Page:NIOSH Manual of Analytical Methods - 3702.pdf/4

 ETHYLENE OXIDE: METHOD 3702, Issue 2, dated 15 August 1994 - Page 4 of 4 these bags should be discarded. (3) Segregate bags used for sample collection from those used for calibration standards.

MEASUREMENT: 4.

5.

Fill a gas-tight syringe, purged several times with sample, from the sample bag. Then empty it to the desired volume, and inject that volume into the chromatograph with a quick firm motion. Record identity of syringe. Use replicate analyses to determine the repeatability of the analysis. NOTE 1: If no estimate of concentration is available, use an injection volume of 10 to 25 µL at a high attenuation to reduce the possibility of column and detector overload. Depending on the results of this injection, larger volumes and/or more sensitive attenuations may be selected. NOTE 2: The procedure for analysis of samples collected directly in a gas tight syringe is the same as for bag samples, with the obvious elimination of the step where the sample is withdrawn from the bag. Along with the sample identification, record the injection volume (mL), the instrument attenuation, and the resultant peak height or area.

CALCULATIONS: 6.

Divide the EtO volume (nL) from the calibration graph, by the injection volume (mL) to calculate sample EtO concentration (ppm):

EVALUATION OF METHOD: This method was evaluated in the laboratory where the accuracy and precision were determined by a comparison of measured values with accepted concentrations from a dynamic (permeation tube) generation system with confirmation by lab G.C. with flame ionization detector [1]. Field evaluations were conducted in hospital and manufacturing sterilization facilities which used commercial mixtures of EtO with Freon 12 and carbon dioxide, respectively.

REFERENCES: [1] Burroughs G. E., and Busch, K. A., "Field Validation of Direct-Reading Instrumental Methods for the Sampling and Analysis of Environmental Contaminants," unpublished NIOSH report (1985). [2] NIOSH Manual of Analytical Methods, 3rd ed., Vol. 1, Method 1614, Department of Health and Human Services (NIOSH) Publ. No. 84-100 (1984).

METHOD WRITTEN BY: G. E. Burroughs, NIOSH/DPSE.

NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94