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Lesellier E.,CNRS Institute of Organic and Analytical Chemistry | Valarche A.,SEDERE | West C.,CNRS Institute of Organic and Analytical Chemistry | Dreux M.,SEDERE
Journal of Chromatography A | Year: 2012

Due to the renewal of the use of supercritical fluid chromatography (SFC), the coupling of SFC with evaporative light scattering detection (ELSD) needs to be revisited. Indeed, SFC and ELSD apparatus have evolved, while understanding of the nebulisation process has improved. This detector, first developed for polymer analyses can be used for a lot of compounds that do not display sufficient UV absorption. Because the response of ELSD is related to numerous parameters, such as mobile phase composition, the velocity difference between the mobile phase and the nebulisation gas, or the nebulisation temperature, many additional studies are necessary to understand its behaviour in SFC as compared to HPLC. The effects of the nature of co-solvent added to carbon dioxide (methanol, ethanol and acetonitrile), the injected volume and the flow rate on the ELSD response were studied. Certain parameters induce great changes on the nebulisation recovery (the proportion of mobile phase entering the drift tube), allowing for a dramatic improvement in peak area. Moreover, effects of the particle size in the aerosol were also observed, related, as expected, to the modifier nature, but strangely also to the injected volume. Specific and positive behaviour of the ELSD detection on the apparent peak efficiency was confirmed in SFC, for large injected volumes. Finally, a flow rate increase reduces peak area, showing that the use of high flow rates, although attractive to shorten analysis duration, is not favourable to ELSD response. Numerous parameters acting on detector response are modified by the flow rate change, such as the mobile phase velocity. Moreover, measurement of the nebulisation chamber temperature shows the strong decrease of temperature for high flow rates, due to the supercritical fluid depressurisation. © 2012 Elsevier B.V.

Lesellier E.,CNRS Institute of Organic and Analytical Chemistry | Bizet T.,SEDERE | Valarche A.,SEDERE | West C.,CNRS Institute of Organic and Analytical Chemistry | Dreux M.,SEDERE
LC GC Europe | Year: 2012

The use of an evaporative light scattering detector (ELSD) with high performance liquid chromatography (HPLC) has been well documented. However, because the mobile phase is nebulized to produce droplets the use of supercritical fluids as the mobile phase with an ELSD is also favourable because the fluid depressurizes before the detector entrance, which allows the formation of aerosol. This article investigates the ELSD response variation with supercritical carbon dioxide-based mobile phases and compares the response (peak area) with HPLC.

Heron S.,University Paris - Sud | Maloumbi M.G.,University Paris - Sud | Silou T.,Equipe pluridisciplinaire de recherche sur lalimentation et la nutrition EPRAN | Verette E.,SEDERE | And 2 more authors.
Food Analytical Methods | Year: 2010

The goal of this work is to validate a quantitative method to analyze 15 triacylglycerols (TAG) which are present in cucurbitaceous oils using a new liquid chromatography-evaporative light-scattering detector (LC-ELSD) methodology. For the majority of the TAG, the absence of chromophoric groups absorbing in a spectral zone different from those of the high performance liquid chromatography mobile phases limits the use of UV detectors. The most convenient detectors for this type of analyses are the "universal" aerosol-based detectors, and the most frequently used one among these detectors is the ELSD. TAG responses using ELSD can vary according to their structure and the analyst may not possess all the 15 different TAG standards. Therefore, the determination of these analytes in unknown samples cannot be accurate and depends on the nature of the available standards. We propose here a new quantification methodology by LC-ELSD using the standard response model A = a × m b, where a and b are numerical coefficients which are specific for each solute and both correlated. The method uses a sample dilution procedure which provides for each compound to quantify an accurate b value, and by calculation, the corresponding a value. The quantification of both coefficients a and b easily gives the direct mass determination of each TAG. Such LC-ELSD results are validated by the comparison with the fatty acid methyl ester (FAME) analysis using the conventional capillary gas chromatography-flame ionization detector that transforms non-volatile TAG in FAME after a transesterification step. To perform this validation, we compared the experimental FAME composition to the theoretical one calculated from the TAG results obtained by LC-ELSD. For each TAG, theoretical and experimental values were statistically similar, which proves and validates the relevance of the new quantification methodology proposed in this work. The concordance between the two different methods also highlights the great advantage of the direct LC-ELSD method which additionally provides more information on TAG structures. © Springer Science + Business Media, LLC 2009.

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