Otimização e aplicação da microextração em fase sólida com e sem refrigeração interna em amostras de ervas medicinais e água de rio

Abstract

A microextração em fase sólida no modo de extração headspace (HS-SPME) e a microextração em fase sólida com recobrimento internamente refrigerado no modo headspace (HS-CF-SPME) foram utilizadas para a determinação do perfil volátil de amostras de ervas medicinais comumente encontrados no sul do Brasil. Otimizações multivariadas permitiram o estabelecimento das condições de extração para ambos procedimentos e as análises foram feitas por cromatografia gasosa. Foi testada a utilização de duas temperaturas da fibra no mesmo procedimento de extração, sendo posteriormente comparados os procedimentos, tendo a estratégia baseada em utilizar duas temperaturas da fibra apresentado melhor desempenho levando em conta a totalidade de compostos. A utilização de dois modos de extração (imersão direta e headspace) e duas temperaturas de extração em um mesmo procedimento de SPME para a determinação simultânea de trihalometanos e pesticidas organoclorados em amostras aquosas também foi estudada. Otimizações multivariadas para a escolha das melhores formas de extração (headspace e imersão direta) forma aplicadas. A partir desta otimização foi construída a curva de calibração para os compostos estudados sendo obtidos resultados satisfatórios quanto aos parâmetros analíticos de mérito e a aplicabilidade foi testada em amostras de água do rio Araranguá - SC.<br>

Abstract : The solid phase microextraction in headspace extraction mode (HSSPME) and internally-cooled-solid phase microextraction in headspace mode (HS-CF-SPME) were used for determining the volatile profile in samples of herbs commonly found in southern Brazil, such as sage, artichoke, fennel, peppermint, macela and chamomile. Multivariate optimizations allowed the determination of the extraction conditions for both procedures and analyzes were performed by gas chromatography with flame ionization detector (GC-FID) the responses were the geometric means of extracted compounds. The optimized conditions for the HS-SPME procedure were 60 °C and 40 min respectively for temperature and extraction time. For the HS-CF-SPME procedure the optimized condition was extraction temperature 60 °C and the extraction time of 15 min with the fiber coating temperature optimized at 5 °C. The use of two fiber temperatures in the HS-CF-SPME procedure in order to extract volatile and semi-volatile compounds has been optimized , were used 60 °C in first 7.5 min and 5 °C in 7.5 min remaining, on a total extraction time of 15 min. Both procedures HS-CF-SPME were compared, and the HS-CF-SPME procedure with one fiber temperature performed better only for the more volatile compounds, and the strategy of using two fiber temperatures showed better performance for all compounds. It was also possible to determine the volatile profile of each herb studied by this sample praparation technique using gas chromatography and mass spectrometry (GC-MS). The use of two extraction modes (direct immersion and headspace) and two extraction temperatures in the same SPME procedure to simultaneous determination of trihalomethanes (THM) and organochlorine pesticides in aqueous samples was studied. Multivariate optimizations for the choice of the best extraction conditions (headspace and direct immersion) so applied. Regarding the use of two modes of simultaneous extraction in a single extraction procedure, the ideal conditions were extraction time of 70 min, 28 min in the HS-SPME mode at 12 °C (favoring the extraction of THM) and 42 min in the DISPME mode at 80 °C (favoring the extraction of organochlorine pesticides). From this optimization was made a calibration curve for the compounds studied were obtained correlation coefficients above of 0.98; percentage of recovery between 90.8 - 103.7% and relative standard deviations between 11.4 e 17.9%, both this dates were obtained to concentrations of 20 ?g.L-1 being the arithmetic mean of triplicates (n=3). After, this procedure was applied in water samples collected from the river Araranguá - SC.