together with working standards (steps 9 through 12 and 16 and 17). Analyze three quality control blind spikes and three analyst spikes to ensure that the calibration graph and DE graph are in control.
MEASUREMENT: 16. 17.
Set gas chromatograph according to manufacturer's recommendations and to conditions given on page 1614-1. Inject sample aliquot manually using solvent-flush technique or with autosampler. Measure peak area.
CALCULATIONS: 18.
19.
Determine the mass, µg (corrected for R), of EtO found in the sample front (W f) and back (Wb) sorbent sections, and in the average media blank front (B r) and back (Bb) sorbent sections. NOTE: If Wb > Wf/10, report breakthrough and possible sample loss. Calculate concentration, C, of EtO in the air volume sampled, V(L):
C
(W f
Wb
Bf V
Bb)
, mg/m 3.
EVALUATION OF METHOD: This method uses HBr-coated charcoal to collect EtO and rapidly convert it to 2-bromoethanol. This method was evaluated at the OSHA Analytical Laboratory, Salt Lake City, UT, as OSHA Method 50 [1]. Fifteen-min and 30-min air samples were collected from a constant 5-ppm test atmosphere (80% relative humidity, ambient temperature) at 0.1 L/min with observed recoveries in the range 88 to 100%. Fifteen pairs of side-by-side area samples were collected and analyzed by OSHA using this method and the Qazi-Ketcham method. The sampling rate was ca. 50 mL/min for 4 to 7.5 H. Results showed no statistical difference in the two methods, with no bias over the range 0.3 to 7 ppm EtO. test atmospheres of 0.1, 0.5, 1.0, and 16 ppm at 70 to 80% relative humidity and ambient temperature were sampled for 4 h at 0.1 L/min with no breakthrough. The 5% breakthrough volume for sampling a 16-ppm atmosphere of EtO at 0.15 L/min was 39 L. No significant storage effects were observed for samples in the 0.1 to 16 ppm range at high humidity and stored at ambient temperature for a minimum of two weeks. The precision, Sr, of chromatographic response of working standards in the range 18 to 71 µg EtO per sample was 0.028 [1]. Recovery of EtO spikes in NIOSH laboratories averaged 75% at 11, 22, 33, and 44 µg EtO per sample.
REFERENCES: [1] [2] [3]
Cummins, K.J. OSHA Method No. 50, "Ethylene Oxide," OSHA Analytical Laboratory, Salt Lake City, UT (unpublished, January, 1985). User check, DataChem, Inc., NIOSH Seq. #5860-J (unpublished, May 15, 1987). NOSH Manual of Analytical Methods, 2nd. ed., V. 3, S286, U.S. Department of Health, Education, and Welfare, Publ. (NIOSH) 77-157C (1977); also cited in NIOSH Special Occupational Hazard NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94
