Evaluation of Trace Element Concentrations in Food Supplement SamplesUsing Different Digestion Methods by ICP-OES

Introduction: Dietary supplements are widely consumed under the assumption that they pose no harm to human health. However, these supplements may contain trace and toxic elements that can exceed the recommended daily intake levels, potentially endangering health. Therefore, assessing the levels of metals in dietary supplements is crucial to ensure their safety. This study aimed to determine the concentrations of B, Cu, Fe, Mn, Zn, P, Al, Na, Mg, K, and Ca in food supplements, including bromelain tablets and capsules, melatonin tablets and capsules, collagen tablets and powder, saw palmetto tablets and capsules, spirulina powder and tablets, and probiotic sachets. This research utilized various digestion methods for the first time in food supplement samples, analyzed by İnductively Coupled Plasma Optical Emission Spectrometry (ICP-OES). Methods: To compare the efficiencies of digestion in food supplement samples, the following reagents were employed: 7 mL of HNO3 (65%) and 3 mL of H2O2 (30%) for the microwave digestion method, and 7 mL of HNO3 (65%) and 3 mL of HCl (37%) for another microwave digestion method. Additionally, 7 mL of HNO3 (65%) and 3 mL of H2O2 (30%) were used for the wet digestion method. Results: The recovery percentages ranged from 78.88% to 106.60% in food supplement samples. The highest LOD and LOQ results were observed for K, Ca, Na, and P, while the lowest results were noted for Cu, Mn, Mg, and Zn. The concentrations of B, Cu, Fe, Mn, Zn, P, Al, Na, Mg, K, and Ca in food supplements (minimum–maximum in μg/g) were as follows: 1.55-16.59, 0.49-50.68, 1.35-447.40, 0.39-82.29, 2.68-4677.10, 3.45-8233.5, 6.59-138.7, 49.30-15033.50, 1.69-1699.3, 3.25-13496, and 21.33-2435.42 μg/g, respectively. Discussion: The parameters of Limits of Detection (LOD), Limits of Quantification (LOQ), recovery, linearity, and precision were evaluated for validation purposes. The efficiencies of digestion in food supplement samples were compared. Conclusion: The HNO3/H2O2(7:3) microwave digestion method was chosen as the most appropriate digestion method because the highest element concentrations and recoveries for many elements were observed. The concentrations of the analyzed elements (except for Al in collagen tablets) are within the permissible limits set by international authorities.