Abstract
Dietary supplements may contain heavy metals with the property of bioaccumulation in humans. The aim of this research was to validate and apply two analytical methods to determine Pb, As, Cr, and Hg in dietary supplements by Total Reflection X-ray Fluorescence Spectroscopy (TXRF). Methods validation was conducted through a multivariate analysis using a central composite design (CCD) and a desirability function. Critical values for each study variable were established. The TXRF_DS_1 method was proposed for Pb, As, and Cr determinations, while the TXRF_DS_2 was established for Hg analysis. The digestion method with an acid mixture (HNO3 + HCl + H2O2) was used to break down the organic material of dietary supplements. A solution of 10 μg L−1 Ga was used as an internal standard. Excellent analytical performance was obtained as LODs of 0.59, 0.41, 0.57, and 0.75 μg L−1 and LOQs of 1.95, 1.35, 1.90, and 2.50 μgL −1 for Pb, As, Cr, and Hg, respectively. Calibration curves showed a good linearity for all elements (R2>0.999). Excellent accuracy and precision in measurements (% RSD) was achieved. The real and spiked samples analysis demonstrated the applicability of the TXRF technique (percentage recovery 91–108%). Besides, two samples were analyzed in a comparison study between the TXRF_DS_1 method and the ICP-OES method. The results obtained showed good agreement between both techniques. The TXRF technique allows the analysis of toxic heavy metals in dietary supplements, which are marketed in a wide variety of presentations.
Highlights
Dietary supplements are products that contain a “dietary ingredient” which includes vitamins, minerals, and amino acids, as well as other substances that can be used to supplement the diet [1]. ey can be prepared from decoctions from fresh or dried crude herbs from algae or plants, but are usually made into different presentations, including powders, tablets, capsules, energy bars, and liquids [2]. e consumers believe that since these products contain ingredients that come from plants, they are safe and without any adverse effect [3]
People could be at risk of adverse health effects from consuming dietary supplements made with plants grown in soils containing elevated metal concentrations [4]. (b) Contamination may occur during the production processes
Detection limits for Pb, As, Cr, and Hg were lower than limit of detection (LOD) obtained with an inductively coupled plasma optical emission spectrometry (ICP-OES) method for the quantitative analysis of toxic elements in some dietary supplements and EDTA mol·L−1
Summary
Dietary supplements are products that contain a “dietary ingredient” which includes vitamins, minerals, and amino acids, as well as other substances that can be used to supplement the diet [1]. ey can be prepared from decoctions from fresh or dried crude herbs from algae or plants, but are usually made into different presentations, including powders, tablets, capsules, energy bars, and liquids [2]. e consumers believe that since these products contain ingredients that come from plants, they are safe and without any adverse effect [3]. There were two research purposes, the first being to contribute to the risk assessment analysis regarding the consumption of dietary supplements and the second being to propose the TXRF technique as a powerful tool for quality standardization and control of both raw material and finished product. E present work utilized a digestion procedure using concentrated HNO3 + HCl + H2O2 for the determination of Pb, As, Cr, and Hg in six dietary supplements [2, 24].
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