An Improved Impregnated-Filter Method for Measuring Low-Level Concentrations of Toluene Diisocyanates in Air

An improved method was developed and validated for measuring low-level concentrations of toluene diisocyanates (TDls) in air. The method is based on OSHA Method 42 for industrial applications. Airborne TDls were trapped on a 25-mm glass-fiber filter impregnated with 50 pg of 1-(2pyridy1)piperazine. A filter holder for was constructed to minimize contamination and losses of the analytes. The derivatized TDls were extracted by immersion of the filter in a small volume of solvent. The analysis was performed with a high performance liquid chromatograph equipped with a fluorescence detector and a CIB base-deactivated silica column. The modified method has a lower limit of quantitation of 0.02 ppb in 15 L of air for both 2,4-toluene diisocyanate (2,4-TDI) and 2,6-toluene diisocyanate (2,6-TDI), which is about a fifteen-fold enhancement over Method 42. The recovery efficiencies and 95% confidence intervals for vapor-spiked filters were 77 + 6 percent for 2,4-TDI and 69 + 10 percent for 2,6-TDI. The precision of replicate analyses was ten percent or better. The method was used to screen flexible polyurethane foam for emissions of unreacted TDls.