The difficulties encountered in quantitative analysis by gas chromatography are discussed, with particular reference to detection systems. The properties of an ideal detector for quantitative analysis are listed. A description is given of the mode of operation of detectors for gas chromatography, and the extent to which they are suitable for quantitative work is assessed. It was concluded that no one detector possessed all the properties required or an ideal detector. In particular a qualitative knowledge of the sample for analysis was required by all detectors; and calibration was required by the majority of detectors. The extent to which the Brunel mass detector overcomes these limitations was assessed. It is shown that the response of the mass detector depends solely on weight changes caused by adsorption of materials eluted from the chromatographic column thus completely eliminating the need for calibration and qualitative information. The response of the detector is integral, so that the problems associated with peak area measurement do not arise. The sensitivity of the detector is of a similar order to conventional hot wire detectors. The detector gave a quantitative response to all materials analysed, covering a wide boiling range: the upper limit was determined by the maximum column operating temperature, and the lower limit by the extent to which the detector was cooled. The detector responded quantitatively to water. At room temperature the detector responded on a qualitative basis to organic and inorganic gases. The detector was used for the calibration of other detector, and was operated in conjunction with the Martin gas density balance to determine the molecular weights of eluted materials.

Solos apresentam hidrocarbonetos gasosos em quantidades variáveis e acredita-se que as formações de reservatórios de óleo podem ser detectáveis indiretamente utilizando-se bactérias no solo capazes de degradá-los. O presente estudo teve como objetivo caracterizar comunidades microbianas envolvidas com o metabolismo desses hidrocarbonetos. As amostras de solo Np (área não petrolífera) e Solo P (área petrolífera) foram analisadas através da construção de bibliotecas do gene RNAr 16S de bactérias e arquéias e de genes catabólicos que codificam enzimas monooxigenases solúveis (SDIMO). As comunidades apresentaram estrutura diferente em relação aos grupos de bactérias e arqueias e análise dos genes catabólicos indicou maior riqueza e diversidade no solo P. A maior parte do clones se mostrou filogeneticamente mais próxima de sequências de enzimas de bactérias não cultivadas proveniente de amostras ambientais. Análises de cromatografia gasosa realizadas logo após a coleta detectaram maiores níveis de metano no solo P e maiores níveis de etano e propano no solo Np. A técnica de PCR quantitativo (Real Time PCR) mostrou um número maior de cópias do rRNA 16S no solo Np, mas não foi eficiente em quantificar os genes degradadores de gases leves presentes no solo. / Gaseous hydrocarbons occur in sub-surface soil in highly variable amounts and oil reservoirs formations are supposed to be indirectly detectable through soil microbial populations capable of consuming it. The goal of the present work was to characterize microbial communities involved in short-chain alkane metabolism in soils in and off sedimentary basin areas (named P and Np soil, respectively). Three clone libraries were constructed for each sample, one 16S rRNA gene library for each of the Domains Bacteria and Archaea, and one for the catabolic gene coding for the soluble di-iron monooxygenase (SDIMO) enzyme. Bacterial and archaeal communities structures were different between the samples. Analysis of the catabolic genes presented higher values of richness and diversity in soil P. The sequences from soil samples were more closely related to each other than to reference sequences. Short-chain hydrocarbon measures performed just after samples were collected showed higher levels of methane and lower levels of ethane and propane in soil P in comparison to soil Np. A real-time PCR method was not successful in yielding the catabolic gene quantification suggesting that such genes occur in very low abundance in the soil samples under study.

Solos apresentam hidrocarbonetos gasosos em quantidades variáveis e acredita-se que as formações de reservatórios de óleo podem ser detectáveis indiretamente utilizando-se bactérias no solo capazes de degradá-los. O presente estudo teve como objetivo caracterizar comunidades microbianas envolvidas com o metabolismo desses hidrocarbonetos. As amostras de solo Np (área não petrolífera) e Solo P (área petrolífera) foram analisadas através da construção de bibliotecas do gene RNAr 16S de bactérias e arquéias e de genes catabólicos que codificam enzimas monooxigenases solúveis (SDIMO). As comunidades apresentaram estrutura diferente em relação aos grupos de bactérias e arqueias e análise dos genes catabólicos indicou maior riqueza e diversidade no solo P. A maior parte do clones se mostrou filogeneticamente mais próxima de sequências de enzimas de bactérias não cultivadas proveniente de amostras ambientais. Análises de cromatografia gasosa realizadas logo após a coleta detectaram maiores níveis de metano no solo P e maiores níveis de etano e propano no solo Np. A técnica de PCR quantitativo (Real Time PCR) mostrou um número maior de cópias do rRNA 16S no solo Np, mas não foi eficiente em quantificar os genes degradadores de gases leves presentes no solo. / Gaseous hydrocarbons occur in sub-surface soil in highly variable amounts and oil reservoirs formations are supposed to be indirectly detectable through soil microbial populations capable of consuming it. The goal of the present work was to characterize microbial communities involved in short-chain alkane metabolism in soils in and off sedimentary basin areas (named P and Np soil, respectively). Three clone libraries were constructed for each sample, one 16S rRNA gene library for each of the Domains Bacteria and Archaea, and one for the catabolic gene coding for the soluble di-iron monooxygenase (SDIMO) enzyme. Bacterial and archaeal communities structures were different between the samples. Analysis of the catabolic genes presented higher values of richness and diversity in soil P. The sequences from soil samples were more closely related to each other than to reference sequences. Short-chain hydrocarbon measures performed just after samples were collected showed higher levels of methane and lower levels of ethane and propane in soil P in comparison to soil Np. A real-time PCR method was not successful in yielding the catabolic gene quantification suggesting that such genes occur in very low abundance in the soil samples under study.