Determination of Cd and Pb in medicinal plants using solid sampling flame atomic absorption spectrometry

Abstract

A procedure for trace determination of Cd and Pb in medicinal samples using solid sampling flame atomic absorption spectrometry (SS-F AAS) was developed for trace determination of Cd and Pb in medicinal plants. Powdered samples were mixed with high purity graphite and introduced as pellets (up to 100 mg) into a quartz device positioned above the burner and heated by air–acetylene flame. Oxygen flowing through the quartz device assure the complete combustion of sample. Combustion was started in 2 s after sample introduction and the produced vapours were subsequently dispersed into the flame. Calibration was performed using different masses of solid certified reference material (for Pb) or with reference solutions applied directly on graphite pellets (for Cd). Integrated absorbance mode was used and signals were integrated in less than 10 s. A deuterium background corrector was used throughout. Characteristic masses were 58 and 790 pg for Cd and Pb, respectively. Accuracy was checked using certified reference materials and the percent relative error was between −7 and 2% for Cd and between −2 and 3% for Pb. Relative standard deviations (repeatability) were always below 10% (n = 5). Limits of detection were 0.012 and 0.10 µg g−1 for Cd and Pb, respectively. The proposed procedure by SS-F AAS is simple and may be applied to conventional atomic spectrometers allowing the determination of Cd or Pb in 40 test samples by hour (excluding the steps for sample preparation).