PhD Oral Examination annoucement

Tarun khurana at stanford.edu
Mon Jun 30 13:36:22 PDT 2008


University Ph.D. Oral Examination

Title:  On-Chip Isotachophoresis Assays for High Sensitivity  
Electrokinetic Preconcentration, Separation and Indirect Fluorescence 
Detection

Candidate: Tarun Khurana

Advisor: Prof. Juan G. Santiago
Department of Mechanical Engineering

Time: Wednesday,  July 2nd  2008,  2:00 pm

refreshments served at 1:45 pm

Location: McCullough building, room 122 (map attached)


Abstract:
Microfluidic devices have been particularly attractive for separation 
based chemical and biological analysis since the small length scales 
bring fundamental improvements in reagent volume, analysis time, 
resolution and separation efficiency.  However, smaller length scales 
and volumes are also associated with lower detection sensitivity and 
therefore, microchip electrophoresis analysis is often less sensitive 
and is more commonly used for fluorescent analytes since fluorescence 
detection platform offers higher sensitivity.  This presentation will 
focus on leveraging an electrophoresis technique termed isotachophoresis 
(ITP) for improving the detection sensitivity of on-chip electrophoresis 
assays and extending its scope to non-fluorescent analytes.
    ITP is a robust sample preconcentration technique focuses analytes 
into zones that are ~10 µm wide. Such extreme compression of analytes 
results in drastic improvement in the detection sensitivity and 
resolution of electrophoretic separation system.  We present a 
theoretical and experimental study of dynamics of ITP preconcentration 
that helps identify and optimize experiment parameters to achieve high 
sample preconcentration      We have also demonstrated an indirect 
detection technique based on ITP to detect non fluorescent analytes on a 
standard fluorescence detection platforms.  We leverage ITP to 
preconcentrate and separate analytes into distinct analyte zones and use 
a set of fluorescent species with different electrophoretic mobilities 
to demarcate the boundaries of these analyte zones and thereby, 
indirectly detect the non-fluorescent analytes present.  We obtain ~1 µM 
detection sensitivity with this assay with high repeatability and have 
demonstrated indirect detection of a variety of analytes such as amino 
acids, organic acids and environmental toxins such as phenols and cresol.






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