Open-tubular columns for liquid and supercritical fluid chromatography

Sammanfattning: Methods have been developed for the preparation of narrow-bore open tubularcolumns. In this content, condensed gases (butane, chloroethane and Freon114) were used as solvents for the static coating of these columns. Adevice for filling the narrow-bore open tubular columns with solutions incondensed gases has been designed.The effect of repeated cross-linking of SE-54 stationary phase, usingazo-rerr.-butane as radical initiator, on the chromatographic properties ofthe columns has been studied. Excessive repetition of the immobilizationadversely affected the chromatographic properties. Optimal conditions forthe immobilization of Carbowax 20M stationary phase using Desmodur L75 andDesmodur N75 as cross-linking reagents have been determined.Properties of immobilized Carbowax 20M stationary phase have beeninvestigated under LC and GC conditions at room and moderately increasedtemperatures. Glass transition temperature of the stationary phase has beenestimated. Significant changes in stationary phase selectivity anddiffusivity, dependent on the reagent applied for stationary phasecross-linking, have been found at temperatures below the glass transitiontemperature. Swelling of the immobilized stationary phase film with water -methanol mobile phases has been studied at different temperatures. Theeffect of the degree of swelling on the column retention and efficiency hasbeen estimated. Significant increase in diffusion coefficients in thestationary phase swollen with methanol at room temperature has beenobserved.Improvements have been made of an apparatus for measurement of diffusioncoefficients in supercritical carbon dioxide, with regard to the injection,the separation of a solute from a solvent and the back-pressure device. Anoptimization procedure has been used for the estimation of diffusioncoefficients of some test solutes.A selective ion-exchange stationary phase has been synthesized in situ innarrow-bore columns and, after loading with silver ions, used forargentation supercritical fluid chromatography. Good selectivity towardsunsaturated compounds has been demonstrated.