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Dive into the research topics where Paul G. Vahey is active.

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Featured researches published by Paul G. Vahey.


Talanta | 2000

Development of a positive pressure driven micro-fabricated liquid chromatographic analyzer through rapid-prototyping with poly(dimethylsiloxane) : Optimizing chromatographic efficiency with sub-nanoliter injections

Paul G. Vahey; Sang Hyun Park; Brian J. Marquardt; Younan Xia; Lloyd W. Burgess; Robert E. Synovec

A rapid and low-cost means of developing a working prototype for a positive-displacement driven open tubular liquid chromatography (OTLC) analyzer is demonstrated. A novel flow programming and injection strategy was developed and implemented using soft lithography, and evaluated in terms of chromatographic band broadening and efficiency. A separation of two food dyes served as the model sample system. Sample and mobile phase flowed continuously by positive displacement through the OTLC analyzer. Rectangular channels, of dimensions 10 mum deep by 100 mum wide, were micro-fabricated in poly-dimethylsiloxane (PDMS), with the separation portion 6.6 cm long. Using a novel flow programming method, in contrast to electroosmotic flow, sample injection volumes from 0.5 to 10 nl were made in real-time. Band broadening increased substantially for injection volumes over 1 nl. Although underivatized PDMS proved to be a sub-optimal stationary phase, plate heights, H, of 12 mum were experimentally achieved for an unretained analyte with the rectangular channel resulting in a reduced plate height, h, of 1.2. Chromatographic efficiency of the unretained analyte followed the model of an OTLC system limited by mass-transfer in the mobile phase. Flow rates from 6 nl min(-1) up to 200 nl min(-1) were tested, and van Deemter plots confirmed plate heights were optimum at 6 nl min(-1) over the tested flow rate range. Thus, the best separation efficiency, N of 5500 for the 6.6 cm length separation channel, was achieved at the minimum flow rate through the column of 6 nl min(-1), or 3 ml year(-1). This analyzer is a low-cost sampling and chemical analysis tool that is intended to complement micro-fabricated electrophoretic and related separation devices.


Analytical Chemistry | 1999

A Raman Waveguide Detector for Liquid Chromatography

Brian J. Marquardt; Paul G. Vahey; Robert E. Synovec; Lloyd W. Burgess


Talanta | 1999

Reversed phase liquid chromatography with UV absorbance and flame ionization detection using a water mobile phase and a cyano propyl stationary phase Analysis of alcohols and chlorinated hydrocarbons.

Wes W. C. Quigley; Scott T Ecker; Paul G. Vahey; Robert E. Synovec


Analytical Chemistry | 2002

Toward a fully integrated positive-pressure driven microfabricated liquid analyzer.

Paul G. Vahey; Sean A. Smith; Colin D. Costin; Younan Xia; Anatol M. Brodsky; Lloyd W. Burgess; Robert E. Synovec


Archive | 2010

Methods and systems for using IR spectroscopy to quantify degradation of wiring insulation

Steven Kenneth Brady; Paul H. Shelley; Paul G. Vahey


Archive | 2012

Resin detection system

Paul H. Shelley; Paul G. Vahey; Gregory J. Werner; Gabor J. Kemeny; Gard Groth; Gina Stuessy; Natalie Ann Crothers


Archive | 2008

Thermal effect measurement with near-infrared spectroscopy

Paul H. Shelley; Gregory J. Werner; Paul G. Vahey


Archive | 2011

System and method for resin thickness measurement

Paul H. Shelley; Gregory J. Werner; Paul G. Vahey


Archive | 2011

Method of predicting thermal or chemical effect in a coated or painted composite material

Paul H. Shelley; Gregory J. Werner; Paul G. Vahey


Analytical Chemistry | 2000

Nanoparticle Characterization in Nanoliter Volumes by Grating Light Reflection Spectroscopy

Sean A. Smith; Anatol M. Brodsky; Paul G. Vahey; Lloyd W. Burgess

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Younan Xia

University of Washington

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Sang Hyun Park

University of Washington

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Scott T Ecker

University of Washington

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