Capacitively coupled contactless conductivity detection with dual top–bottom cell configuration for microchip electrophoresis

Abstract

An optimized capacitively coupled contactless conductivity detector for microchip electophoresis is presented. The detector consists of a pair of top-bottom excitation electrodes and a pair of pickup electrodes disposed onto a very thin plastic microfluidic chip. The detection cell formed by the electrodes is completely encased and shielded in a metal housing. These approaches allow for the enhancement of signal coupling and extraction from the detection cell that result in an improved signal-to-noise-ratio and detection sensitivity. The improved detector performance is illustrated by the electrophoretic separation of six cations (NH(4) (+), K(+), Ca(2+), Na(+), Mg(2+), Li(+)) with a detection limit of approximately 0.3 microM and the analysis of the anions (Br(-), Cl(-), NO(2) (-), NO(3) (-), SO(4) (2-), F(-)) with a detection limit of about 0.15 microM. These LODs are significantly improved compared with previous reports using the conventional top-top electrode geometry. The developed system was applied to the analysis of ions in bottled drinking water samples.

Monolithic integration of fine cylindrical glass microcapillaries on silicon for electrophoretic separation of biomolecules

“…A mixture of FITC-labeled three amino acid molecules (Ser, Gly, and Gln) was loaded into a representative device in which five out of ten microcapillaries (6)(7)(8)(9)(10) were filled with the running buffer. Their electropherograms obtained at the detection point (1 mm from reservoir BW) are shown along with a fluorescence image of the microcapillaries in Fig 5(a).…”

“…Over the years, microcapillary electrophoresis (lCE) 1 has been evolved with numerous innovations addressing a particular aspect of the original concept such as microfabrication, 2 sample injection, 3 separation speed, 4 separation efficiency, 5 integrated sample preparation, 6 and analyte detection. 7 Substantial progress has been made towards the commercialization of the technology for laboratory and point-of-care use. 8 Yet, few important issues have remained to be addressed: (1) excessive Joule heating through the capillary; (2) non-uniform zeta potential (f) on the capillary walls and the accompanying unstable electroosmotic flow (EOF); (3) depletion of analytes to the capillary walls due to analyte-surface interactions; and (4) challenges with the fabrication techniques such as etching, alignment, and substrate bonding to integrate the capillary.…”

Determination of chloride, sulfate and nitrate in drinking water by microchip electrophoresis

“…Although we can see significant efforts in developments of MCE [7,12,14,[16][17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33][34][35], applications of this technology in analytical practice are still rather scarce. For example, in the field of water analysis only a limited number of relevant papers can be found [7,16,[24][25][26][27]32].…”

In‐plane alloy electrodes for capacitively coupled contactless conductivity detection in poly(methylmethacrylate) electrophoretic chips

“…As C 4 D electrodes are physically insulated from the solution by a layer of material, they offer several advantages over contact electrodes including prevention of electrode fouling and the associated increase in electrode working life and the isolation from the separation voltage, eliminating the risk of bubble generation. Gold , platinum , copper and other metals or alloys are commonly employed as C 4 D electrode materials due to their excellent conductivity and other material properties that have seen their widespread use in many precision electronic applications. A conductive polymer, polyaniline (PANI), was also incorporated onto a microchip as the electrode material .…”