Simultaneous Personal Sampling of Vapor- and Aerosol-Phase TDI with a Triple Filter System
|關鍵字:||二異氰酸甲苯;雙濾紙系統;環型擴散管系統;三層濾紙系統;TDI;Dual filter system;annular denuder system;triple filter system|
There are two methods currently in use to separate gas toluence diisocyanate (TDI) from its aerosol counterpart. One is the dual filter system and the other is the annular denuder method. The former has the problem that the Teflon filter adsorbs gasous TDI resulting in an overestimation of aerosol TDI concentration. The latter is complicated in coating procedure and often bulky in size making it unsuitable as a personal sampler. To overcome these problems, a new triple filter system consisting of two Teflon filters followed by a glass fiber filter has been invented. The system allows us to estimate TDI gas adsorbed by the 1st Teflon filter hence the exact amount of vapor- and aerosol-phase TDI can be determined. According to the gas adsorption test of two Teflon filters in series, the TDI gas collection efficiency of two Teflon filters is almost the same. The results of the vaporization test using pure TDI aerosol show that it can hardly vaporize during sampling. These two findings allow us to use a simplified model to estimate accurate aerosol- and vapor-phase TDI concentrations. For size-classified sampling of aerosol- phase TDI, we added an impactor in front of the filters. It appears that using a glass fiber filter without coating as an impactor can reduce the adsorption of gasous TDI to avoid overestimation of aerosol- phase TDI. The comparison test of size-classified aerosol and gasous TDI of high humidity condition between the triple filter system and annular denuder system shows that using the triple filter system can minimize the sampling bias between dual filter system and annular denuder system. From the results, the triple filter system is proved to be superior then the dual filter system. Besides TDI, the triple filter system can also be applied to other kinds of SOCs which have low vapor pressure and do not vaporize easily during sampling.