EVALUATION OF CHROMATOGRAPHIC METHODS FOR THE DETERMINATION OF ISOCYANATES IN AIR

Chromatographic methods for the determination of toluene diisocyanates (TDI) in air, at concentrations of 20–40 μg/m3, were evaluated. Test atmospheres were generated by a gas-phase permeation principle. The GC method was based on sampling in impingers containing an acidic aqueous solution (0.4 MHCI) where the isocyanates are hydrolysed into the corresponding amines. The pentafluoropropionic acid derivatives of the amines were analysed using glass capillary GC with thermionic detection. The HPLC methods were based on reaction with the amine reagents 9-(N-methylaminomethyl)-anthracene (1Xl0-4Min toluene) and l-(2-methoxyphenyl)-piperazine (2Xl0-4Min toluene). The urea derivatives were determined using UV detection. The sampling efficiency for gaseous TDI with toluene as absorbing solution was 97%. Sampling efficiencies in various acidic aqueous solutions were 83-88%. The relative standard deviation for the various methods was ca. 6%. No sampling losses for TDI, due to influences of interfering substances (diethylamine, dimethylethylamine, N-methylmorpholine, DABCO, aniline, ethanol, phenol) using acidic aqueous 0.4 M HCI were obtained. Diethylamine, N-methylmorpholine and DABCO affected the analytical results when toluene solutions of the amine reagents MAMA and MPP were used. © 1990, Taylor & Francis Group, LLC. All rights reserved.