An improved high pressure liquid chromatographic method for the determination of isocyanates using "nitro reagent"

The chromatographic problems associated with the excess derivatizing reagent, N-4-nitrobenzyl-N-n-propylamine, in the commonly used HPLC method for the determination of isocyanates have been eliminated. An aqueous extraction removed the excess reagent without affecting the concentration of the urea derivatives. The combination of the extraction with the use of a fast-LC column allowed separation and quantitation of 4,4'-diphenylmethane diisocyanate, 2,4- and 2,6-toluene diisocyanate and hexamethylene diisocyanate within four minutes under isocratic conditions. Detection limits ranged from 2 to 5 ng injected.