A revisited FAAS method for very simple and fast determination of total concentrations of Cu, Fe, Mn and Zn in grape juices with sample preparation developed by modeling experimental design and optimization

A method for determining total concentrations of Cu, Fe, Mn and Zn in red and purple grape juices by flame atomic absorption spectrometry (FAAS) combined with simple sample preparation by dilution of samples with HNO3 solutions was revisited. A design of experiment (DOE) approach was used to establish optimal conditions of the mentioned dilution/acidification sample preparation procedure. It was found that 4-fold dilution of original samples with a HNO3 solution so as to reach its final concentration of 0.85 mol L-1 provided precise (related standard deviations from 1% to 9%) and true (relative errors from - 5% to + 4%). Limits of detection of studied elements were within 0.01 to 0.04 mu g mL(-1). Once optimized, the newly developed method was applied for very simple and fast analysis of nine commercially available grape juices, avoiding possible losses of analytes and reducing any risk of contamination of samples.