DEVELOPMENT OF AUTOMATIC ANALYTICAL METHOD FOR VIAL WALL SORPTIVE EXTRACTION ANALYSIS IN COMPREHENSIVE MULTIDIMENSIONAL GAS CHROMATOGRAPHY

With the great technological advances related to the analysis methods and detectors used to determine the analytes of a complex sample, the use of new sample preparation methods has become increasingly necessary to aid the analytical process. Within the sample preparation process, it is possible to highlight the performance of automated methods, which present lower statistical error compared to traditional ones, in addition to sparing the analyst, avoiding his direct contact with reagents and long periods of work. To assess the credibility of these new methods, ensuring that they will serve the proposed function, an analytical validation is carried out, determining their performance characteristics. This work brings the proposal to automate, optimize and validate a recent method of extraction and pre-concentration, the vial wall sorptive extraction (VWSE), being an efficient, miniaturized and clean method. For the analyzes, it was chosen to work with a multidimensional gas chromatograph, since its use brings the advantages of sensitivity at low concentrations, resolution and level of information obtained. The present work also aimed to develop the best procedure for making VWSE devices and to evaluate the statistical equivalence of the prepared devices, in addition to evaluating the possibility of their use in an automated methodology using a prototype of an automatic sampler available in the laboratory of the Centro Federal de Educação Tecnológica Minas Gerais. In the study, a standard of alkanes of known concentration was used in pure tetrahydrofuran solutions and in a mixture with Mili-Q® water. The VWSE devices were prepared in five different conditions using a lathe and a prototype developed to rotate the vials and spin coat them. The methodology proved to be efficient and its automation viable, with the VWSE devices made on a lathe at 250 rpm, horizontally with forced drying by a heat blower, presenting the best results among all the devices made. Different vials prepared under the same conditions showed excellent results, with statistical equivalence attested by the T and F tests performed for each alkane. From the evaluation of the viability of the automatic VWSE method, the optimization of the parameters involved in the process was carried out, adopting the optimal conditions of 50 °C during the process, 10 minutes of contact time between sample and extractor phase, 5 minutes of of liquid desorption and 100 μL of extracting solvent used. With the method then defined, a partial validation of the automatic VWSE method was carried out to assess its efficiency, determining its linearity, precision (repeatability and reproducibility), recovery (accuracy) and limits of detection and quantification. The method showed a linear, precise and exact response for the series of alkanes from decane to octadecane, reaching low detection and quantification limit values in the range of μg L-1