Determination of gaseous toluene diisocyanate by use of solid-phase micoextraction with on-fibre derivatisation

An SPME method was developed for sampling ng gaseous 2,4-toluene diisocyana te (2,4-TDI) involving derivatisation of the isocyanate by reacting with di butylamine (DBA). The TDI-DBA derivative thus formed was determined by LC-M S-MS utilising atmospheric pressure chemical ionisation (APCI). As a first step, DBA was loaded onto a poly(dimethylsiloxane)/divinylbenzene (PDMS-DVB ) fibre coating by direct vapour-phase extraction of a highly concentrated diethyl ether solution of DBA. The DBA-loaded fibre was then exposed to an artificially generated atmosphere of gaseous 2,4-TDI. The linearity of the method ranged from 52.8 to 3100 mug m(-3) (6.8 to 400 ppbv) with a sampling time of 60 min. The proposed method has been applied to 2,4-TDI determinat ion in an artificially generated dynamic standard atmosphere, yielding an a pproximate method detection limit (MDL) of 2 mug m(-3) (0.25 ppbv). This co ncentration is one twentieth of the Occupational Safety and Health Administ ration (OSHA) 8-hour time-weighted average (TWA) exposure limit. The sample r with the PDMS-DVB-DBA coating was found to be stable and retains the requ ired amount of DBA for at least 10 days, an important feature for sampling systems with potential in-situ applications.