On-column capillary flow cell utilizing optical waveguides for chromatographic applications

Abstract

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.

Design and performance of a light‐emitting diode detector compatible with a commercial capillary electrophoresis instrument

“…In photometric detection in CE using LEDs it has been shown that it is the stray light (light which reaches the detector without passing through the detection window) that is the key parameter which mostly determines detector linearity, rather than a lack of an ideally monochromatic light source [15]. While a number of approaches can be used to evaluate detector linearity [15,[27][28][29], in this study we followed the approach of Macka et al [15] by measuring the response (absorbance) of a series of standard solutions in order to calculate sensitivity (absorbance/concentration). Sensitivity was then plotted against absorbance to determine the absorbance value at which sensitivity began to decrease from its maximum value.…”

Determination of thermodynamic properties by supercritical fluid chromatography

“…The capillary flow cells with optical fibres were used successfully in liquid-phase separation techniques such as electrophoresis [250] and high-temperature HPLC [251]. Bruno et al [252] developed a capillary flow cell with optical fibres for use in open tubular column SFC. On the basis of a ray tracing algorithm, they formulated the guidelines for selecting proper diameters of the source and the collecting fibres to fit a particular capillary tube.…”

On-Chip Capillary Electrophoresis (Chip-CE) with Optical On-Chip Leaky-Waveguide-Based Detection

“…One problem with the bubble is that different light rays traverse the bubble via very different paths, some with no interaction with the fluid at all, others with an optical interaction length equal to the full inner bubble diameter, to mention only both extremes. Another concept employs U-or Z-cells, where the middle part of the U or of the Z is used as an optical path [4]- [7]. But typically U-or Z-cells have larger inner channel diameters than the capillary itself and are extra parts of the separation column, which have to be physically attached to the capillary somehow.…”