Biomarkers of toluene diisocyanate and thermal degradation products of polyurethane, with special reference to the sample preparation

The amines corresponding to 2,4- and 2,6-toluene diisocyanate (TDI) and 4,4′-methylenediphenyl diisocyanate viz. 2,4- and 2,6-toluenediamine (TDA) and 4,4′-methylenedianiline (MDA), respectively, in urine and plasma were determined under different hydrolysis conditions. The release and stability of 2,4-TDA, 2,6-TDA and 4,4′-MDA with time were studied in (A): plasma and urine from workers exposed to TDI and thermal degradation products of MDI-based polyurethane (PUR); (B) for MDI and TDI urea and urethane derivatives and (C) for 2,4-TDA, 2,6-TDA, 4,4′-MDA and trideuterated 2,4- and 2,6-TDA and dideuterated 4,4′-MDA at 100 °C, using HCl, H2SO4 and NaOH. In the biological samples an increased release of 2,4-TDA, 2,6-TDA and 4,4′-MDA with hydrolysis time was found using acidic conditions. Alkaline hydrolysis released twice more. The hydrolysis recoveries of amines, from urethane derivatives, were 20–50% with HCl and 10–20% with H2SO4 (48 h); using alkaline conditions it was 30–50% (4h). For urea derivatives, the hydrolysis recoveries of amines were 25–35% for both HC1 and H2SO4 and about 20–40% (48 h) for alkaline conditions. Losses of the free amines spiked in water and urine were observed using HCl or NaOH but much less using H2SO4. Increasing the hydrolysis time from 16 to 32 h did not result in an increase of more than 10% of the amount of amines relased. Decreasing the hydrolysis time to 8 h, decreased the amount of amines released by about 50%. Molecular sieve fractionation of plasma from workers showed that the dominating part of the biomarkers was bonded to macromolecules <10 kDa and in urine the biomarkers were bonded to molecules <5 kDa.