Determination of Lead in Tea Garden Soil by Hydride Generation Atomic Fluorescence Spectrometry with Microwave Digestion

The microwave digestion system with aqua regia was developed for the determination of trace lead in tea garden soil using Hydride Generation-Atomic Fluorescence Spectrometry (HG-AFS). The leaching methods, experimental conditions, booster and coexisting element were optimized. The largest amount of lead was leached out by microwave digestion with aqua regia, which has the advantages of less usage of reagent and less environmental pollution. An appropriate amount of potassium ferricyanide and hydroxylamine hydrochloride improved the hydride generation efficiency of Pb. The lead blank was reduced significantly when Potassium ferricyanide solution was treated with rice husk to remove Pb in the reagent. It was found that Co, Zn, As, and Cd did not interfere with the determination of lead. The addition of 1,10-phenanthroline monohydrate and sodium hydrosulfide could effectively eliminate the interferences from Fe and Cu, which improved the recovery rate of lead. The limit of detection was 0.65 μg/L and the precision was 1.89% (n=10) with recoveries of 86.8%-110.4% for Pb. The reliability of the method has been tested by determination of Pb in the Soils Standard Reference Materials and the results are in agreement with the certified values. The method has been applied to the determination of Pb in tea garden soil with satisfactory results. It was also particularly suitable for large batches of samples.