Solid phase extraction and sequential elution for pre-concentration of traces of Mn and Zn in analysis of honey by flame atomic absorption spectrometry

Abstract

A pre-concentration procedure based on solid phase extraction and two-step elution was developed for the determination of the total concentrations of traces of food safety relevant elements (Mn and Zn) in ripened honeys. Accordingly, 10% (m/v) solutions of analyzed honeys (100 ml) were passed at 20 ml min⁻¹ through resin beds of Dowex 50W × 8–400 to retain Mn and Zn ions and separate them from the glucose and fructose matrix. Afterwards, 20 ml of a 0.5 mol l⁻¹HNO₃ solution was used to elute K and Na, easily ionized interfering metals. Finally, Mn and Zn were recovered prior to measurements by flame atomic absorption spectrometry (FAAS) using 5 ml of a 2 mol l⁻¹HCl solution. This procedure was applied in the analysis of six honeys and resulted in the determination of 0.2–13.6 μg g⁻¹ of Mn and 0.2–1.2 μg g⁻¹ of Zn with the precision (n = 3) within 3–10% and an accuracy better than 5%. Detection limits of Mn and Zn with this pre-concentration/separation procedure and the FAAS detection were 4 and 3 ng g⁻¹, respectively.