Determination of chloride in brazilian crude oils by ion chromatography after extraction induced by emulsion breaking

• A novel strategy is proposed to the determination of chloride in crude oils.
• The extraction is based on the breaking of oil-in-water emulsions.
• Chloride was determined in the extracts by ion chromatography.
• The use of Triton X-114 in the extractant solution improved the extraction process.
• Six Brazilian crude oils were successfully analyzed using the proposed method.

The present paper reports on the development of a novel extraction induced by emulsion breaking (EIEB) method for the determination of chloride in crude oils. The proposed method was based on the formation and breaking of oil-in-water emulsions with the samples and the consequential transference of the highly water-soluble chloride to the aqueous phase during emulsion breaking, which was achieved by centrifugation. The determination of chloride in the extracts was performed by ion chromatography (IC) with conductivity detection. Several parameters (oil phase:aqueous phase ratio, crude oil:mineral oil ratio, shaking time and type and concentration of surfactant) that could affect the performance of the method were evaluated. Total extraction of chloride from samples could be achieved when 1.0 g of oil phase (0.5 g of sample + 0.5 g of mineral oil) was emulsified in 5 mL of a 2.5% (m/v) solution of Triton X-114. The obtained emulsion was shaken for 60 min and broken by centrifugation for 5 min at 5000 rpm. The separated aqueous phase was collected, filtered and diluted before analysis by IC. Under these conditions, the limit of detection was 0.5 μg g−1 NaCl and the limit of quantification was 1.6 μg g−1 NaCl. We applied the method to the determination of chloride in six Brazilian crude oils and the results did not differ statistically from those obtained by the ASTM D6470 method when the paired Student-t-test, at 95% confidence level, was applied.