A preliminary study of the chromatographic performance and permeability of a continuous silica xerogel column under reversed-phase HPLC conditions was performed. A porous chromatographic support was synthesized inside a 0.32 mm i.d. × 13 cm fused silica tube from potassium silicate solution and derivatized with dimethyloctadecylchlorosilane. The plate height at 0.01 cm/s (0.5 μL/min), near the apparent optimum linear velocity, was about 65 μm. The column efficiencies in terms of numbers of plates per meter were 5000 and 13 000 for ethyl benzoate (k = 0.8) and naphthalene (k = 2.0), respectively, at 0.5 μL/min. The major parameter affecting column efficiency was the heterogeneous morphology of the xerogel, modifications to which are expected to improve chromatographic performance. The column provided efficiencies comparable to those reported for continuous polymeric columns but less than that previously reported for a continuous silica column. Gradient elution mode was demonstrated with a mixture of polycyclic aromatic hydrocarbons. The column was highly permeable, exhibiting a linear dependence of pressure to flow rate and a back pressure of only 632 psi at 10 μL/min when a 95% aqueous mobile phase was used.

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Variations In tha refractive Index of low critical temperature, highly compressible mobile phases were observed which are not seen In capMary-ceU ultraviolet-absorption detection with high critical temperature, low compressibility supercritical mobile phases In capMary supercritical fluid chromatography (SFC). Changes In base line apparently resulting from density-related refractive Index changes were reduced to acceptable levels by cooling the detector cell. The system Is sensitive and useful In studies of mixed mobile phases In capillary SFC. An 8.9 mol % mixture of 2-propanol or nltromethane In C02 produced significant decreases In retention of polar and nonpolar polycyclic aromatic compounds. The 2-propanol/C02 mobile phase effected the elution of ovalene at moderate temperature and pressure.

The application of capillary isotachophoresis (CITP) and combined CITP-mass spectrometry (MS) for peptides and proteins is demonstrated. Separation of simple peptide mixtures, as well as enzymatic digets of proteins, is also reported using CITP with UV detection. The potential utility of CITP for proteins is demonstrated. Initial studies of combined CITP-MS of enzymatic digests is also demonstrated, showing the potential for rapid sequence determination.

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