Desenvolvimento de metodologia analítica para determinação da arroz por concentração total e fração bioacessível de metais em Espectrometria de Emissão Desenvolvimento de metodologia analítica para determinação da concentração total e fração bioacessível de metais em arroz Espectrometria de Emissão Óptica com Plasma Induzido por (MIP OES)

Abstract

This work presents the studies related to the development of analytical methods for determination of total concentration and bioacessible fraction of metals such as Al, Ca, Cu, Fe, Mg, Mn, Na, K, Si and Zn in rice using the Microwave Induced Plasma Optical Emission Spectrometry. Samples of brown, white and parboiled rice were analyzed, in raw and cooked form. The optimal conditions for sample preparation using acid decomposition with reflux system were: mass sample (1.5 g); concentrated HNO3 (5.0 mL); H2O2 (1.0 mL), temperature of digester block (150 °C) and total decomposition time (4 hours).The accuracy was ensured through analysis of certified reference material of rice and analyte addition tests, with recoveries ranged between 80 and 120%.To determine the bioaccessible concentration of the elements, a simulation of the gastrointestinal system was performed, in which the accuracy was proven through the sum of the bioaccessible fraction and the non-bioaccessible fraction, which must be close to the results of the total concentration, with the recoveries obtained in the range from 50 to 120%.The limits of detection and quantification obtained showed to be adequate for the quantification of metals in different types of rice according to Brazilian legislation. All concentration values found in the investigated rice samples showed relative standard deviation values less than 13.8%, confirming good accuracy. According to the results obtained from the total concentration, it was observed that there is a variation in concentration when comparing the values of each type of rice between raw and cooked, and for the analytes Ca, K and Mg higher concentrations were observed. Regarding to the bioaccessibility study, the fractions found for the raw rice samples ranged between 3.0 to 81.0% for Fe; 1.9 to 60.0% for Mn and 9.0 to 80% for Si. For the cooked rice samples, the bioaccessible fractions ranged from 7.0 to 40.2% for Fe; 1.0 to 86.1% for Mn and 4.0 to 73.6% for Si. In relation the recommended daily intake, only Mg and Mn exceeded the maximum limit recommended in some samples. For the bioaccessible fraction, none of the elements exceeded the recommended daily intake. Thus, it becomes necessary to eat other food sources, since only rice is not able to supply the nutritional quantities necessary for a balanced diet.