title: Development of a photothermal absorbance detector for use with microfluidic devices.
abstract: The development of a photothermal absorbance detector for use with microfluidic devices is described. Unlike thermo-optical techniques that rely on measuring refractive index changes, the solution viscosity is probed by continuously monitoring solution conductivity. Platinum electrodes microfabricated on a quartz substrate and bonded to a substrate containing the microchannels enable contact conductivity measurements. The effects of excitation frequency and voltage, electrode spacing, laser power, and laser modulation (chopping) frequency were evaluated experimentally. In the current configuration, a limit of detection of 5 nM for DABSYL-tagged glucosamine was obtained using long injections (to give flat-topped peaks). This corresponds to an absorbance of 4.4 x 10(-7) AU. Separation and detection of DABSYL-tagged glycine, proline, and tryptophan are also shown to demonstrate the feasibility of the method. In addition, simulations were used to investigate the applicability of the technique to small volume platforms.
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapman Hall Room 251, Chapel Hill, North Carolina 27599-3216, USA.
authors.forename: Patty J
authors.initials: PJ
authors.lastname: Dennis
authors.forename: Erin Ferguson
authors.initials: EF
authors.lastname: Welch
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Alarie
authors.forename: J Michael
authors.initials: JM
authors.lastname: Ramsey
authors.forename: James W
authors.initials: JW
authors.lastname: Jorgenson
mesh_terms: D000042:Absorption / Q000528:radiation effects*; D004553:Electric Conductivity; D004566:Electrodes; D019075:Electrophoresis, Capillary / Q000379:methods; D005998:Glycine / Q000737:chemistry; D007834:Lasers; D008027:Light; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D011392:Proline / Q000737:chemistry; D012212:Rheology / Q000379:methods; D014364:Tryptophan / Q000737:chemistry
chemical_list: D014364:Tryptophan; D011392:Proline; D005998:Glycine
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