30) Pace, C. F.; Thornberg, S. M.; Maple, J. R. Appl. Spechosc. 1988, (31) Wiilis, B. G.; Woodruff, W. H.; Frysinger, J. R.; Margerum, D. w.; Par-(32) Meiling, G. E.; Pardue, H. L.The high separatlon efficiencies provided by various chromatographic technlques employlng microbore and capillary columns, countered by current detection llmltatlons, present new challenges In detection cell design. I n thls contrlbution we descrlbe a device sultable for on-column simultaneous absorption and fluorescence detection that utlllzes optical waveguides. The deslgn of this cell is based upon the aMlty of a capmary to functlon as a strongly focuskrg lens along one of Its axes. I n order to use thls attribute to the fullest advantage, a three-dimensional ray tracing algorithm, which sbnuiates the optlcal phenomena at the Interfaces and In the travellng media, was developed. Thus, from a trial set composed of commercially available components, we were able to choose optkal flber/capillary tube geometric configurations that yielded theorellcai transmittances of ca. 90%. Subsequent lmphmtatbn of the cell In capillary supercrltical flukl chromatography led to verlflcatlon of these flndlngs. Statlc and dynamlc refractive index effects, which are known to dlstort recording signals, were carefully Investigated and mlnimlzed. Two guldeHnes based upon experimental and theoretical observations are formulated-the first statlng the maxhnum source mer dlameter for a given choke of cap#lary tube and the second relating the minlmum dlameter of the co#ectlng fiber to an already chosen source Hber and caplllary tube-enabilng rapld selection of the cell optical hardware.

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An alternative phase deliverysystem based on piston pumps and a back-pressure regulator has been developed for capillary column SFC.Thechromatographyis not affected bythefast piston pump refill. A homogeneous on-line mixing of binary phases with simultaneous pressure programming is easily accessible without any additional computing. Acceptable reproducibilitiesMethod development requires the capability of fast change in modifier concentration or exchange of mobile phase components. Therefore, an on-line phase mixing is preferred rather than an off-line procedure.In principle, pressure (density), temperature, and mobile phase composition gradients can influence the separanon process in CSFC cases, the usefulness of composltlon gradents in CSFC has not yet been shown However, results in packed column SFC show (< 3.5% RSD for external and < 2.0% RSD for internal standard methods) were found with mixtures of P-propanol/CO* as mobile phases using UV detection and split ratios of 1 :GO and 1 :120.Variation and control ofthesplit areeasilydone bysimple flow rate volumetric changes.

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