Validation of an Evacuated Canister Method for Measuring Part-Per-Billion Levels of Chemical Warfare Agent Simulants

ABSTRACT

The National Institute for Occupational Safety and Health (NIOSH) research on direct-reading instruments (DRIs) needed an instantaneous sampling method to provide independent confirmation of the concentrations of chemical warfare agent (CWA) simulants. It was determined that evacuated canisters would be the method of choice. There is no method specifically validated for volatile organic compounds (VOCs) in the NIOSH Manual of Analytical Methods. The purpose of this study was to validate an evacuated canister method for sampling seven specific VOCs that can be used as a simulant for CWA agents (cyclohexane) or influence the DRI measurement of CWA agents (acetone, chloroform, methylene chloride, methyl ethyl ketone, hexane, and carbon tetrachloride [CCl₄]). The method used 6-L evacuated stainless-steel fused silica-lined canisters to sample the atmosphere containing VOCs. The contents of the canisters were then introduced into an autosampler/preconcentrator using a microscale purge and trap (MPT) method. The MPT method trapped and concentrated the VOCs in the air sample and removed most of the carbon dioxide and water vapor. After preconcentration, the samples were analyzed using a gas chromatograph with a mass selective detector. The method was tested, evaluated, and validated using the NIOSH recommended guidelines. The evaluation consisted of determining the optimum concentration range for the method; the sample stability over 30 days; and the accuracy, precision, and bias of the method. This method meets the NIOSH guidelines for six of the seven compounds (excluding acetone) tested in the range of 2.3–50 parts per billion (ppb), making it suitable for sampling of these VOCs at the ppb level.

IMPLICATIONS

An evacuated canister sampling and analysis method for ppb-level concentrations of VOCs simulating CWAs and possible interferents in air was developed. The analysis was conducted using a gas chromatograph with a mass selective detector. The method was validated using NIOSH guidelines. This method is useful for identifying and quantifying seven specific VOCs in the ppb range.

ACKNOWLEDGMENTS

This study was supported by NIOSH. The authors acknowledge Douglas Markle of Entech, Inc., for his assistance in setting up the preconcentration method. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of NIOSH. Mention of commercial product or trade name does not constitute endorsement by the Centers for Disease Control/NIOSH.