Simultaneous determination of trimellitic anhydride and its trimellitic acid impurity by GC/FID.

Trimellitic anhydride has widespread usage in a variety of industrial processes. Inhalation of the airborne dust and fumes generated by these processes is the primary route of occupational exposure leading to a variety of respiratory maladies. Because of its extensive industrial usage and limited toxicological data, trimellitic anhydride was scheduled for toxicological evaluation. Analytical purity certification and chemical characterization of the chemical were required as prerequisites for such toxicological tests. Therefore, a sensitive and specific procedure for the analysis of trimellitic anhydride and its trimellitic acid impurity in admixture was developed. After methylation with diazomethane, the compounds were assayed by gas chromatography using flame ionization detection. Chromatography on 5% SP-2100 yielded two well separated peaks, which were used for quantitation of the parent compounds. Confirmational identity of trimellitic anhydride was determined by direct insertion probe mass spectrometry, while that of the anhydride methyl derivative and trimellitic acid trimethyl derivative was determined by gas chromatography-mass spectrometry.