A scheme is presented for fractionation of olive components and magnesium determinations in different fractions. The charge of metal species was established using cation exchange with Dowex 50Wx8-40. The resin Amberlite XAD-4 was used for the separation of olive polyphenols in complexes with olive proteins and polysaccharides. The organic and inorganic fraction of magnesium was studied with different solvents as to its bioavailability properties. Flame and electrothermal atomic absorption spectrometry were used off-line for the determinations of magnesium in the different fractions obtained. (C) 2003 Elsevier B.V. All rights reserved.