title: Capillary electrophoresis with on-chip four-electrode capacitively coupled conductivity detection for application in bioanalysis.
abstract: Microchip capillary electrophoresis (CE) with integrated four-electrode capacitively coupled conductivity detection is presented. Conductivity detection is a universal detection technique that is relatively independent on the detection pathlength and, especially important for chip-based analysis, is compatible with miniaturization and on-chip integration. The glass microchip structure consists of a 6 cm etched channel (20 microm x 70 microm cross section) with silicon nitride covered walls. In the channel, a 30 nm thick silicon carbide layer covers the electrodes to enable capacitive coupling with the liquid inside the channel as well as to prevent interference of the applied separation field. The detector response was found to be linear over the concentration range from 20 microM up to 2 mM. Detection limits were at the low microM level. Separation of two short peptides with a pI of respectively 5.38 and 4.87 at the 1 mM level demonstrates the applicability for biochemical analysis. At a relatively low separation field strength (50 V/cm) plate numbers in the order of 3500 were achieved. Results obtained with the microdevice compared well with those obtained in a bench scale CE instrument using UV detection under similar conditions.
authors.affiliation: Laboratory of Analytical Biotechnology, Kluyver Institute for Biotechnology, Delft University of Technology, The Netherlands.
authors.forename: R M
authors.initials: RM
authors.lastname: Guijt
authors.forename: E
authors.initials: E
authors.lastname: Baltussen
authors.forename: G
authors.initials: G
authors.lastname: van der Steen
authors.forename: H
authors.initials: H
authors.lastname: Frank
authors.forename: H
authors.initials: H
authors.lastname: Billiet
authors.forename: T
authors.initials: T
authors.lastname: Schalkhammer
authors.forename: F
authors.initials: F
authors.lastname: Laugere
authors.forename: M
authors.initials: M
authors.lastname: Vellekoop
authors.forename: A
authors.initials: A
authors.lastname: Berthold
authors.forename: L
authors.initials: L
authors.lastname: Sarro
authors.forename: G W
authors.initials: GW
authors.lastname: van Dedem
mesh_terms: D002138:Calibration; D002412:Cations / Q000032:analysis; D004553:Electric Conductivity; D004566:Electrodes; D019075:Electrophoresis, Capillary / Q000295:instrumentation / Q000379:methods*; D004867:Equipment Design; D008832:Microchemistry / Q000295:instrumentation / Q000379:methods*; D010455:Peptides / Q000032:analysis; D011189:Potassium Chloride / Q000032:analysis; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002412:Cations; D010455:Peptides; D011189:Potassium Chloride