IDENTIFICATION AND CHARACTERIZATION OF NITROGEN-COMPOUNDS IN BRAZILIAN DIESEL OIL BY PARTICLE-BEAM IC-MS

A simple procedure has been developed to isolate the basic and neutral nitrogen compounds from a Brazilian diesel distillate through acid pa rtition and open column chromatography using alumina. With minimum sam ple preparation and clean-up, isolated fractions were analysed by part icle beam liquid chromatography-mass spectrometry (l.c.-m.s.) using bo th reversed phase and normal phase chromatography. The basic fraction was found to contain mostly alkyl benzoquinolines (C-2-C-4). The neutr al fraction contained mostly alkyl carbazoles (C-1-C-5). The identific ation was based upon electron impact mass spectra of each class of nit rogen compounds, and confirmed by ultraviolet (u.v.) spectral characte ristics obtained using online photodiode array detection. Reversed pha se chromatography was found to be more appropriate for resolving each class of carbazoles and benzoquinolines, while normal phase chromatogr aphy was superior for separating individual isomers. The quantitation of each class of carbazoles and benzoquinolines was obtained by high p erformance liquid chromatography-ultraviolet (h.p.l.c.-u.v.) analysis at 254 nm using carbazole and benzo[h]quinoline as calibration standar ds. Comparison of the Brazilian diesel distillate to diesels having ot her origins indicated that they were nearly identical in terms of the nitrogen compounds present.