A Gas Chromatographic Procedure for the Determination of Airborne MDI and TDI

A method is described for the analysis of airborne diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI) using gas-liquid chromatography. The diisocyanates are collected in acidic absorbing solution where they undergo hydrolysis, converted to the free diamines with caustic, and extracted into toluene. The diamines are derivatized in the toluene with heptafluorobutyric anhydride (HFBA). These derivatives are analyzed by GLC using an electron capture detector. The method has the advantages of specificity for the two diisocyanates, while demonstrating excellent accuracy and precision. A value one-tenth of the NIOSH recommended Occupational Health Standard for either compound may easily be detected in a 40 liter air sample.