Direct multi-element analysis of natural toothbrush by electrothermal vaporization into inductively coupled plasma optical emission spectrometry

Abstract

To address the lack of information on the concentrations of potentially toxic and essential elements in natural toothbrush, well known as miswak, a fast screening multi-element analysis method was developed using electrothermal vaporization (ETV) into inductively coupled plasma optical emission spectrometry (ICPOES). The following ranges of total concentrations were measured in commercially available miswak: Cu (1.3–1.7 mg kg⁻¹), Fe (34–63 mg kg⁻¹), Mg (358–588 mg kg⁻¹), Mn (3.0–5.7 mg kg⁻¹), Mo (0.34–0.87 mg kg⁻¹), Zn (6.8–11 mg kg⁻¹), As (0.07–0.337 mg kg⁻¹), Cd (0.017–0.04 mg kg⁻¹), Pb (0.004–0.017 mg kg⁻¹) and Se (0.16–0.489 mg kg⁻¹). Results obtained by direct analysis of miswak by ETV-ICPOES are in agreement with those obtained by ICPOES following conventional acid digestion. The analysis of thin (0.5 cm diameter) and thick (1 cm diameter) miswak revealed significantly higher concentrations of As, Cd, Fe, Mg, Mn, Mo, Pb, and Se in thick miswak than in thin miswak, indicating accumulation of these elements over time as miswak grows. Peeling off the surface layer of miswak revealed the adsorption or deposition of Fe and Mn, and removed a significant portion of potentially toxic elements, such as Pb and Se.