omation mbers - Society for Laboratory Automation and Screening

5:00 pm Wednesday, February 4 Microfluidics – Detection Room A4
R. Scott Martin
Saint Louis University
3501 Laclede
St. Louis, Missouri 63103
martinrs@slu.edu
Advances in Electrochemical Detection of Neurotransmitters in Microchannels
76
Co-Author(s)
Michelle W. Li, Dana M. Spence,
Nathan A. Lacher, Susan M. Lunte
University of Kansas
It has been shown that electrochemical (EC) detection is an attractive way to analyze neurotransmitters in small
volume biological samples. In recent years, EC detection of neurotransmitters has also been accomplished in
microfabricated devices, usually after separation by capillary electrophoresis (CE). In terms of microchip CEEC,
the separation and detection performance (number of plates, peak skew, and detection limits) has, in general,
been inferior to the most popular detection scheme, laser-induced fluorescence (LIF). Previous studies have
shown this is attributed to the manner in which the electrophoretic voltage is decoupled from the potentiostat.
This presentation will describe the fabrication of a fully integrated palladium decoupler that enables the working
electrode to be isolated from the electrophoretic voltage while remaining in the separation channel. The optimum
decoupler size and decoupler/working electrode spacing was determined using various buffer systems and
field strengths to determine the amount of noise and resolution obtained for the separation of dopamine and
epinephrine. LIF was used to study the amount of band broadening that results from the pressure-induced flow
that occurs past the decoupler. These optimized designs were used for the separation of neurotransmitters with
emphasis on a fully integrated PC-12 cell reactor/microchip CEEC analysis system that enables the separation
and detection of dopamine and norepinephrine released upon Ca 2+ stimulation. Other related work pertaining to
the development of a new method of fabricating carbon electrodes for EC detection in microchannels will also be
described.
8:00 am Thursday, February 5 Microchip – Separations Room A4
Jörg P. Kutter
Technical University of Denmark
DTU, Building, 345 East
Lyngby, DK-2800 Denmark
jku@mic.dtu.dk
Co-Author(s)
Klaus B. Mogensen
Omar Gustafsson
Rikke P. H. Nikolajsen
Capillary Electrochromatography Chip Featuring Sub-micron “Channels” and Integrated
Waveguides
CEC combines the selectivity of liquid chromatography with the efficiency of capillary electrophoresis (CE), and
when miniaturizing CEC, further advantages such as higher efficiency, shorter analysis time, accurate injection
of small volumes, potential for on-chip pre- and post-separation treatment and parallel analyses are gained. We
present a microfluidic separation device for capillary electrochromatography (CEC) featuring integrated waveguides
for optical detection and microfabricated monolithic structures in the separation channel for attaching different
stationary phases. We used an approach similar to the one previously investigated by the Regnier group at Purdue
University, who call the support COMOSS (collocated monolithic support structures). Regnier et al. obtained a
minimum channel width of 1.5 micrometer in quartz. We have developed a process where the channel width
is subsequently reduced by conformal deposition of glass, which enables a channel width of 0.5 micrometer.
Earlier, we have presented a capillary electrophoresis device with monolithically integrated waveguides for
optical detection. The fabrication has been simplified by etching both the optical and fluidic elements in the
same processing step. The chip design allows for both fluorescence and UV/VIS absorbance detection through
integrated waveguides. Also, on-chip gradient elution and various different stationary phases can be realized to
further tune the separation properties. The talk will discuss fabrication issues as well as the performance of the
chip for separations of neutral analytes such as explosives and polycyclic aromatic hydrocarbons, PAH’s.