DETERMINATION OF TOLUENE DIISOCYANATE IN AIR USING MICRO LIQUID-CHROMATOGRAPHY WITH UV-DETECTION

A routine method using micro-LC for the determination of toluene diisocyanate (TDI) in air is presented. Air is sampled in impingers containing a toluene solution of 9-(N-methylaminomethyl)anthracene as derivatization reagent. The samples are evaporated to complete the reaction, dissolved in toluene, and shaken with buffer to remove access reagent. They are finally evaporated again, dissolved in acetonitrile/aqueous triethylamine phosphate solution and analyzed with micro-LC. The LC-system, except for the column and detector, consisted of conventional LC components. The concentration range investigated, 10-50 ng mL-1, gave correlation coefficients of 0.995 for the 2,6-TDI isomer and 0.998 for the 2,4-TDI isomer. The relative standard deviation for the method was 3.3% for 2,6-TDI and 1.5% for 2,4-TDI when analyzing solutions containing 10 ng mL-1 2,6-TDI and 20 ng mL-1 2,4-TDI (n = 15). Injection volumes of up to 200-mu-L gave a linear peak area response. The detection limits calculated for three times the chromatographic noise were 0.15 ng mL-1 for both TDI isomers when injecting 100-mu-L from a 1-mL sample. This corresponds to 0.03-mu-g m-3 with 1 L min-1 air flow through the impinger for 5 min. The detection limits were found to be better than a factor of ten lower compared to conventional LC.