Biological monitoring of hexamethylene- and isophorone-diisocyanate by the determination of hexamethylene- and isophorone-diamine in hydrolysed urine using liquid chromatography and mass spectrometry.

Hexamethylene-1,6-diamine (HDA) and isophoronediamine (IPDA) in hydrolysed human urine were studied as their perfluorofatty anhydride derivatives. Liquid chromatography and mass spectrometry with thermospray ionization were used. For quantitative analysis, the negative ions monitored were the m/z = 407 and 461, corresponding to the (M-1)- ions of the HDA-pentafluoropropionic anhydride (HDA-PFPA) and the IPDA-PFPA derivatives, respectively, and the m/z = 411 ions of the tetradeuterium-labelled HDA-PFPA (internal standard). Human urine was spiked with HDA and IPDA to six different concentrations in the range 2.5-20 micrograms l-1. Tetradeuterated HDA was used as the internal standard for the determination of both HDA and IPDA. The linear calibration curves obtained passed virtually through the origin, and the correlation coefficients were 0.998 for HDA and 0.973 for IPDA. The over-all precision for human urine spiked to a concentration of 5 micrograms l-1 of HDA and 25 micrograms l-1 of IPDA was found to be 5 and 14% (n = 5), respectively. The m/z = (M-1)- fragments, defined as twice the signal-to-noise ratio, were at the 0.5-1 pg level for the HDA and IPDA derivatives. The method presented made it possible to perform about 400 chromatographic runs during 24 h.