Microwave-Assisted Extraction of Chloride Followed by Ion Chromatography as an Alternative to the ASTM D6470 Method for the Determination of Crude Oil Salinity

The presence of chloride in crude oil can result in a number of drawbacks, with technical and economic impacts on the production of petroleum derivatives. For this reason, it must be carefully monitored in this kind of sample. In this work, we developed a simple and efficient method for the determination of chloride in crude oil by ion chromatography with conductivity detection after microwave-assisted extraction. The method was optimized using a multivariate strategy based on the use of a two-level full factorial design for the screening of significant factors and a Doehlert matrix for their optimization. Four factors were selected in this study: mass of the sample, extraction temperature, extraction time, and the volume of toluene employed to disperse the sample. Under optimized conditions, 1.10 g of the sample was dispersed in 3.0 mL of toluene and 10 mL of deionized water was added. The mixture was irradiated for 25 min at 146 degrees C (extraction temperature). After cooling, the mixture was centrifuged for 15 min at 5000 rpm for separation of the phases, and the aqueous extract was filtered and analyzed by ion chromatography. The limits of detection and quantification of the method were 0.13 and 0.39 mu g g(-1), respectively. The method was applied in the determination of chloride in four samples of crude oil, and the obtained results were statistically similar to those obtained by the reference method (ASTM D6470).