Determination of Major, Minor, and Toxic Elements in Tropical Fruits by ICP-OES After Different Microwave Acid Digestion Methods

Abstract

Fruits contain nutrients, minerals, trace elements, vitamins, and phytochemicals that are important in terms of human health. When fruits are consumed in a balanced diet, they have a positive effect with regard to reducing disease risk. As a result of heavy metal contamination of the environment, they can be a potential source of toxic elements so it is important to determine the toxic, essential, and trace elements in fresh fruit and commercial fruit products such as fruit juice, marmalade. This study aims to determine the concentrations of Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, Zn, P, and S in tropical fruits (tamarind (Tamarindus indica), star fruit (Averrhoa carambola), golden berry (Physalis peruviana), kumquat (Citrus japonica), dragon fruit (Hylocereus undatus), passion fruit (Passiflora edulis)) by using inductively coupled plasma optical emission spectrometry (ICP-OES) after different microwave acid digestion procedures. The efficiencies of digestion in tropical fruit samples were investigated and compared. Six milliliters of HNO3 + 2 mL of H2O2, 6 mL of HNO3 + 2 mL of HCl, 8 mL of HNO3, 8 mL of HNO3 + 4 mL of H2O2(30%), 8 mL of HNO3 + 4 mL of HCl, and 12 mL of HNO(3)were used for microwave acid digestion procedures. Microwave digestion procedures were applied for the analysis of seventy-two tropical fruit samples purchased in triplicate for each tropical fruit and major, toxic, and minor element contents of tropical fruits were determined. The parameters of the merit evaluated were validated according to limits of detection (LOD) and limits of quantification (LOQ), linearity, recovery, and precision. The highest results of LOD and LOQ were found for Ca, K, Na, Mg, and S. The recovery percentages are in the range from 71.01 to 117.31% in tropical fruits. The digestion efficiency was correlated with the residual carbon content, which was determined by total organic carbon analyzer (TOC). Six milliliters of HNO3 + 2 mL of HCl digestion method was chosen as the effective digestion method because of the lowest residual carbon contents and the accuracy results.