Development of procedure for sample preparation of cashew nuts using mixture design and evaluation of nutrient profiles by Kohonen neural network

•Use mixing design to optimize variables involved in the sample preparation process.•Use of microwave-assisted digestion for treatment of the cashew nuts samples.•Establish a procedure for determination of elements in cashew nut using ICP OES.•Apply Kohonen ANN to compare samples from the different states of Brazil. A procedure using ICP OES for sample preparation for the determination of copper, iron and manganese in cashew nuts was developed. Constrained simplex-centroid design was applied in the optimization of the digestion in microwave oven procedure, and the results evaluated from topological maps of the Kohonen network. The best proportion evaluated for the digestion of the sample with HNO3, H2O2 and H2O was 10:45:45 (%). With optimized conditions, the detection limits were 0.63, 4.3 and 0.37 mg kg−1, and quantification 2.1, 14 and 1.2 mg kg−1 for Cu, Fe and Mg, respectively. The precision (% RSD) was 1.84, 2.31 and 2.73, for Cu, Fe and Mg, respectively. The procedure proposed had the accuracy confirmed using NIST 1568b (at 95% reliability) and was applied in the samples obtaining concentrations in the range of 10.7–19.4, 44.3–67.2 and 11.0–21.4 mg kg−1 for Cu, Fe and Mg, respectively.