Desenvolvimento de metodologia para determinação de Ba, Ca, Mg e Na em amostras de petróleo por ICP OES após extração induzida por quebra de emulsão

Abstract

Nowadays, the petroleum industry needs to know the trace elements concentration in crude oil and derivatives due to the numerous problems related to its presence. This work aims the development of an appropriate procedure for determination of Ba, Ca, Mg and Na in crude oil samples by inductively coupled plasma optical emission spectrometry (ICP OES) using the emulsion breakdown induced extraction (EIBE) as sample pretreatment. This procedure is based on the formation of oil-water emulsion, using Triton X-100 in acid medium (HNO3) and mixing vigorously the samples. After, the emulsion breakdown is realized by heating. Two phases are obtained: the upper organic phase, containing just the sample, and the lower aqueous phase containing the metals extracted. The kind and concentration of surfactant (Triton X-100 e Triton X-114), the HNO3 concentration and the temperature were evaluated. The best performance was reached by mixing 0.2 g of crude oil sample with 2 mL of 5 % m/v Triton X-100 in 10 % v/v HNO3 and heating at 80º C to promove the breakdown of the emulsion. The metals were determined by ICP OES using aqueous analytical solutions for external calibration. The limits of detection reached were 0.0058, 0.062, 0.0068, 0.29 µg g-1 for Ba, Ca, Mg e Na, respectively. Recoveries values among 99.5% and 103.9% and good agreement between the informed values for Ba and Na in reference material NIST 1634c and the values obtained using the proposed procedure were reached. The good performance characteristics obtained for determination of Ba, Ca, Mg and Na in crude oil samples after the extraction using induced emulsion breakdown and ICP OES become this approach of sample pretreatment of crude oil a good alternative to the conventional procedures.