Determinação dos teores de cromo e manganês nas frações bioacessíveis de suplementos alimentares

Abstract

This study describes methods for the determination of two minerals, chromium and manganese, in the bioaccessible fractions of food supplements, like hypercaloric, whey protein and protein bars, by graphite furnace atomic absorption spectrometry. For the development of the methods, the bioaccessible fractions were submitted to digestion assisted by microwave radiation and posterior instrumental optimization of pyrolysis and atomization temperatures. For manganese, whey protein and protein bars samples obtained the same pyrolysis and atomization temperatures: 1100 and 1600 °C, respectively; for hypercaloric, the use of the modifier Mg(NO3)2 was employed and the pyrolysis and atomization temperatures were 1200 and 1700 °C, respectively. For chromium, it was not necessary the modifier and the pyrolysis and atomization temperatures for the three types of samples were 1500 and 2300 °C, respectively. The accuracy of the methods were investigated through addition and recovery tests; for manganese the study showed reveries in a range of 84 to 113% and for chromium in a range of 101 to 116%. The precision of the methods was also evaluated and presented relative standard deviation values smaller than 15%. The characteristic mass (mo), limits of detection (LD) and quantification (LQ) for chromium were 1,9 pg, 0,07 i_tg g-1 and 0,2 i_tg g-1, respectively; for manganese, in hypercaloric the values found were 1,8 pg, 0,03 and 0,08 i_tg g-1; and finally, in whey protein and protein bars the values were 4,2 pg, 0,12 ilg g-1 and 0,3 ilg g-1. The developed methods were applied to 12 food supplement samples, being 4 of hypercaloric, 3 of whey protein and 5 of protein bars. Four of those samples presented chromium bioaccessible percentage: 49 and 39% in hypercaloric, 12% in whey protein and 16% in protein bars. On the other hand, only one sample of whey protein did not present significant manganese bioaccessible percentage, varying in a range of 6 to 99%.