Biological monitoring of hexamethylene diisocyanate by determination of 1,6-hexamethylene diamine as the trifluoroethyl chloroformate derivative using capillary gas chromatography with thermoionic and selective-ion monitoring.

A GC method using a novel derivatization reagent, 2',2',2-trifluoroethyl chloroformate (TFECF), for the derivatization of primary and secondary aliphatic amines with the formation of carbamate esters is presented. The method is based on a derivatization procedure in a two-phase system, where the carbamate ester is formed. The method is applied to the determination of 1,6-hexamethylene diamine (HDA) in aqueous solutions and human urine, using capillary GC. Detection was performed using thermionic specific detection (TSD) and mass spectrometry (MS)-selective-ion monitoring (SIM) using electron-impact (EI) and chemical ionization (CI) with ammonia monitoring both positive (CI)+ and negative ions (CI)-. Quantitative measurements were made in the chemical ionization mode monitoring both positive and negative ions. Tetra-deuterium-labelled HDA (TDHDA; H2NC2H2(CH2)4C2H2NH2) was used as the internal standard for the GC-MS analysis. In CI+ the m/z 386 and the m/z 390 ions corresponding to the [M + 18]+ ions (M = molecular ion) of HDA-TFECF and TDHDA-TFECF were measured; in CI- the m/z 267 and the m/z 271 ions corresponding to the [M - 101]- ions. The overall recovery was found to be 97 +/- 5% for a HDA concentration of 1000 micrograms/l in urine. The minimal detectable concentration in urine was found to be less than 20 micrograms/l using GC-TSD and 0.5 micrograms/l using GC-SIM. The overall precision for the work-up procedure and GC analysis was ca. 3% (n = 5) for 1000 micrograms/l HDA-spiked urine, and ca. 4% (n = 5) for 100 micrograms/l. The precision using GC-SIM for urine samples spiked to a concentration of 5 micrograms/l was found to be 6.3% (n = 10).