Fast emulsion-based method for simultaneous determination of Co, Cu, Pb and Se in crude oil, gasoline and diesel by graphite furnace atomic absorption spectrometry

A method for the simultaneous determination of Co, Cu, Pb and Se in crude oil, gasoline and diesel samples using emulsion-based sampling and GF AAS is proposed. 400 mg of sample was weighted in volumetric flask following the sequential addition of 125 mu L of hexane and 7.5 mL of Triton X-1000 (R) (20% m v(-1)). Subsequently, the mixture was stirred in ultrasonic bath, during 30 min, before dilution to 25 mL with deionized water. Aliquots of 20 mu L of reference solution or sample emulsion were co-injected into the graphite tube with 10 mu L of 2 g L-1 Pd(NO3)(2). The pyrolysis and atomization temperatures were 1300 degrees C and 2250 degrees C, respectively. The limits of detection (n=10, 3 sigma) and characteristic masses were 0.02 mu g g(-1) (0.32 mu g L-1) and 18 pg for Co, 0.03 mu g g(-1) (0.48 mu g L-1) and 15 pg for Cu, 0.04 mu g g(-1) (0.64 mu g L-1) and 48 pg for Pb, and 0.11 mu g g(-1) (1.76 mu g L-1) and 47 pg for Se. The reliabilities of the proposed method for Co and Se were checked by SRM (R) 1634c Residual Oil analysis. The found values are in accordance to the SRM at 95% confidence level (Student's t-test). Each sample was spiked with 0.18 mu g g(-1) of Co, Cu, Pb and Se and the recoveries varied from 92% to 116% for Co, 83% to 117% for Cu, 72% to 117% for Pb, and 82% to 122% for Se. (C) 2013 Published by Elsevier B.V.