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Graphite Furnace Atomic Absorption Spectrophotometry (GFAAS) method was developed and validated for the determination of arsenic (As), lead (Pb) and cadmium (Cd) in herbal medicines. Samples were prepared by wet digestion. Validation was performed according to the International
Committee on Harmonization (ICH) Guidelines. The proposed method permitted the determination of As, Pb and Cd in the ranges of 5-80 ng/ml, 10-80 ng/ml and 0.25-4.0 ng/ml, respectively, with correlation coefficients greater than 0.999. Limit of detection (LOD) were found to be 2.5 ng/ml, 2.5 ng/ml and 0.16 ng/ml for As, Pb and Cd, respectively, while limit of quantitation (LOQ) were found to be 1 μg/g, 2 μg/g and 0.1 μg/g for As, Pb and Cd, respectively. Mean percentage recoveries were in the range of 98.8-105.6 while intra- and inter-day precisions were less than 4.7% for all three heavy metals. The method was successfully applied to the study of heavy metal contamination in herbal medicines available in Thailand. A total of 86 samples were investigated and the results showed that all test samples contained As, Pb and Cd lower than the limit specified in the Thai Herbal Pharmacopoeia.

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