Development and optimization of simplified method of fast sequential HR-CS-FAAS analysis of apple juices on the content of Ca, Fe, K, Mg, Mn and Na with the aid of response surface methodology.

A new method for fast sequential measurements of concentrations of Ca, Fe, K, Mg, Mn and Na in apple juices by high resolution-continuum source-flame atomic absorption spectrometry (HR-CS-FAAS) was developed using response surface methodology (RSM). By combination of Box-Behnken response surface design and desirability functions, compromise conditions of simplified sample preparation of apple juices, including 2-fold dilution with water and acidification with HNO3 to 0.8 mol L-1, were established and verified that provided reliable results. The method was applied for analysis of 20 different samples of commercially sold apple juices. Precision (as relative standard deviation for 3 parallel samples, RSD) and accuracy (as relative error in relation to reference values obtained with prior wet digestion of samples) were very good, i.e. from 0.5% to 6% and from -5 to + 6%, respectively.