Extraction induced by emulsion breaking for determination of Ba, Ca, Mg and Na in crude oil by inductively coupled plasma optical emission spectrometry

The selection of the sample preparation method is one of the most critical steps in the determination of metals using atomic spectrometry techniques. The aim of this paper was to propose the use of a novel strategy for crude oil sample preparation, based on the extraction induced by emulsion breaking, prior to the determination of Ba, Ca, Mg and Na by inductively coupled plasma optical emission spectrometry (ICP OES). The emulsions were prepared by mixing the crude oils samples diluted in xylene with 5% m/v Triton X-100 solution in 10% v/v HNO3. The emulsion breaking was performed by heating at 80 +/- 2 degrees C following by centrifugation to improve the separation, resulting in two distinct phases. The aqueous phase was analysed by ICP OES using inorganic standards solutions for external calibration. Ba, Ca, Mg and Na were totally extracted at a single extraction step. The limits of detection were 0.12, 1.2, 0.14 and 5.8 mu g L-1 for Ba, Ca, Mg and Na, respectively. The percentage recoveries ranged from 99 to 104% and the good agreement with the values of the certified reference material (NIST 1634c), when student-t test was applied at 95% confidence limit (p < 0.05), warranted the accuracy of the procedure. (C) 2015 Elsevier B.V. All rights reserved.