Simultaneous determination of trace mercury and cadmium in tobacco samples by cold vapor generation-atomic fluorescence spectrometry

Abstract

A highly sensitive and simple method was developed for the simultaneous determination of trace cadmium and mercury in tobacco samples by cold vapor generation-atomic fluorescence spectrometry equipped with an intermittent flow reactor. The reaction was accomplished with potassium tetrahydroborate(III) in aqueous solutions. A newly modified atomizer was presented on the basis of the present atomic fluorescence system, which effectively improved the stability of the signals. Special accent was put on the study of the conditions for the generation of volatile cadmium and mercury species were investigated in detail. Some transition metal ions that could be used as sensitivity enhancers, including iron(III), cobalt(II), nickel(II), zinc(II) and molybdenum(VI) in the presence of thiourea. The tolerance to the interference of coexisting ions was carefully examined in this system. Under optimal conditions, the detection limits (3σ) were evaluated to be 2.8 ng l⁻¹ for cadmium and 4.3 ng l⁻¹ for mercury, respectively. The relative standard deviations for 10 replicate determinations of 0.8 µg l⁻¹ mercury and 1 µg l⁻¹ cadmium were 3.2% and 2.9%, respectively. The proposed method was successfully applied to the simultaneous determination of mercury and cadmium in tobacco leaf samples.