Imaging of electrophoretic flow across a capillary junction

Abstract

We have designed a simple system to allow visualization of electroosmotlc flow across a capillary junction. Two capillaries are placed In close proximity by careful micropositioning, and the distance between the capillaries Is controlled with submicron resolution. The Junction thus produced Is placed at the focal point of a stereomicroscope, where the Image collected by the microscope Is Imaged onto a CCD camera. Illumination of the Junction (Immersed In a buffer solution) allows visualization of the electroosmosis of a dye across the liquid Junction. This has allowed the determination of the dimensional characteristics of the Junction and the optimization of the composition of the buffer bathing the Junction, thereby allowing efficient transfer of a sample across a 50-200-jum gap.

Post‐column derivatization in narrow‐bore capillaries for the analysis of amino acids and proteins by capillary electrophoresis with fluorescence detection

“…This diffusional advantage is somewhat analogous to the more effective heat dissipation observed with the use of smaller capillaries in CE [2]. Analytes will also diffuse out of the gap; however, outward diffusion on analytes may be counteracted for ionic analytes by electric field effects [39]. After a zone of solution passes into the reaction capillary, diffusion should be sufficient to thoroughly mix derivatizing reagents with analytes before the analytes reach the detector.…”

“…Effect of gap distance on reactor performance. Gap alignment and gap distance are important factors in the transfer of reagents into the reaction capillary and in the transfer of analytes across the gap, especially with high ionic strength buffers [39]. The effect of gap size on reactor performance has been examined using gaps ranging from 4 to 160 pm in distance.…”

“…Using dansyl arginine as a neutral marker, electroosmotic flow with OPA reagent (p is equal to has been found to be 7% less than that with only borate buffer (pm is equal to [7.00 0.041 x cm2 V-' s-l). Therefore, the volume flow rate should be slightly lower (less than 7% difference) [39] in the reaction capillary since the OPA derivatizing buffer is introduced at the gap. A previous post-column gap reactor described by Albin et al [30] used a reaction capillary that was larger than the separation capillary (75 pm i.d.…”

Recent applications of capillary electrophoresis–mass spectrometry (CE–MS): CE performing functions beyond separation

“…Developments in CE and CE-MS-based integrated systems are highlighted in the following. Kuhr and co-workers were among the first to develop enzymatic capillary reactors for online protein digestion [122][123][124][125]. Trypsin was immobilized through biotin-avidin binding onto the inner wall of a 50 m i.d.…”

Characterization of fluid transport in microscale structures

“…There are a number of examples of flow imaging which have employed the introduction of a constant stream or plug of dye into capillaries as a means to image the zone fiont 111, 2,3]. The use of a dye allows imaging of flow through gel-filled [4], particle packed arid open microchannel systems.…”