An organic-inorganic hybrid material was fabricated by the sol-gel method and cast as a thin glass film onto the inner walls of fused silica capillary columns. The thin film in the capillaries functioned as the stationary phase for reversed phase open tubular liquid chromatography (OTLC) and open tubular electrochromatography (OTEC). The stationary phase provides high surface area and thus an improved phase ratio. Multiple preparation steps are avoided by attaching the stationary phase and increasing the surface area in a single procedure. By adjusting the ratio of the monomeric precursors in the original sol-gel solution, the retentive characteristics of the stationary phase are controlled. This new approach facilitates column preparation for OTLC and OTEC. Capillary columns prepared in this manner showed retention characteristics superior to conventionally prepared ones. Polycyclic aromatic hydrocarbons were used to evaluate the stationary phase; under the experimental conditions used, efficiencies of 204 000-285 000 and 280 000-500 000 plates/m were observed in OTLC and OTEC, respectively. The sol-gel-derived stationary phase was shown to be stable under acidic and basic conditions.Open tubular liquid chromatography (OTLC) and open tubular electrochromatography (OTEC) have shown a great potential to reach high efficiencies for the analysis of complex sample mixtures.1™3 The preparation of the stationary phase is of key importance to achieve the high performance offered by these(1) Dorsey,

Capillary zone electrophoresis (CZE) was employed to separate sugars according to their electrophoretic mobilities In strong alkaline solutions (pH ca. 13). Saccharide zones were monitored electrochemlcally using amperometric detection at a constant potential, 0.6 V (vs Ag/AgCI), with a cylindrical copper wire electrode (25 pm In diameter). The Cu-wlre microelectrode In strong basic solutions had electrochemical behavior similar to that of Cu electrodes with larger dimensions and appeared to show no deterioration for hundreds of runs. A sample mixture containing 15 different sugars was separated In less than 45 min with separation efficiencies up to 200 000 theoretical plates. The calibration plot was found to be linear over 3 orders of magnitude and the limits of detection for the saccharides studied were In the femtomole range.

Carbon dots (C-dots) are often synthesized, modified, and studied as a mixture. Unfortunately, the spectroscopic and biological properties measured for such C-dots assume that there is a high degree of homogeneity in the produced sample. By means of high-resolution separation techniques, we show that "as-synthesized" C-dots exist as a relatively complex mixture and that an unprecedented reduction in such complexity can reveal fractions of C-dots with unique luminescence properties. The wavelength-dependent photoluminescence commonly assigned as an inherent property of C-dots is not present in fractionated samples. While ultraviolet-visible absorption profiles reported for C-dots are typically featureless, we have found fractions of C-dots possessing unique absorption bands, with different fractions possessing specific emission wavelengths. Furthermore, fractionated C-dots showed profound differences in emission quantum yield, allowing for brighter C-dots to be isolated from an apparent low quantum yield mixture. These more luminescent fractions of C-dots displayed improved biological compatibility and usefulness as cellular imaging probes.

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