Determinação de Na, K em amostras biológicas e Hg em álcool combustível por Espectrometria Atômica

Abstract

In Chapter 1, a new procedure based on solubilization of the processed meats samples using tetramethylammonium hydroxide (TMAH) was developed for the determination of Na and K by flame atomic emission spectrometry (F AES). The proposed methodology was validated through tests of addition and recovery of analyte, as well as using different decomposition procedures in the presence of nitric acid or formic acid after application statist test, which showed no significant differences between the results compared with a confidence level of 95% with application test t of Student. Limit of detection (LOD) 0.8 μg g-1 for Na and 2.0 μg g-1 for K were obtained using TMAH. The proposed methodology is very simple, requiring small amounts of sample and reagent, proving to be efficient in solubilization of the analyzed samples for later determination of the respective elements. The potential for application to other sample types and analytes is evident. In Chapter 2, a new procedure based on the exposure of fuel ethanol samples to UV radiation in the presence of organic acids of low molecular weight was developed for determination of total Hg from inorganic and organic species (Hg2 +, CH3Hg+ and CH3CH2Hg+) by photochemical vapor generation coupled with atomic absorption spectrometry (photo - CV-AAS) using different kinds of systems for vapor generation. For each species, the optimum conditions for the photochemical generation were investigated such as the effects of concentrations in medium of sample preparation, time of exposure to UV radiation from the sample and carrier gas flow rate. The accuracy was evaluated through tests of addition and recovery of analyte individually and in a mixture of all species of the metal in fuel ethanol samples, using calibration standards in media with bidestilled alcohol. The recovery results were satisfactory (91-107%) for different species of analyte in both medium of sample XV preparation, either in the commercial system (1) as in the adapted system (2). Limits of detection were obtained in a range from 0.10 to 0.20 μg L-1 for the commercial system and from 0.06 to 0.09 μg L-1 for the adapted system for all addition and recovery tests, enabling the determination of total Hg. The proposed methodology is sensitive, simple and inexpensive, and promotes the “green” chemistry. The potential for application to other sample types and analytes is evident.