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 µL of hexane and 7.5 mL of Triton X-100® (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 μL of reference solution or sample emulsion were co-injected into the graphite tube with 10 μL of 2 g L−1 Pd(NO3)2. The pyrolysis and atomization temperatures were 1300 °C and 2250 °C, respectively. The limits of detection (n=10, 3σ) and characteristic masses were 0.02 μg g−1 (0.32 μg L-1) and 18 pg for Co, 0.03 μg g−1 (0.48 μg L−1) and 15 pg for Cu, 0.04 μg g−1 (0.64 μg L−1) and 48 pg for Pb, and 0.11 μg g−1 (1.76 μg L−1) and 47 pg for Se. The reliabilities of the proposed method for Co and Se were checked by SRM® 1634c Residual Oil analysis. The found values are in accordance to the SRM at 95% confidence level (Studentʹs t-test). Each sample was spiked with 0.18 μg 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.