Characterization of Organosulfur Compounds with Electrospray Ionization/Mass Spectrometry

Date

2002-08

Authors

Zhang, Yi

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Abstract

The goal of this research was to use tandem mass spectrometry (MS/MS) in an ion trap to analyze for organosulfur compounds in crude oil. Five organosulfur standard compounds were analyzed by electrospray ionization/mass spectrometry (ESIZMS) and MS/MS using PdCl<sub>2</sub> as a sensitivity enhancing reagent. Radical cations were formed by a charge transfer reaction between palladium and the sulfur compounds in the gas phase. For tandem mass spectrometry experiments, a 32 Dalton neutral loss (S) was observed for dibenzothiophene (DBT), thianthrene and benzonaphthothiophene (BNTP); and a 33 Dalton loss (HS) was observed for 2-methyl-dibenzothiophene (2-DBT) and 4,6- dimethyl-dibenzothiophene (4,6-DBT). ESI/MS and MS/MS scans were performed in both full scan and single ion monitoring (SIM) mode. Effects of some variables on the formation of molecular ions or molecular fragmentation were studied to optimize the method, including sample concentration, cone voltage, collision energy and concentration ratio between PdCl<sub>2</sub> and sulfur compounds. A standard mixture of organosulfur compounds was put in a hydrogenated white oil (Tufflo) to mimic the chemical environment of the crude oil. MS and MS/MS experiments were performed. A Maya crude oil distillate of 200-350°C was fractionated using the saturate-aromatics-resinsasphaltenes (SARA) method followed by ligand exchange chromatography in order to concentrate organosulfur components. ESIZMS and MS/MS experiments were performed on the fractions.

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Keywords

Organosulfur compounds, Petroleum, Mass spectrometry, Ionization

Citation

Zhang, Y. (2002). <i>Characterization of organosulfur compounds with electrospray ionization/mass spectrometry</i> (Unpublished thesis). Southwest Texas State University, San Marcos, Texas.

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