Quantitative and qualitative studies of silica in different rice samples grown in north of Iran using UV–vis, XRD and IR spectroscopy techniques

Silicon is an essential trace element and is found in vegetables, fruits, cereals, water, pasta and rice (Oryza sativa). In this work, the silica content of different types of rice grains were measured. Here, we used the heteropoly blue photometric method with a double beam UV–vis spectrophotometer to determine the amount of silicon in rice samples (n = 7) that were collected in the north of Iran. The samples were digested with wet-ashing method by microwave-assisted heating and then treated with ammonium molybdate to produce a yellow color compound in acidic solution (ca. pH 1.2) and then reduced to give a heteropoly compound with a blue color. Analyses were performed using standard addition method and absorbance values were measured with double beam UV–vis spectrophotometer at λmax = 815 nm. Results indicated that the silica content was 307–451 mg/kg for the samples. X-ray diffraction patterns and infra-red spectra were obtained from rice samples without any sample treatment.