Elemental Analysis of Dietary Supplements by Microwave-Induced Plasma–Optical Emission Spectrometry (MIP-OES) With Ultrasound-Assisted Extraction (UAE)

The purpose of this study was to demonstrate the feasibility of determining metals (Cr, Mn, Zn, Fe, and Cu) in commercial dietary supplements using microwave-induced plasma optical emission spectrometry (MIP OES) after fast ultrasound-assisted extraction. Various parameters affecting the extraction process, such as the nature and concentration of the extractant solution, sonication time, and sample mass, were evaluated. Under the optimal conditions, it was possible to quantitatively extract metals from the samples by sonicating 1.0 g of the supplement dispersed throughout 25 mL of a 1.0 mol L−1 HNO3 for only 5 min. The developed method was applied to determine the analytes in four dietary supplements available in the Brazilian market. The results obtained with the extraction method were compared with the values obtained when the samples were completely mineralized with concentrated HNO3 in a microwave oven. There were no statistical differences between the developed and reference methods when the paired Student's t-test was applied with a 95% confidence level. The application of ultrasound-assisted extraction was demonstrated to be advantageous compared to total sample digestion. This approach allowed the use of a higher mass of the sample, thereby enhancing the analytical capability of the method. Furthermore, employing less severe conditions, such as lower energy and a diluted acid solution, simplified and reduced the cost of the procedure compared to mineralization.