A Novel Personal Air Sampling Device for Collecting Volatile Organic Compounds: A Comparison to Charcoal Tubes and Diffusive Badges

Abstract

Evacuated canisters have been used for many years to collect ambient air samples for gases and vapors. Recently, significant interest has arisen in using evacuated canisters for personal breathing zone sampling as an alternative to sorbent sampling. A novel flow control device was designed and built at McGill University. The flow control device was designed to provide a very low flow rate, < 0.5 mL/min, to allow a sample to be collected over an extended period of time. Previous experiments run at McGill have shown agreement between the mathematical and empirical models to predict flow rate. The flow control device combined with an evacuated canister (capillary flow control-canister) was used in a series of experiments to evaluate its performance against charcoal tubes and diffusive badges. Air samples of six volatile organic compounds were simultaneously collected in a chamber using the capillary flow control-canister, charcoal tubes, and diffusive badges. Five different concentrations of the six volatile organic compounds were evaluated. The results from the three sampling devices were compared to each other and to concentration values obtained using an online gas chromatograph (GC). Eighty-four samples of each method were collected for each of the six chemicals. Results indicate that the capillary flow control-canister device compares quite favorably to the online GC and to the charcoal tubes, p > 0.05 for most of the tests. The capillary flow control-canister was found to be more accurate for the compounds evaluated, easier to use, and easier to analyze than charcoal tubes and passive dosimeter badges.

Keywords:

• personal air sampling
• canisters
• charcoal tubes
• diffusive badges

Notes

^A Desorption efficiency for charcoal tubes and badges, n = 10 at 0.5 and 1 TLV

^B Canister recovery was based on n = 36 for each compound

^A GC Ref. is the reference concentration established at the time of sampling using an online gas chromatograph, n (∼ n = 25 to 30).

^B Relative humidity levels: Tests 1 to 6 = < 5%; 7 to 12 = 50%; 13 = 80%; 14 = 90%.

^C Temperature was held constant for all tests at 24.6 ± 0.4°C.

^D Statistical difference observed between online GC and capillary-canisters using a t-test, p < 0.05.

^E Co-elution between MEK and Ethyl acetate resulted in quantification difficulties for the charcoal tubes.

^F Statistical difference observed between capillary-canister and charcoal tubes using a t-test, p < 0.05.

^A Mean values for the 14 tests shown in Table II