Simultaneous Sampling of Gas- and Aerosol-Phase TDI with a Triple Filter System

Abstract

A new triple filter system sampler/model is proposed for the precise and accurate simultaneous sampling and determination of gas-and aerosol-phase 2,4-toluene diisocyanate (TDI). The system consists of two front Teflon filters for sampling aerosol-phase TDI and a final coated glass fiber filter to collect gas-phase TDI. The aerosolphase TDI is collected on the first Teflon filter, while the second Teflon filter is used to estimate gaseous TDI adsorbed by the first. According to the gas adsorption test of two Teflon filters in series, the TDI gas adsorption fraction of the two filters is almost the same. Results of the evaporation test using pure TDI aerosols collected on the Teflon filter show that significant evaporation of the compound does not occur during sampling. These two findings allow the use of a model to estimate accurate gasand aerosol-phase TDI concentrations. The comparison test with an annular denuder shows that the triple filter system can minimize the TDI sampling bias between the dual filter and the annular denuder systems.

Measurement of 2,4-toluene diisocyanate concentrations by different samplers

“…The first Teflon filter is to collect aerosol-phase TDI, while the second is to calibrate the gas-phase TDI adsorbed by the first Teflon filter using the model of the triple filter system [16]. The GFF is used to collect the remaining gas-phase TDI.…”

“…The TFS sampler was designed previously [16] which consists of three filters: two 37-mm, 2.0-m Teflon filters (Zefluor TM , PTFE, Pall Co., Ann Arbor, MI, USA) in series followed by a 1.0-m, 37-mm GFF (type A/E, SKC Inc., Eighty Four, PA, USA) coated with 1 mg of 1-2PP according to the OSHA 42 [9]. The first Teflon filter is to collect aerosol-phase TDI, while the second is to calibrate the gas-phase TDI adsorbed by the first Teflon filter using the model of the triple filter system [16].…”

“…The laboratory test with sampling time of 15 min showed that the TFS is in good agreement with the reference ADS both in the gaseous and aerosol TDI concentrations [16]. The overestimation of the aerosol TDI concentration and underestimation of the gaseous TDI concentration in case of the DFS are minimized.…”

“…The coating and extraction procedure of the annular denuder system is somewhat complicated. The triple filter system (TFS) using two front uncoated Teflon filters and one coated GFF in series, was tested in the laboratory together with the ADS and DFS for simultaneous sampling of gaseous and aerosol TDI [16]. A model was developed to calculate the accurate amount of gaseous and aerosol TDI using the amount of TDI collected by each of the three filters.…”

Occupational Health Research in Taiwan.

“…A new triple filter system has also been developed to simultaneously separate and collect the vaporous and aerosol phases of toluene diisocyanate exposed in spray painting and polyurethane foam manufacturing operations 54) . Other studies examining the effects of environmental conditions and electrical charges on the weighing accuracy of different filter materials, the performance of commercial aerosol number samplers and direct reading aerosol monitors, and the error due to masking effect in fiber counting and bio-aerosol colony counting have also been conducted [55][56][57][58][59][60] . These invention and scientific findings in aerosol sampling shed light in the correct relationship between aerosol exposure and health effects.…”