Abstract
This study reports the microwave-assisted preparation of sports supplements using dilute nitric acid followed by the determination of Ca, K, Mg, Na, P and S using inductively coupled plasma–optical emission spectrometry (ICP-OES). Microwave-assisted digestion was optimized using modified Doehlert experimental design based on the overall desirability of residual acidity, dissolved organic carbon and recoveries obtained for a diet-certified reference material using the nitric acid concentration and volume of hydrogen peroxide. The digestion was performed using 2 M HNO3 and 1 mL 30% H2O2. The accuracy and precision were evaluated by recovery tests, and satisfactory recoveries ranging from 91% to 110% were obtained by ICP-OES. Nine sports supplements were analyzed with concentrations from 3351 to 7069 mg kg−1 for Ca, 3870 to 13,639 mg kg−1 for K, 626 to 2678 mg kg−1 for Mg, 1293 to 5170 mg kg−1 for Na, 2888 to 7845 mg kg−1 for P and 3217 to 10,965 mg kg−1 for S. Qualitative analysis by gel electrophoresis characterized the similarities and differences between the supplement protein profiles. In addition, a comparison of the correlations between the analytes and the supplement formulations was performed by a correlation graph and principal component analysis (PCA).
Acknowledgment
Instrumental support provided by Analítica and Thermo Scientific is gratefully acknowledged.