Trisaminohexyl isocyanurate, a urinary biomarker of HDI isocyanurate exposure

Biological monitoring of occupational exposure to 1,6-hexamethylene diisocyanate (HDI)-containing spray-paints is limited to analysis of metabolites of HDI monomer although polymeric HDI isocyanurate constitutes the predominant inhalation and skin exposure for workers in the automotive paint industry. A novel method using nanoflow ultra-performance liquid chromatography coupled to nano-electrospray ionization tandem mass spectrometry (nano-UPLC-ESI-MS/MS) was developed to quantify trisaminohexyl isocyanurate (TAHI), a hydrolysis product of HDI isocyanurate, in the urine of spray-painters. Analytical and internal standards were synthesized in-house and weighted linear regression calibration curves were generated using spiked control urine from non-exposed persons (0.06-7.98 μg/L; N = 13; w = x−2; r = 0.998). Urine samples collected from 15 exposed workers (N = 111) were subjected to acid hydrolysis and extracted with dichloromethane, then derivatized with acetic anhydride. The derivatized product, trisacetamidohexyl isocyanurate (TAAHI), was analyzed using nano-UPLC-ESI-MS/MS. The protocol was sensitive and specific for analysis of TAHI in the urine of exposed workers with a method detection limit at 0.03 μg/L. TAHI was detected in 33 of 111 urine samples and in 11 of 15 workers. This biomarker for HDI isocyanurate is critical to determine the relative potency and dose-relationships between the monomer and oligomer exposure on the development of diisocyanate induced health effects in future studies.