Journal of Chromatography A, 824 (1998) 45–52 Bacterial sulfate production by biodesulfurization of aromatic 1 hydrocarbons, determined by ion chromatography a, b a b c * ´ ´ Luz M. Soto , Hilda Ledo , Yaritza Calderon , Julio Marın , Federico Galarraga a ´ ´ ´ Laboratorio de Ecologıa Microbiana y Biotecnologıa, Departamento de Biologıa – Facultad de Ciencias, Universidad del Zulia, Maracaibo, Venezuela b ´ ´ Laboratorio de Quımica Ambiental, Departamento de Quımica – Facultad de Ciencias, Universidad del Zulia, Maracaibo, Venezuela c Instituto de Ciencias de la Tierra, Facultad de Ciencias, Universidad Central de Venezuela, Caracas, Venezuela Received 13 April 1998; received in revised form 7 July 1998; accepted 15 July 1998 Abstract The use of bacteria to remove sulfur from crude oil or petroleum distillates is a novel concept that presents an alternative biotechnology to the current technology of hydrodesulfurization (HDS). Sulfur must be removed from crude oils prior use. The burning of fossil fuels containing sulfur releases sulfur dioxide into the atmosphere causing acid rain. The aim of this work is to determine the sulfate concentration by ion chromatography (IC), and calculate the percentage of transformation of organic bound sulfur, that is converted to sulfate, and estimate the efficiency of bacteria in desulfurization. IC is a suitable method for sulfate concentration determination. However, when chloride concentrations are significantly high, interference of the sulfate signal does occur. In this case, it could be avoided by diluting samples. A Dionex Model 2000i / SP IC system, with an anionic pre-column (Dionex AG4A), an anion separator column (Dionex AS4A), a suppresor column (Dionex AMMS-II), and a conductivity detector was used. The eluent (21 mM NaOH) and regenerant (electrolyzed 18 MV /cm water) flow-rates were 1.0 and 2.0 ml/min, respectively. The sample loop volume was 10 ml and the conductivity sensitivity was 30 mS. The diluted samples were filtered through a 0.45-mm filter before injection. The highest sulfate concentration detected was 24.10 mg / l, corresponding to a maximal conversion rate of 10% in a month. Sulfate ions were not detected in control samples. The correlation coefficient for a linear least squares fit was 0.99 ( p,0.001). The minimal concentration that we can read was 0.02 mg / l and this concentration corresponded to the limit of detection obtained under the conditions employed in this study. IC is an economical, sensitive and accurate way to estimate the sulfate concentrations in microbiological samples.  1998 Elsevier Science B.V. All rights reserved. Keywords: Petroleum; Oils; Dibenzothiophene; Sulfur compounds; Thianthrene; Sulfates; Hydrocarbons, aromatic 1. Introduction bitumen. A variety of sulfur-containing organic compounds are found in fossil fuels. Heavy oils and Petroleum contains sulfur compounds that repre- bitumens contain 3 to 6% sulfur. Most of the sulfur sent the predominant species in heavy oils, such as present in heavy oils is organically bound, and is found in structures such as thiol, sulfide, disulfide, * Corresponding author. Corresponding address: Apdo 15299, thiophenic forms, substituted benzothiophenes and Zona Postal 4005-A, Las Delicias, Maracaibo, Venezuela. 1 dibenzothiophenes and more complex molecules like Presented at the International Ion Chromatography Symposium 1997, Santa Clara, CA, 14–17 September 1997. thianthrene [1]. 0021-9673 / 98 / $ – see front matter  1998 Elsevier Science B.V. All rights reserved. PII: S0021-9673(98)00583-4