Cadmium and Chromium Determination in Herbal Tinctures Employing Direct Analysis by Graphite Furnace Atomic Absorption Spectrometry (GF-AAS)

Abstract

In this study, herbal tinctures prescribed by the Brazilian public health system were analyzed for their Cd and Cr concentrations by direct analysis using electrothermal graphite furnace atomic absorption spectrometry (GF-AAS). The acidic decomposition assisted by microwave radiation was employed to evaluate the efficiency of the proposed method, demonstrating no significant differences between the methods. The accuracy of the method was evaluated obtaining adequate recoveries (106 ± 4) % for Cr and (108 ± 4) % for Cd, as well as precision regarding the repeatability with a standard deviation below 10% for both analytes. The proposed method presented limits of detection of 0.47 and 1.3 μg kg⁻¹ for Cd and Cr, respectively. No matrix effects were observed and, as a result, the external calibration curve was used, demonstrating an important advantage for the method for routine applications. Twenty-one herbal tinctures samples were evaluated, and measurable concentrations of Cd and Cr were present in some of these samples. The Cr concentration varied between 4.45 and 21.4 μg kg⁻¹, while the Cd level was from 0.76 to 40.8 μg kg⁻¹. Although these contaminant concentrations may be considered toxic to human beings, they are below the maximal limits permitted by the World Health Organization (WHO) in finished herbal products.

Keywords:

• cadmium
• chromium
• direct analysis
• herbal tinctures graphite furnace atomic absorption spectrometry (GF-AAS)

Acknowledgments

We also thank our colleagues from Faculdade de Farmácia, especially Dra. Fabíola Dutra Rocha for the herbal tinctures donation.

Additional information

Funding

We are grateful to CAPES, FAPEMIG, and CNPq for financial support.