Fundamental aspects of Solid Phase Micro-Extraction (SPME) are discussed in the present paper. The application of SPME as a microtechnique of sample preparation for gas chromatographic analysis is considered and related to existing theoretical models. Both research prototypes and commercial SPME devices are considered.

This work discusses sample preparation processes for gas chromatography (GC) based on the technique of extraction through membrane permeation (MPE). The MPE technique may be easily coupled to GC via a relatively simple device, which is a module that holds the membrane and is directly connected to the GC column. The possibility of operational errors due to sample handling is substantially reduced in an MPE-GC system because the sample preparation and the chemical analysis are accomplished as a one-step process. The MPE technique is of relatively wide application as it can be used for aqueous samples, solid samples and gaseous samples. Depending on the type of sample the extraction is performed with the membrane in direct contact with the sample or in contact with its headspace. The MPE-GC technique is very useful in trace analysis, due to the time-dependent enrichment of the analyte. A typical application of MPE-GC is the analysis of VOCs present in water that may be accomplished with detection limits at the low ppb (mugL-1) level.

The technique of solid phase microextraction (SPME) was used for the extraction of halogenated contaminants of water samples from three cities of the State of São Paulo and the extracts were submitted to gas chromatographic analysis with electron capture detection (GC-ECD). In the samples of water collected at the city of São Paulo the detected level of trihalomethanes (THM) expressed as the sum of chloroform, dibromochloromethane and dichlorobromomethane, were higher than the permissible limit established by the Brazilian regulation. In the samples collected at the two other cities the level of any of the three THM remained below the sensitivity of the ECD.

Foi estudada a aplicabilidade do método de calibração independente de composto para a análise cromatográfica de quatro trialometanos (THM) com detecção por um Detector por Emissão Atômica em Plasma de Hélio Induzido por Microondas (MIP). A sistemática usada se baseou na comparação de curvas de calibração construídas para os quatro THM monitorando o sinal nas raias de emissão de cloro e carbono. Os resultados desses estudos também permitiram avaliar a utilidade do detector MIP para a análise dos THM em concentrações ambientais típicas.

The applicability of the compound independent calibration method for the chromatographic analysis of four trihalomethanes (THM) after detection with a Microwave Induced Helium Plasma Atomic Emission Detector (MIP) was studied. The approach used was based on comparison of calibration curves constructed for the THM after monitoring the MIP signal at a carbon emission line and a chlorine emission line. The results of these studies also allowed evaluation of the usefulness of the MIP detector for the analysis of the THM at typical concentration levels of environmental concern.

Foi estudada a independência da resposta de um Detector por Emissão Atômica Induzida em Plasma de Microondas utilizando-se nove compostos organoclorados como amostra de teste. Com ajuste apropriado das condições operacionais do equipamento, monitorando os sinais na linha de emissão do cloro em 479,5 nm, para os nove compostos foram obtidas respostas concordantes ao nível de 8,5% ou menos, o que é adequado para uso do método de calibração independente do composto. Propõe-se que a confiabilidade da quantificação com a metodologia de calibração independente do composto pode ser melhorada, se um conjunto de compostos é usado em lugar de um único composto de calibração.

The independence of the response of a Microwave Induced Plasma Atomic Emission Detector (GC-MIP) for Gas Chromatography with the chemical structure of the analyte has been exploited using as teste samples nine organochlorine compounds. With signal monitoring at the chlorine 479.5 nm emission line and after proper adjustment of the operational conditions of the GC-MIP the agreement of the detector response for the nine compounds was of 8.5% or less, which is adequate for the use of the compound-independent calibration method. It is proposed that the reliability of the quantitation after applying the compound-independent calibration methodology may be enhanced if a set of calibration compounds is used instead of a single calibration compound.

Two models of a glass micro-extractor were constructed after modification of a model proposed in the literature. The two models were used for the simultaneous extraction and enrichment of organochlorinated pesticides from aqueous matrixes to an organic solution appropriate for the gas chromatographic analysis of the pesticide. It was established that the performance of one of the modified micro-extractors permits the pre-concentration of the pesticides to a level that allow their quantitation at the trace level with electron capture detection. It is thus concluded that the glass micro-extractor is a suitable tool for the sample preparation step in the gas chromatographic analysis of environmental pollutants of the class of pesticides.