| Objective To establish a method for simultaneous determination of lead and arsenic ,cadmium and mercury in food samples by atomic fluorescence spectrometry. Method Microwave-digestion technique using HNO3-H2O2 was applied for the pretreatment of samples. The instrumental operation parameters such as electrical currents of lamp, negative voltage of photoelectric multiplier tube (PMT), height of atomic oven , flow of carrier gas and shield gas which affect the determination had been optimized. The experimental reaction systems were improved and reaction conditions such as concentrations of KBH4, K3Fe(CN)6, Co2+,thiourea-ascorbic acid and HCl in the reaction medium were optimized, respectively. The influence from co-exist foreign ions and the elimination were also studied. Results Under the optimized conditions, the detection limit of lead was 0.065μg/L , 0.053μg/L for arsenic, 0.0065μg/L for cadmium and 0.032μg/L for mercury. The quantification limits were 0.22μg/L for lead, 0.18μg/L for arsenic , 0.022μg/L for cadmium and 0.10μg/L for mercury, respectively. the linear ranges of lead and assenic were from quantification limits to 10μg/L and the correlation coefficient was more than 0.9998. The relative standard deviation (RSD) were in the range from 0.7% to 2.7%. The linear ranges of cadmium and mercury were from quantification limits to 4.0μg/L and the correlation coefficients were from 0.9994 to 0.9999. The RSD of the analytical methods were in the range of 1.0%～5.07 % .The spiked recoveries were 88.8%～107.8% for lead, 93.8～102.5% for arsenic ,the cadmium was from 97.0% to 119.5%, and the mercury was from 88.5 to 104.0%. Trace lead and arsenic in the standard reference substance (GBW08571) were also determined by the proposed method and the results were in good agreement with recommended value. Conclusions The method is simple, rapid, accurate and sensitive. It can be adopted for simultaneous determination of lead and arsenic ,cadmium and mercury in food samples.
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