Desenvolvimento de método analítico para determinação de Mn, Zn, Cu e Fe em amostras de arroz por Espectrometria de Absorção Atômica com Chama

Abstract

The development of new analytical methodologies have been studied for the determination of metals in rice, these methods involving more practicality, with a relatively lower cost than existing conventional sample preparation. In this work, we developed a method of sample preparation for determination of metals by atomic absorption spectrometry with flame (FAAS), aiming at the quantification of Mn, Zn, Cu and Fe through the use of a cold finger as aid in digestion the samples. Values were obtained from the sample detection limit (LD), in mg kg-1 of 2.12, 0.16, 0.36 and 1.84 for Mn, Zn, Cu and Fe respectively. The instrumental limits of quantification (LOQ) were 0.179, 0.015, 0.030 and 0.150 in mg L -1 for Mn, Zn, Cu and Fe respectively. The accuracy of the proposed method for the determination of these metals was verified by comparing the results with two other methods of sample preparation (conventional methods 1 and 2), and was also checked by using Certified Reference Material NIST 1568a CRM flour rice and a control sample of rice husk from a laboratory plant in São Paulo. By comparing the results obtained for Mn, Zn, Cu and Fe between the cold finger of the proposed method and the conventional methods 1 and 2, it was found that these were not significantly different at a level of 95% with the application of the paired Student t-test. For the results of the control sample and the reference material were found in concentrations that averaged 95% agreement with the certified values, except for the element Fe to the control sample. The methodology proposed is efficient cold finger, because the values for relative standard deviation (RSD) for the different rice samples showed good reproducibility between measurements (RSD <10%). Compared with conventional methods 1 and 2, the RSDs were better for most rice samples, highlighting the elements Fe and Cu showed that lower values of RSDs, showing that the proposed method achieved better accuracy in analysis. With this, the proposed method has proved to be simple, with little amount of reagent because only the HNO3 was used for digestion of the sample, proving to be a suitable method for preparing the samples.