DETERMINATION OF TOTAL ARSENIC AND ARSENIC SPECIATION IN DIFFERENT PROCESSED RICE SAMPLES (WHITE, PARBOILED AND BROWN) FROM DIFFERENT BRAZILIAN REGIONS

Rice is a dominant staple food for over half of the world’s population, especially in Brazil, since it is an important component of basic Brazilian diet, with an average ingestion of about 160.3 grams a day. This cereal is able to supply 20% of an adult’s daily energy and 15% of an adult’s daily protein needs. In addition, it contains vitamins, minerals, phosphorus, calcium and iron. However, it is important to realize that rice may have contain toxic elements, such as arsenic (As)1. Arsenic is a well-known toxic element, which has been highly regulated, although regulatory limits have been established only for total arsenic, while its toxicity is widely dependent on its chemical form2. The most toxic forms of arsenic are its inorganic species, such as As3+ and As+5, while organic species, such as monomethylarsonic, dimethylarsinic, and arsenobetaine, are less toxic. The aim of this study was to investigate total arsenic and As speciation in different processed rice samples (white, parboiled and brown) from different Brazilians regions. Total arsenic was quantified by ICP-MS, NexION® 300D model (Perkin Elmer), and by GF AAS, PinAAcle 900Z model (Perkin Elmer). For the different forms of arsenic an HPLC/ICP-MS coupling was used. The HPLC, model FlexarTM, separates the forms and the ICP-MS detects them as they elute from the column. Two-hundred and seventeen samples, from different rice subgroups and brands, were sampled from supermarkets in different regions of the country: 33 from the northern region; 57 from the southeast region; 45 from the central-west region and 82 samples from the southern region, the largest rice-producing region of the country, contributing with 90% of the total rice production. Total arsenic means, considering all the analyzed samples, was of 0.105 mg kg -1 with the median of 0.1 mg.Kg -1 and the 90th percentile of 0.187 mg.Kg -1.Only 10% of the analyzed samples presented results between 0.2 mg.Kg -1-0,3 mg.Kg -1, the maximum permissible limit by Brazilian norms, and were subsequently evaluated regarding As. The mean percentages found for the determined As species were of 39% for As3+ (0.07-0.11 mg.Kg -1), 20 % for As5+ (0.03-0,05 mg.Kg-1) and 40% for organic arsenic (0.07-0.12mg.Kg -1). Although arsenic concentrations in all samples was lower than the established limit by the legislation (0.3 mg.Kg -1) the importance of monitoring As rice contamination is clear due to this elements’ high toxicity and the risk that it represents.