Contactless conductivity detector for microchip capillary electrophoresis

Martin Pumera, Joseph Wang, František Opekar, Ivan Jelinek, Jason Feldman, Holger Löwe, Steffen Hardt

Research output: Contribution to journalArticlepeer-review

209 Citations (Scopus)


A microfabricated electrophoresis chip with an integrated contactless conductivity detection system is described. The new contactless conductivity microchip detector is based on placing two planar sensing aluminum film electrodes on the outer side of a poly(methyl methacrylate) (PMMA) microchip (without contacting the solution) and measuring the impedance of the solution in the separation channel. The contactless route obviates problems (e.g., fouling, unwanted reactions) associated with the electrode-solution contact, offers isolation of the detection system from high separation fields, does not compromise the separation efficiency, and greatly simplifies the detector fabrication. Relevant experimental variables, such as the frequency and amplitude of the applied ac voltage or the separation voltage, were examined and optimized. The detector performance was illustrated by the separation of potassium, sodium, barium, and lithium cations and the chloride, sulfate, fluoride, acetate, and phosphate anions. The response was linear (over the 20 μM-7 mM range) and reproducible (RSD = 3.4-4.9%; n = 10), with detection limits of 2.8 and 6.4 μM (for potassium and chloride, respectively). The advantages associated with the contactless conductivity detection, along with the low cost of the integrated PMMA chip/detection system, should enhance the power and scope of microfluidic analytical devices.

Original languageEnglish
Pages (from-to)1968-1971
Number of pages4
JournalAnalytical Chemistry
Issue number9
Publication statusPublished - 2002 May 1

All Science Journal Classification (ASJC) codes

  • Analytical Chemistry


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