Chemical sample preparation of plant materials in tunnel-type microwave digestion systems for elemental analysis

Analyzing plant materials is essential for environmental monitoring, analytical control of food products, and medicinal raw materials. A review of global practices has shown that there are still no standard proceedings for chemical sample preparation suitable for all plant types without restrictions on the range of elements determined. Creating a standardized scheme for plants is feasible, as the macro composition of any plants consists of at least 90% organic compounds (cellulose, protein, lipids, etc.), whose mineralization results in the formation of water and a gaseous phase. In this study, certified plant samples were mineralized in a tunnel-type microwave digestion system MultiVIEW (SPC SCIENCE, Canada) with variations in analytical sample sizes, composition and volume of reagents, options for adding the reaction mixture, and vessel heating modes for simultaneous determination of a wide range of elements using inductively coupled plasma atomic emission spectrometry. The completeness of dissolution (the degree of correspondence between found and certified contents) was used as one of the criteria for the optimality of sample preparation conditions. It was shown that with a three-stage heating regime of the vessels (heating rate at the first stage 2.76 оC/min) with a sample weight of 0.5 g and separate sequential addition of the reaction mixture (4 ml HNO3, 1.5 ml H2O2, 1 ml HCl, and 0.05 ml HF), it is possible to reliably determine typical plant contents of Si, Al, Mg, Ca, Fe, Na, K, Ba, Sr, Rb, P, B, Mn, Ti, Ni, V, Cu, Zn.