Determination of toluene diisocyanate in air by HPLC and band-tape monitors

Abstract

An improved HPLC method was developed for determining the atmospheric concentration of toluene diisocyanate (TDI). 1-(2-pyridyl)-piperazine in toluene was used as reagent absorber solution together with reversed phase chromatography and a simple efficient buffer system (0.1% trifluoroacetic acid--acetonitrile, 85:15%) in an isocratic elution mode. The values for atmospheric TDI concentration obtained with two continuous band-tape monitors were checked using the values from HPLC as reference. Under identical experimental conditions the two instruments (both model 7005) gave readings varying by more than 100%. At low humidity the band-tape values were considerably lower than the HPLC values. At an absolute humidity of 11.7 g H2O/m3 (58% relative humidity) the value from instrument 1, but not instrument 2, agreed with those from HPLC. The values obtained with band-tape devices in the continuous monitoring of TDI concentration in places of work, or epidemiological studies, should be assessed with caution. HPLC offers a useful reference method for monitoring the accuracy of such devices.