High temperature normal phase liquid chromatography of aromatic hydrocarbons on bare zirconia.

The normal phase HPLC behavior of a bare zirconia column was studied at temperatures up to 200 °C using a hexane mobile phase. The use of elevated column temperatures significantly decreased the retention of twenty five aromatic model compounds according to the van't Hoff equation (>30-fold decrease for some compounds). Large improvements in peak shape, efficiency (>2.

Fast supercritical fluid chromatography hydrocarbon group-type separations of diesel fuels using packed and monolithic columns.

Two approaches for decreasing diesel hydrocarbon group-type separation times by normal phase supercritical fluid chromatography (SFC) are compared. Short (10-15 cm) columns with small 3 microm diameter packing are compared with monolithic Chromolith bare silica columns under high carbon dioxide flow rates approaching 5 ml min(-1). Elution times are reduced up to 13-fold on a 10 cm Chromolith column and 7-fold on the short packed columns compared with conventional length columns run at typical flow rates.

Comparison of titania, zirconia, and silica stationary phases for separating diesel fuels according to hydrocarbon group-type by supercritical fluid chromatography.

Silica, zirconia, and titania columns were compared for their ability to separate diesel samples into saturates, mono-, di-, tri-, and polyaromatics by supercritical fluid chromatography (SFC) using pure CO(2) according to ASTM method D 5186-03. A titania column coupled in series to a silica column was found to provide the highest overall group-type resolutions based on 20 model compounds, with resolutions as high as 14.7 for saturates versus monoaromatics and 11.

Selective fluorometric detection of polyamines using micellar electrokinetic chromatography with laser-induced fluorescence detection.

The polyamines putrescine, cadaverine, spermine and spermidine were separated and quantified by micellar electrokinetic chromatography (MEKC) with laser-induced fluorescence detection. The derivatization reagent, 1-pyrenebutanoic acid succinimidyl ester (PSE), allowed for the selective detection of the polyamines at 490 nm. Multiple labeling of the polyamines with PSE allows the formation of intramolecular excimers that emit at longer wavelengths (450-520 nm) than mono-labeled analytes (360-420 nm).