Analysis of Essential and Nonessential Elements in Local and Imported Raw and Cooked Rice (Oryza sativa) Samples in...

This study aimed to measure the concentrations of essential and nonessential metals in raw and cooked rice samples from Ethiopia. Researchers collected rice samples, both local and imported, from the Jimma town market. The samples were stored in prerinsed plastic bags and rinsed with 2 mol/L HNO₃ and deionized water to prevent contamination. Preparation involved wet digestion methods, and the samples were stored at 4°C until analysis. Flame atomic absorption spectrometry (FAAS) was used to analyze the samples in triplicate, and the results were validated for accuracy, precision, instrument detection limit (IDL), limit of detection (LOD), and limit of quantification (LOQ). The findings revealed significant differences (p < 0.05) in the mean concentrations of metals across all rice samples. The metals detected included both essential and nonessential types: chromium (Cr) ranged from nondetectable (ND) to 15.36 mg/kg; nickel (Ni) from ND to 17.76 mg/kg; cadmium (Cd) from 1.22 to 5.58 mg/kg; lead (Pb) from 0.17 to 0.98 mg/kg; iron (Fe) from 19.99 to 84.71 mg/kg; calcium (Ca) from 35.15 to 198.53 mg/kg; potassium (K) from 35.31 to 105.19 mg/kg; and magnesium (Mg) from 18.66 to 46.07 mg/kg. The percentage recoveries ranged from 80.5% to 120%, indicating good accuracy and repeatability of the analytical procedure. The study also found significant variations among the six metals, suggesting that geographic origin influences metal levels in rice. Notably, while there was no significant difference between cadmium and calcium concentrations, the levels of nonessential metals, cadmium, lead, and nickel, exceeded the recommended limits set by WHO/FAO. Based on these findings, the study recommends careful handling of rice during transportation, marketing, storage, and cultivation to minimize exposure to toxic metals.