Krishnat P. Naikwadi

Polyacrylate liquid crystalline stationary phases in supercritical fluid chromatography with carbon dioxide mobile phase

SummaryNew polyacrylate liquid crystalline compounds were coated onto glass or fused-silica capillary columns as stationary phases and applied to supercritical fluid chromatography. These stationary phases, were very stable: no bleeding was observed at 200°C and up to 200kg/cm2 pressures of carbon dioxide mobile phase. The wide working range of the capillary column was extended below the g-n transition temperature. Isomeric compounds such as α- and β-methoxynaphthalene, anthracene and phenanthrene and several phenolic compounds were separated.

New liquid crystalline stationary phases for gas chromatography of positional and geometrical isomers having similar volatilities

New liquid crystalline compounds of the type 2-methyl-4′-R-4-(p-methoxycinnamoyloxy)azobenzene, where R = methoxy, ethoxy, ethyl or n-butyl, were synthesized. Their properties as stationary phases for the gas chromatographic separation of positional isomers of xylene, dichlorobenzene, methoxynaphthalene and geometrical isomers of insect sex pheromones of similar volatilities have been investigated. The effect of temperature on the separation ability of the liquid crystalline compounds was studied. Large separation factors, α, for isomers were obtained on a column in its supercooled nematic state. The separation of insect sex pheromones was found to depend on the structure of the liquid crystalline compound used as stationary phase rather than on its nematic range.

Ion chromatography of nucleobases, nucleosides and nucleotides using a dual-detection system

Abstract The retention behaviour of nucleobases, nucleosides, and nucleotides has been systematically investigated using ion chromatography with a hollow fibre ion-exchange membrane suppressor. A low-capacity anion-exchange resin column and sodium carbonate buffer or sodium phosphate buffer eluents were employed for the separation of these compounds. The effects of concentration and pH of the mobile phase on the retention behaviour of twelve nucleotides was studied in detail. A conductivity detector was used for the detection of inorganic anions as well as organic compounds along with a UV detector. Optimum conditions for the rapid separation of nucleobases, nucleosides, nucleotides and their mixtures using carbonate and phosphate buffers are reported.

Liquid chromatography of isomers of aromatic acids on microbore column packed with anion-exchange resin

SummaryA low-capacity, anion-exchange, porous-polymer resin was used as the packing material in a microbore column. Using a phosphate buffer containing various organic modifiers, retention behavior of substituted benzoic acid isomers with amino, chloro, methyl, nitro and carboxylic groups was investigated. The effect of ethanol, acetonitrile and sodium dodecylsulfate used as organic modifiers on the retention behavior at various eluent pH values was studies and optimum separations of the positional isomers reported.