Investigations on analyte losses in systems suited for large-volume on-column injections |
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Authors: | M Adahchour E M Kristenson R J J Vreuls U A Th Brinkman |
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Institution: | (1) Department of Analytical Chemistry and Applied Spectroscopy, Vrije Universiteit, de Boelelaan 1083, 1081 HV Amsterdam, the Netherlands |
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Abstract: | Summary Use of a large-volume injection system with a solvent vapour exit (SVE) requires optimisation. An appropriate strategy is
to determine the evaporation rate by increasing the injection time at a fixed injection speed, injection temperature and head
pressure. When measuring the flow rate in the carrier gas supply line to the on-column injector, optimisation can be very
rapid: some five injections of pure solvent will be sufficient.
When working under partially concurrent solvent evaporation conditions, loss of volatiles is often observed if no retaining
precolumn is used between the retention gap and the SVE. To investigate the requirements (length and stationary phase) of
the retaining precolumn, C8–C18n-alkanes inn-hexane were used. The minimum length of the retaining precolumn (0.32 mm diameter) needed to prevent substantial losses of
volatiles was 2 m. Experiments with retaining precolumns with and without stationary phase gave identical results. This shows
that there is no need to coat the capillary as it only acts as a restrictor. |
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Keywords: | Column liquid chromatography Gas chromatography Large-volume injection On-column injection Evaporation rate Retaining precolumn |
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