Estudo da potencialidade da radiação infravermelha no preparo de amostras de linhaça e camarão para análise de traços por FAAS E ICP OES

Abstract

The sample preparation is a critical step of the analytical sequence, so the development of faster, more efficient and cheaper sample preparation methods is important. Sample preparation systems that use infrared radiation as a source of heating have been shown as a good alternative to achieve such objectives. The extraction of Cu, Fe, Mn and Zn in flax samples and As, Cd, Co, Cu, Fe, Mn, Ni, Se and V in shrimp samples for subsequent quantification of these elements using FAAS and ICP OES, respectively, was studied. Full factorial planning at two levels and desirability function were applied to evaluate the best extraction condition of the analytes from the samples studied. For flaxseed sample, the experimental conditions were: 2.0 g sample mass, 8 mL HNO3, and 8 min of heating time at 500 W infrared (IR) lamp power. For shrimp sample preparation: 1.0 g of sample mass, 8 mL of HNO3, 8 min of heating time at 500 W of IR lamp power. In these conditions, results with good accuracy and precision <10% RSD for flaxseed and <17% RSD for shrimp were obtained. The accuracy of the methods was verified by analysis of rice bran and oyster tissue certified reference materials. The efficiency of IR extraction system was evaluated by %RCC obtained to certified reference material (oyster tissue) analysis in comparison with those when was used digester block. Both sample preparation methods showed similar % RCC values. Standard samples of glycine, phenylalanine and nicotinic acid were also submitted to IR system and digestor block, and, both systems presented similar % RCC values for glycine. However, the inverse behavior was obtained for phenylalanine and nicotinic acid. It was also observed the positive effect of the presence of glucose on digestion of these compounds, reducing the %RCC for all of them. The IR-assisted sample preparation system provides a quick and inexpensive alternative to other conventional techniques for the analysis of trace elements in samples of food of plant and animal origin. It had the capacity to accommodate relatively large sample masses, avoiding homogeneity problems, as well as increasing the detection power.