Direct Analysis of Dark Honeys for Total Content of Copper and Its Fractionation Forms

Abstract

Suitability of direct analysis of honey solutions by air–acetylene flame atomic absorption spectrometry for reliable measuring total concentrations of Cu was evaluated and compared with determinations completed after open vessel wet oxidative digestion of honeys with a mixture of HNO3 and H2O2. Total Cu concentrations determined in amber to dark color raw honeys were within 0.95–1.68 mg kg−1. Additionally, solutions of honeys were subjected to fractionation analysis by means of a two-column solid phase extraction procedure with a non-ionic adsorbing resin Amberlite XAD-16 and a strongly acidic cation exchanger Dowex 50W × 8-200. Another set of solutions was subjected to fractionation analysis using ultrafiltration with membranes of molecular weight cut-off size of 100, 50, 30, 10, and 5 kDa. Both approaches used to partition Cu species enabled to obtain information on chemical and physical fractionation patterns. It seems that predominant classes of species (67–94%) are cationic and residual species which could be the most accessible forms of Cu from honey due to very low molecular size and possible association with certain organic compounds.