Determination of toluenediamine isomers by capillary gas chromatography and chemical ionization mass spectrometry with special reference to the biological monitoring of 2,4- and 2,6-toluene diisocyanate.

The determination of 2,3-, 3,4-, 2,6-, 2,4- and 2,5-toluenediamine (TDA) in hydrolysed human urine and blood plasma was studied by GC-MS. The TDA isomers as their perfluoro-fatty acid anhydride derivatives were investigated. Chemical ionization with ammonia and isobutane as reagent gas and monitoring both positive and negative ions are studied. Negative ion monitoring using ammonia and the TDA pentafluoropropionic anhydride (PFPA) derivatives were chosen owing to the low detection limits and good separations of the isomers studied. The ions monitored were m/z 394 and 374 corresponding to the (M-20)- and (M-40)- ions and the m/z = 397 and 377 ions of the tri-deuterium-labelled TDA used as an internal standard. The performance of 2,4-, 2,5- and 2,6-TDA-PFPA in the ion source was studied by varying the ammonia pressure, temperature and electron energy. A 1-ml volume of human urine was added to 1.5 ml of 6 M HCl containing 0.5 micrograms/l of each of the trideuterated 2,6- and 2,4-TDA and the solution was hydrolysed at 100 degrees C overnight. TDA was extracted into 2 ml of toluene by the addition of 5 ml of saturated NaOH solution. Derivatization was performed in toluene by the addition of 10 microliters of PFPA. The excesses of the reagent and acid formed were removed by extraction with 1 M phosphate buffer solution (pH 7.5). Analyses of 2,6-, 2,4- and 2,5-TDA-spiked human urine (0.2-2.5 micrograms/l) were performed. The correlation coefficients were 0.999 (n = 6). The precision (R.S.D.) for human urine spiked at 1 micrograms/l was 1.6% for 2.6-TDA, 3,5% for 2,4-TDA and 3.2% for 2,5-TDA (n = 10). The detection limit, defined as twice the signal-to-noise ratio, was 1-5 fg injected, corresponding to less than 0.05 micrograms/l of TDA in human urine or plasma.