Multivariate optimization of simple procedure for determination of Fe and Mg in cassava starch employing slurry sampling and FAAS

A slurry sampling procedure has been developed for Fe and Mg determination in cassava starch using flame atomic absorption spectrometry. The optimization step was performed using a univariate methodology for 200mg samples and a multivariate methodology, using the Box-Behnken design, for other variables, such as solvent (HNO₃:HCl), final concentration (1.7molL^-1) and time (26min). This procedure allowed determination of iron and magnesium with detection limits of 1.01 and 3.36mgkg^-1, respectively. Precision, expressed as relative standard deviation (%RSD), was of 5.8 and 4.1% (n=10) for Fe (17.8mgkg^-1) and Mg (64.5mgkg^-1), respectively. Accuracy was confirmed by analysis of a standard reference material for wheat flour (NIST 1567a), which had certified concentrations of 14.1±0.5mgkg^-1 for Fe and 40±2.0mgkg^-1 for Mg, and the concentrations found using proposed method were 13.7±0.3mgkg^-1 for Fe and 40.8±1.5mgkg^-1 for Mg. Comparison with concentrations obtained using closed vessel microwave digestion was also realized. The concentrations obtained varied between 7.85 and 17.8mgkg^-1 for Fe and 23.7-64.5mgkg^-1, for Mg. The simplicity, easily, speed and satisfactory analytical characteristics indicate that the proposed analytical procedure is a good alternative for the determination of Fe and Mg in cassava starch samples.