Fractionation of calcium and magnesium in honeys, juices and tea infusions by ion exchange and flame atomic absorption spectrometry

An analytical procedure was proposed to study the operational fractionation of Ca and Mg in bee honeys, fruit juices and tea infusions. The protocol devised was based on the solid phase extraction of distinct metal fractions on different sorbents, namely strong acidic cation exchanger Dowex 50Wx4, weak acidic cation exchanger Diaion WT01S and strong basic anion exchange resin Dowex 1x4. For the evaluation of the amounts of the metal fractions distinguished, a flame atomic absorption spectrometry was used off-line prior to the determination of Ca and Mg concentrations in the effluents obtained. It was established that Ca and Mg are mostly present in the analysed samples in the form of cationic species (96–100%). The accuracy of the entire fractionation scheme and sample preparation procedures involved was verified by the performance of the recovery tests.