| Summary: | The present paper reports a new application: the voltammetric determination in herbal medicines of ultra-trace thallium(I), in the presence of lead(II), tin(II) and antimony(III) as interfering metals, by square wave anodic stripping voltammetry (SWASV). A conventional three-electrodes voltammetric cell was employed with a stationary hanging mercury drop electrode (HMDE) as working electrode and a platinum electrode and an Ag|AgCl|KCl<sub>satd.</sub> electrode as auxiliary and reference electrodes, respectively. The supporting electrolyte was 0.5 mol L<sup>−1</sup> ammonium citrate buffer pH 6.5 + 7.3·10<sup>−3</sup> mol L<sup>−1</sup> EDTA-Na<sub>2</sub>. The analytical procedure was verified by the analysis of the standard reference materials: spinach Leaves NIST-SRM 1570a and tomato leaves NIST-SRM 1573a from National Institute of Standards and Technology. Precision and trueness, expressed as relative standard deviation and relative error, respectively, were generally lower than 7% in all cases. Once set up on the standard reference materials, the analytical procedure was transferred and applied to herbal medicines samples—<i>Taraxacun officinale weber</i>, <i>Eucalyptus globulus</i> and <i>Harpagophytum procumbens DC</i>—sold on the market. A critical comparison with spectroscopic measurements is also discussed.
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