Determination of lead in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry using direct solid sampling

A procedure is proposed for Pb determination in medicinal plants by high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GF AAS) using direct solid sampling. Among Pd(NO3)2, Pd/Mg(NO3)2, NH4H2PO4 and the W-coated platform tested as chemical modifiers, Pd(NO3)2 presented the best performance. Calibration plots (10–1000pg Pb) with regression coefficients better than 0.999 were typically obtained. Accuracy was checked for Pb determination in five plant certified reference materials. Results were in agreement with reference values at a 95% confidence level (paired t-test). Medicinal plant samples were analyzed by the proposed procedure and line-source GF AAS using slurry sampling as a comparative technique. The RSD was 10% (n=3) for a sample containing 0.88μgg−1 Pb. The limit of quantification (dry mass) was 0.024μgg−1. The contents of Pb in medicinal plant samples varied in the 0.30–1.94μgg−1 range. ► Direct solid sampling is proposed for Pb determination in plants by HR-CS GF AAS. ► Optimization of various modifiers for solid sampling and aqueous calibration. ► Evaluation of homogeneity and sample mass size for ultra-microanalysis. ► A sustainable clean analytical method was developed for medicinal plant analysis.