Sampling efficiency of a modified closed-face cassette sampler for airborne toluene diisocyanate determination

Objectives: A modified closed-face cassette was developed for sampling and derivatizing airborne toluene diisocyanate (TDI). Methods: The cassette was assembled as a regular two-piece cassette sampler except that the whole inner surface of the sampler was loaded with coated filters to ensure that all of the aspirated TDI react with 1-(2-pyridyl) piperazine (1-2pp). Results: A test atmosphere study showed that the sampling efficiencies were 89.4% and 94.3% for 2,4-TDI and 2,6-TDI. One-third of the 2,4-TDI and 2,6-TDI mass was constantly collected on the top and middle-rim filters. A polyurethane (PU)-manufacturing plant study revealed an average of 35% and 33% of both isomer masses collected on the top and middle-rim filters. The 2,4-TDI collection of the closed-face cassette sampling was 21% higher than that of open-face sampling. Furthermore, consistent isomeric compositions of airborne 2,4-/2,6-TDI obtained from both types of samplers validated the use of the modified cassette sampler. Conclusions: The closed-face cassette sampler is capable of a higher collection of airborne TDI and the technique involved is as simple and feasible as that of the open-face sampler.