Identification and characterization of nitrogenous species in Brazilian petroleum by particle beam LC/MS
Analytical methodologies for the analysis of nitrogen containing compounds in a Brazilian diesel distillate by particle beam LC/MS, HPLC/UV, and GC/MS are presented. Basic and neutral nitrogen compounds are isolated by acid extraction and normal phase column chromatography. Alkylated carbazoles (C$\sb1$- to C$\sb5$-) and benzoquinolines (C$\sb2$- to C$\sb4$-) are identified as the major nitrogen components in the neutral and basic fraction, respectively. The identification is accomplished by an analytical sequence combining liquid/gas chromatography, mass spectrometry, and UV spectroscopy. Both carbazole and benzoquinoline homologues are separated by reversed phase HPLC using a C18 column. Individual isomers of carbazoles are separated by normal phase HPLC using an alumina column. The separation of individual benzoquinoline isomers is achieved by reversed phase HPLC using acidified mobiles. The identification of various types of benzoquinolines (e.g. benzo (h) quinolines, benzo (f) quinolines, and acridines) is accomplished by a combination of LC/MS and HPLC/UV spectroscopy. The quantitation of each series of carbazoles and benzoquinolines is obtained by HPLC/UV. Using the developed methods, an Arabian straight-run diesel (SRD) and a light cycle oil (LCO) are analyzed for their neutral and basic nitrogen compounds. Results are compared to those obtained from the Brazilian diesel oil.^ A unique analytical approach is also described in which normal phase (alumina) HPLC with gradient elution is used to analyze diesel oils directly without any sample preparation. Using this method, alkylated carbazoles and indoles can be measured qualitatively and quantitatively at detection limits of low mg/L (ppm) level. The potential application of this direct analysis method on a routine basis is demonstrated for the rapid identification and quantitation of neutral nitrogen compounds in diesel oils.^ To confirm the identification and characterization of nitrogen compounds by LC/MS, diesel oils are also analyzed by conventional GC/MS methods. Results are compared to those obtained by LC/MS. The advantages and disadvantages of each techniques are discussed. ^
John W. Z Mao,
"Identification and characterization of nitrogenous species in Brazilian petroleum by particle beam LC/MS"
Dissertations and Master's Theses (Campus Access).