Headspace mass spectrometry methodology: application to oil spill identification in soils.

In the present work we report the results obtained with a methodology based on direct coupling of a headspace generator to a mass spectrometer for the identification of different types of petroleum crudes in polluted soils. With no prior treatment, the samples are subjected to the headspace generation process and the volatiles generated are introduced directly into the mass spectrometer, thereby obtaining a fingerprint of volatiles in the sample analysed. The mass spectrum corresponding to the mass/charge ratios (m/z) contains the information related to the composition of the headspace and is used as the analytical signal for the characterization of the samples. The signals obtained for the different samples were treated by chemometric techniques to obtain the desired information. The main advantage of the proposed methodology is that no prior chromatographic separation and no sample manipulation are required. The method is rapid, simple and, in view of the results, highly promising for the implementation of a new approach for oil spill identification in soils.

Surfactant cloud point extraction and preconcentration of organic compounds prior to chromatography and capillary electrophoresis.

The use of preconcentration steps based on phase separation by the cloud point technique offers a convenient alternative to more conventional extraction systems. It has been used successfully for the preconcentration of species of widely differing character and nature, such as metal ions, proteins and other biomaterials, or organic compounds of strongly differing polarity. Here we address the most recent analytical applications of this methodology when used as an isolation and trace enrichment step prior to the analysis of organic compounds (polycyclic aromatic hydrocarbons, polychlorinated compounds, pesticides, phenolic derivatives, aromatic amines, vitamins, etc.) via liquid and gas chromatography or capillary electrophoresis.

Automated on-line membrane extraction liquid chromatographic determination of phenols in crude oils, gasolines and diesel fuels.

Determination of phenols in crude oils and derived fuels requires a sample pretreatment step, usually performed by liquid-liquid extraction or preparative chromatography. In this work, sample preparation is accomplished using a silicone membrane separation unit coupled on-line to a high performance liquid chromatograph with amperometric and ultraviolet detection. The contents of phenol, cresols and dimethylphenols were determined in thirty three samples including three crude oils, twenty gasolines and ten diesel fuels. The whole set-up is fully automated through a feed-back system that allows the microcomputer controlling the process to examine the signals in real time and to make decisions while the experiment is running.

Cloud point preconcentration of rather polar compounds: application to the high-performance liquid chromatographic determination of priority pollutant chlorophenols.

The potential of the cloud point methodology for the preconcentration of relatively polar compounds was studied using the non-ionic surfactant Triton X-114 and five EPA chlorophenols as test analytes. Analyte determination was performed using reversed-phase gradient LC with electrochemical and spectrophotometric detection. The amount of surfactant used is a critical variable in the preconcentration factor because it determines the extraction yield and the volume of surfactant-rich phase obtained. These values were determined as a function of the Triton X-114 concentration, together with the phase ratio, which allows prediction of the maximum preconcentration factor under given conditions.