MilliporeSigma
  • Home
  • Search Results
  • Metalless electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips.

Metalless electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips.

Electrophoresis (2015-03-27)
Gerson F Duarte Junior, José Alberto Fracassi da Silva, Kelliton José Mendonça Francisco, Claudimir Lucio do Lago, Emanuel Carrilho, Wendell K T Coltro
ABSTRACT

This paper describes the use of ionic solutions as sensing electrodes for capacitively coupled contactless conductivity detection on electrophoresis microchips. Initially, two channels were engraved in a PMMA holder by using a CO2 laser system and sealed with a thin adhesive membrane. PDMS electrophoresis chips were fabricated by soft lithography and reversibly sealed against the polymer membrane. Different ionic solutions were investigated as metalless electrodes. The electrode channels were filled with KCl solutions prepared in conductivity values from approximately 10 to 40 S/m. The best analytical response was achieved using the KCl solution with 21.9 S/m conductivity (2 mol/L). Besides KCl, we also tested NaCl and LiCl solutions for actuating as detection electrodes. Taking into account the same electrolyte concentration (2 mol/L), the best response was recorded with KCl solution due to its higher ionic conductivity. The optimum operating frequency (400 kHz) and the best sensing electrode (2 mol/L KCl) were used to monitor electrophoretic separations of a mixture containing K(+) , Na(+) , and Li(+) . The use of liquid solutions as sensing electrodes for capacitively coupled contactless conductivity detection measurements has revealed great performance to monitor separations on chip-based devices, avoiding complicated fabrication schemes to include metal deposition and encapsulation of electrodes. The LOD values were estimated to be 28, 40, and 58 μmol/L for K(+) , Na(+) , and Li(+) , respectively, what is comparable to that of conventional metal electrodes. When compared to the use metal electrodes, the proposed approach offers advantages regarding the easiness of fabrication, simplicity, and lower cost per device.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Sodium chloride solution, 0.85%
Sigma-Aldrich
Potassium chloride, AnhydroBeads, −10 mesh, 99.99% trace metals basis
Sigma-Aldrich
Lithium chloride, AnhydroBeads, −10 mesh, ≥99.9% trace metals basis
Sigma-Aldrich
Lithium chloride, AnhydroBeads, −10 mesh, 99.998% trace metals basis
Sigma-Aldrich
Potassium chloride, ≥99.99% trace metals basis
Sigma-Aldrich
3-Ethyl-2,4-pentanedione, mixture of tautomers, 98%
Sigma-Aldrich
Lithium chloride, powder, ≥99.98% trace metals basis
Sigma-Aldrich
Potassium chloride, AnhydroBeads, −10 mesh, 99.999% trace metals basis
Sigma-Aldrich
Sodium chloride, AnhydroBeads, −10 mesh, 99.99% trace metals basis
Sigma-Aldrich
Sodium chloride, AnhydroBeads, −10 mesh, 99.999% trace metals basis
Sigma-Aldrich
Potassium chloride, 99.999% trace metals basis
Sigma-Aldrich
Sodium chloride-35Cl, 99 atom % 35Cl
Sigma-Aldrich
Sodium chloride, random crystals, optical grade, 99.9% trace metals basis
Sigma-Aldrich
Sodium chloride, 99.999% trace metals basis
Sigma-Aldrich
Sodium hydroxide, BioUltra, for luminescence, ≥98.0% (T), pellets
Sigma-Aldrich
Sodium hydroxide solution, BioUltra, for molecular biology, 10 M in H2O
Sigma-Aldrich
Sodium sulfate, ≥99.99% trace metals basis
SAFC
L-Histidine
Sigma-Aldrich
Sodium sulfate, BioUltra, anhydrous, ≥99.0% (T)
Sigma-Aldrich
Sodium chloride solution, 0.9% in water, BioXtra, suitable for cell culture
Sigma-Aldrich
Sodium chloride, tablet
Sigma-Aldrich
Sodium sulfate, BioXtra, ≥99.0%
Sigma-Aldrich
L-Histidine, suitable for cell culture, meets EP, USP testing specifications, from non-animal source
Sigma-Aldrich
Sodium chloride, for molecular biology, DNase, RNase, and protease, none detected, ≥99% (titration)
Sigma-Aldrich
L-Histidine, ReagentPlus®, ≥99% (TLC)
Sigma-Aldrich
Sodium chloride, BioXtra, ≥99.5% (AT)
Sigma-Aldrich
Lithium chloride, BioXtra, ≥99.0% (titration)
Sigma-Aldrich
Lithium chloride, for molecular biology, ≥99%
Sigma-Aldrich
Sodium hydroxide solution, 1.0 N, BioReagent, suitable for cell culture
Sigma-Aldrich
Sodium chloride solution, 5 M in H2O, BioReagent, for molecular biology, suitable for cell culture