Determinação de sulfaguanidina sódica empregando sistema FIA. Préconcentração e determinação de organofosforados utilizando material de acesso restrito

Abstract

This thesis describes the evolution of two analytic methods: I- Systems of flow injection analysis for determining the sodium sulfaguanidine in pharmaceutic and food samples and II - The determination of organophosphates' pesticides, in food samples, using magnetic material of restrict access for pre concentration. In the first analysis, the method based itself on the reaction of sulfaguanidine with nitric ion and n-naphthylethylenediamine to produce a colored complex, which the absorbance was monitored in 545 nm. The system was optimized, using a fractional factorial planning 2 7-2 and Doehlert matrix. The method was aplyed in samples of medicines and food (egg, milk and chicken's liver). The possible interfering were evaluated by multivariated technique and represented in probabbiliry's graphics, and there were no significant interferences in a reliable level of 95%. The method showed us limits in detecting and quantifing in 0.012 mg. L-1 and 0.039 mg. L- 1, respectively, nalytic frequency of 30 readings.h-1 and good accuracy demostrated by relative standard deviation under 4.0%. The results agreed to the results obtained by the technique of high-performance liquid chromatography, testing the method's accurancy. In the second analysis, it was synthesized a magnetic material of restrict access (M-RACNT), to extract the organophosphates' pesticides of food samples with high protein level. The material's magnatization auxiliates the division in dispersive phase, as the carbon nanotubes are hard to devide in water environment. Thus, with the help of a magnet, it was possible to separate the sample's sorbent material. On the other hand, the serum albumin which covers the carbon nanotubes constitutes a physical barrier, stopping the proteins to absorve the material. However, the organophosphates, for being smaller molecules, can migrate and be absorbed by M-RACNTs, ensuring the extraction of the matrix. The material resulted was capable of excluding about 100% of the proteins in the environment, this test was ensured by experiments of protein removal. Later to the proccess in solid stage, the samples were checked, using a system of flow injection analysis with spectrophotometric (560 nm). The system was optimized, using a fractional factorial planning 26-2 and Doehlert matrix. The method was applyed to determine organophosphates' pesticides in five food samples (brocolli, eggplant, cauliflower, soy milk and beans). In relation to the merit, the method presented a linear range between 5 μg L- 1 and 90μg. L- 1, limit of detection of 0,74 μg. L-1, limit of quantification of 2,44 μg L- 1, pre concentration factor 271 times under and RSD inferior to 3.67%. The accurancy of the method was evaluated in comparison to the technique of high-performance liquid chromatography. The results were consistent (test-t, p = 0,05).