AFS Determination of Pb, As and Hg in Crude Oil with Microwave Assisted Sample Digestion

AFS was applied to the determination of Pb, As and Hg in crude oil. The sample was digested with mixed solution of HNO3-H2O2(10+2), and thiourea solution was added to the sample solution as pre-reductant and KBH4 solution (dissolved in KOH solution) as reductant. Flow-rates of 300 mL·min-1 for carrier gas and 800 mL·min-1 for shielding gas were taken in the analysis. Linear relationships between values of fluorescence intensity and mass concentration of Pb, As and Hg found were in the ranges of 2.0-80.0, 2.0-100.0 and 1.0-20.0 μg·L-1, with detection limit (3S/N) of 0.05, 0.05 and 0.01 mg·kg-1 respectively. The proposed method was applied to the analysis of samples of crude oil, giving values of recovery in the ranges of 103%-115% for Pb, 87.5%-92.1% for As and 87.5%-102% for Hg.