Rice is one of the most highly demanded crops worldwide as it is one of the bases of human nutrition but since plants take nutrients from the soil, in recent decades several studies have established that additional to the uptake of the usual elements (C, N, P etc.). This also occurred with some trace and toxic elements which then accumulated in the plant, including the grains that are consumed by humans. Accurate determination of trace elements in rice is therefore very important for preserving the high nutritional value. Furthermore, the analysis of trace elements plays an important role as a basis for rice provenance and quality control, as has been studied previously in other food matrices. The most common methodologies reported for rice sample treatment tend to use concentrated reagents and longer digestion times. However, the implementation of diluted acid could led to a more environmentally friendly approach to determine elements in rice grains. This study aims to develop a method that follows then green chemistry guidelines to improve the sample digestion of rice for analysis by inductively coupled mass spectrometry (ICP-MS), that also achieves accurate and reproducible results with low detection limits for some elements. The method was designed to carry out the sample preparation and instrumental analysis from a single tube to prevent sample loss, minimize contamination, reduce digestion times, volumes of acid and the required final dilution. To evaluate the best and fastest sample preparation procedure, wet digestion methods were compared using rice certified reference material (NIST 1568b Rice Flour) with different reagent mixtures, reagent volumes, and times for sample digestion. Using a mixture composed of 1.0 mL of 1% (v/v) HNO3 and 0.5 mL 30% (v/v) H2O2 for sample digestion in a water bath (95 °C, 40 min) was found to produce satisfactory results for Ca, Cd, Cu, K, Mn, Mo, Rb and Zn with concentrations between 80-110% of the certified values. In the future this method could be used as routine analysis with high sample throughput for rice samples and also as a base study that could be extended to other related matters such as health risk assessments, provenance studies, quality of crop growth, and more.
A greener digestion method for the analysis of some elements in rice using ICP-MS / Natalia Puente De La Cruz, Laura; Marconi, Elisabetta; Astolfi, Maria Luisa. - (2022). (Intervento presentato al convegno The First Symposium for YouNg Chemists: Innovation and Sustainability (SYNC2022) tenutosi a Rome, Italy).