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  • In-channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat.

In-channel amperometric detection for microchip electrophoresis using a wireless isolated potentiostat.

Electrophoresis (2011-03-26)
Dulan B Gunasekara, Matthew K Hulvey, Susan M Lunte
ABSTRACT

The combination of microchip electrophoresis with amperometric detection leads to a number of analytical challenges that are associated with isolating the detector from the high voltages used for the separation. While methods such as end-channel alignment and the use of decouplers have been employed, they have limitations. A less common method has been to utilize an electrically isolated potentiostat. This approach allows placement of the working electrode directly in the separation channel without using a decoupler. This paper explores the use of microchip electrophoresis and electrochemical detection with an electrically isolated potentiostat for the separation and in-channel detection of several biologically important anions. The separation employed negative polarity voltages and tetradecyltrimethylammonium bromide (as a buffer modifier) for the separation of nitrite (NO₂⁻), glutathione, ascorbic acid, and tyrosine. A half-wave potential shift of approximately negative 500 mV was observed for NO₂⁻ and H₂O₂ standards in the in-channel configuration compared to end-channel. Higher separation efficiencies were observed for both NO₂⁻ and H₂O₂ with the in-channel detection configuration. The limits of detection were approximately two-fold lower and the sensitivity was approximately two-fold higher for in-channel detection of nitrite when compared to end-channel. The application of this microfluidic device for the separation and detection of biomarkers related to oxidative stress is described.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Trimethyl-tetradecylammonium chloride, ≥98.0% (AT)
Sigma-Aldrich
Myristyltrimethylammonium bromide, 98% (AT)
Sigma-Aldrich
Myristyltrimethylammonium bromide, ≥99%
Supelco
Myristyltrimethylammonium bromide, suitable for ion pair chromatography, LiChropur, ≥99.0% (AT)