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

Abstract

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; H 2NC 2H 2(CH 2) 4C 2H 2NH 2) 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 μg/l in urine. The minimal detectable concentration in urine was found to be less than 20 μg/l using GC—TSD and 0.5 μg/l using GC—SIM. The overall precision for the work-up procedure and GC analysis was ca. 3% ( n = 5) for 1000 μg/l HDA-spiked urine, and ca. 4% ( n = 5) for 100 μg/l. The precision using GC—SIM for urine samples spiked to a concentration of 5 μg/l was found to be 6.3% ( n = 10).