Determination of lead and cadmium in oregano, laurel, thyme, green tea and tobacco by flame atomic adsorption spectroscopy using ZnO nanoflowers

Abstract

Cd and Pb are toxic heavy metals present in various samples, including oregano, laurel, thyme, green tea and tobacco. Exposure to these metals poses significant health risks, making regular monitoring essential. In this study, an efficient method was developed for the quantification of Pb and Cd in these herbs and in cigarette tobacco by flame atomic absorption spectroscopy (FAAS) employing ZnO nanoflowers as preconcentration material. The ZnO nanoflowers were synthesized via a solvothermal method and characterized by SEM, EDS, XRD and BET techniques, exhibiting a nanoplate morphology with a surface area of 9.8 m² g⁻¹. Extraction process was optimized using a Taguchi L₉(3³) design, achieving extraction efficiencies of 99.20 % for Pb and 59.35 % for Cd. The preconcentration process yielded enrichment factors of 9.7 and 5.8 for Pb and Cd, respectively. The proposed methodology was validated, demonstrating high accuracy and precision. Metal concentrations in the aforementioned herbs ranged from 0.37 to 18.87 µg g⁻¹ for Pb and from 0.48 to 2.79 µg g⁻¹ for Cd, and for tobacco from 0.73 to 18.87 µg g⁻¹ for Pb and 0.69–1.41 for Cd. This method provides a reliable and cost-effective alternative for monitoring Pb and Cd in herbs and their derived products.