Evaluation of Partial Digestion as a Strategy for Elemental Analysis of Inorganic Samples by Inductively Coupled Plasma–Optical Emission Spectrometry (ICP OES)—A Proof of Concept Study

This study discusses the application of microwave-assisted sample preparation for inorganic samples using concentrated or diluted HNO3 solutions followed by determination of Al, Ca, Cu, Cr, Fe, K, Mg, Mn, Na, Ni, P, Pb, S, Si, and Zn using inductively coupled plasma–optical emission spectrometry (ICP OES). Aiming the total digestion (reference procedure), samples were decomposed in a heating block using a mixture of 2 mL of 40% v v−1 HF and 5 mL of 14 mol L−1 HNO3. Four digestion mixtures composed by (1) 14, (2) 7.0, (3) 4.0, and (4) 2.0 mol L−1 HNO3 plus 3 mL of concentrated H2O2 were evaluated as alternatives for microwave-assisted digestion of six inorganic samples (partial digestion). Considering all evaluated procedures, quantitative recoveries were obtained applying reference and partial digestion procedures. Therefore, the use of HNO3 dilute solutions as an alternative for HF is a feasible procedure for quantitative analysis of zinc oxide, kaolin, zinc residue, and zinc sulfide. However, tailored procedures must be taken into consideration, since quantitative determination depends on digestion mixture, sample matrix, and analytes.