An Improved Inpregnated-filter Method for Measuring Low-level Concentrations fo Toluene Diiscoyanates in Air
An improved method was developed and validated for measuring low-level concentrations of toluene diisocyanates (TDIs) in air. The method is based on OSHA Method 42 for industrial applications. Airborne TDIs were trapped on a 25-mm glass-fiber filter impregnated with 50 µg of 1-(2-pyridyl)piperazine. A filter holder for was constructed to minimize contamination and losses of the analytes. The derivatized TDIs 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 C18 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 TDIs.