Analysis of arsenic in raw and cooked rice by atomic absorption spectrophotometer

Abstract

Arsenic is a highly toxic and carcinogenic metalloid. Rice is a staple food that is widely used in the world, especially in Indonesia. Several studies have shown that arsenic level in rice is influenced by the environment and genetic differences of rice. The process of cooking in raw rice may reduce arsenic level in rice. The purpose of this research was to study the effect of cooking process using demineralized water and tap water on arsenic contents in rice. The samples used were white rice (Oryza sativa L), brown rice (Oryza rufipogon), "brown" rice (Oryza punctata) and black sticky rice (Oryza sativa var glutinosa) obtained from several traditional markets in Medan. The process of cooking was done using two types of water, namely demineralized (reverse osmosis; RO) water and tap water. The determination of arsenic level was carried out using atomic absorption spectrophotometer with argon-air flame at wavelength of 193.7 nm. The results showed that the highest arsenic content of 0.3061 mg/kg was found in red rice and the lowest arsenic level of 0.0693 mg/kg was found in white rice. Process of cooking with RO water and tap water reduced arsenic level in cooked rice. The highest reduction in arsenic content (21.93%) caused by cooking process using RO water and 11.40% caused by cooking with tap water. The result showed that the arsenic safety index in raw rice and cooked rice, based on the daily intake according to the excess cancer risk, exceeded the WHO safety standard.