ABSTRACT
Objective
In this paper, we studied three different types of ordinary sports supplements containing whey protein: whey protein-based ones, hypercaloric ones, and protein bars.
Methods
A sample preparation procedure was studied employing microwave-assisted wet digestion in order to determine the Chromium and Manganese levels by graphite furnace atomic absorption spectrometry.
Results
The developed methods have presented good accuracy (recoveries in the range of 90% to 109%) and precision (Relative standard deviation <8%). Although an adequate detectability was obtained (50ng g-1 for Manganese and 65ng g-1 for Chromium), the sample preparation method was also adequate to inductively coupled plasma mass spectrometry analysis. The method was applied to 26 commercial samples, in which the Chromium concentrations were in the range between 0.22 and 1.0μg g-1 and the Manganese concentrations varied from 2.0 to 37μg g-1.
Conclusion
The results obtained by atomic absorption for both analytes were in agreement with those obtained by mass spectrometry. In addition, some samples presented concentrations of Chromium above the recommended daily intake and, as a result, we used the X-ray powder diffraction technique as an analytical tool to evaluate the oxidation state of Chromium in such samples.
Keywords
Atomic absorption; Chromium; Manganese; Micronutrients; Supplements; X-ray diffraction
Note: The chemical modifier used to Chromium determination was 12.75μg of Mg(NO3)2. Response surface analysis of variance: (A) Ffaj=0.67, Freg=36.5; (B) Ffaj=0.68, Freg=92.6; and, (C) Ffaj=0.66, Freg=121.4. Ffaj-crit=19.2 and Freg-crit=5.05. Ffaj: Lack-of-fit F-test. Freg: Regression F-test. Ffaj-crit: Lack-of-fit F-test critical. Freg: Regression F-test critical.
Note: Reading: Black: Chromium (III) Picolinate; Red: Chromium Trioxide; Pink: Whey Protein sample 7; Blue: Supplements of the Hypercaloric Type, sample 2; Green: Supplements of the Hypercaloric Type, sample 1.