Generation and Evaluation of Reference Samples as Part of an Evacuated Canister Interlaboratory Study

Air Methods, Monitoring, and Technology - Session 2
Oral Presentation

Prepared by , R. LeBouf

Contact Information: DABurns@cdc.gov; 304-285-5756


ABSTRACT

Evacuated canisters offer an opportunity to expand on the way volatile organic compounds (VOCs) are measured in indoor air quality investigations, industrial hygiene assessments, and emergency response scenarios. There is a need for alternative sampling methods for VOCs as traditional sorbent tube sampling methods may not adequately capture the multitude of chemicals present in mixed exposure environments due to sorbent-analyte specificity. This study is part of a larger work designed to address this need across a suite of 17 VOCs. This study assesses generation and evaluation methods for the production of reference evacuated canister samples as part of an interlaboratory study.

The reference canister samples were generated in two concentration ranges (PPM and PPB) and at three nominal concentration levels within the two ranges. For the PPB range, samples were generated using either a flow-based dilution or combination pressure dilution and canister-to-canister transfer technique. For the PPM range, samples were generated by either the combination pressure dilution and canister-to-canister transfer technique, or a manifold dilution method. The reference canister samples were analyzed via a preconcentrator/gas chromatography-mass spectrometer system. The performance of three preparation methods and three analytical methods were assessed using the NIOSH accuracy criterion.

All 17 VOCs passed the NIOSH accuracy criterion for the PPM range when prepared using the pressure dilution technique and analyzed via a 1 cc loop injection. For the PPB range of concentration levels, 15 VOCs passed the NIOSH accuracy criterion when prepared by the pressure dilution method and analyzed via a 250 cc injection.

Method accuracy is concentration dependent with respect to certain combinations of analytical method, preparation technique, and analyte. Some sample preparation techniques were found to be better for certain groups of compounds and at certain concentration ranges. The preparation of canister standards and spike generation as well as the manner in which they are introduced into the analysis system affects method performance.