Stationary phases for packed-column supercritical fluid chromatography

Analysis of fatty acids in foods by supercritical fluid chromatography

Supercritical fluid chromatography (SFC) using formic acid modified carbon dioxide and polymer encapsulated silica based stationary phases is suitable for the analysis with flame ionization detection of organotin compounds of general structure RnSnX4−n where n=4, 3 or 2. For ionic organotin compounds the retention time is independent of the identity of the anion, probably due to the formation of formate salts at the time of injection. A solventless injector is shown to be useful for injecting solvent volumes in the range of 0.5–50 μl, with solvent elimination prior to transferring the sample in the mobile phase to the column and as a simple in-line collection interface for SFC with supercritical fluid extraction (SFE). Various organotin compounds in a marine paint and spiked into a potato or almond matrix were determined on line, by SFE/SFC with flame ionization detection, with a limit of determination of about 1 ppm. The detection limit for typical organotin compounds using the flame ionization detector is about 0.5 ng in the chromatographic system described. SFC using formic acid modified carbon dioxide and flame ionization detection represents a considerable advance in the chromatographic analysis of ionic organotin compounds which are often time consuming and problematic to analyze by other methods.

On-line supercritical fluid extraction and chromatography of organotins with packed microbore columns and formic acid modified carbon dioxide*

The packed capillary column is one type of microcolumn. It is used increasingly in liquid chromatography, supercritical fluid chromatography, and multidimensional chromatography. In order to attain high efficiency with packed capillary columns, reliable column preparation methods must be used. The development of the technique is summarized.

Column technology for packed capillary columns

Ionically Modified Electrodes for Use in Nonpolar Fluids

A newly developed polysiloxane-type packing material shows promise for use in SFC. Relatively polar compounds were eluted from a microbore column with good peakshape using a mobile phase consisting of CO2 modified with formic acid and water. The latter combination is an effective modifier suitable for use with pressure programming and FID detection.

T. L. Yates

Papers

Comparison of packed and capillary columns for practical SFC separations