Mathematical Model Describing Gradient Focusing Methods for Trace Analytes
详细信息 查看全文
- 作者：Sandip Ghosal and Jon Horek
- 刊名：Analytical Chemistry
- 出版年：2005
- 出版时间：August 15, 2005
- 年：2005
- 卷：77
- 期：16
- 页码：5380 - 5384
- 全文大小：79K
- 年卷期：v.77,no.16(August 15, 2005)
- ISSN：1520-6882
文摘
The problem of gradient focusing for concentrating traceanalytes is considered. Variation of buffer viscosity,conductivity, and possibly also the 
-potential results ina focusing point where the electrophoretic velocity isbalanced by the electroosmotic flow (EOF) and where thesample concentrates. The axial inhomogeneity also resultsin an induced pressure gradient that alters the EOF profileand therefore causes Taylor dispersion. The coupledhydrodynamics and transport problem leading to theachievement of a steady state is studied in the context ofthe lubrication approximation: all variations in the axialdirection take place over a length scale very much largerthan the characteristic channel width. A single length scale
m and a single time scale 
is found to completelydetermine the dynamics of the evolution close to thefocusing point. Using appropriate scaled variables, thetime evolution of the concentration profile near equilibrium can be described by an inhomogeneous advectiondiffusion equation that is free of all parameters. Explicitformulas are deduced for the location of the peak centroidand its width as a function of time. A simple graphicalmethod is proposed for optimizing the performance of thesystem when some tunable external parameters are available.
-potential results ina focusing point where the electrophoretic velocity isbalanced by the electroosmotic flow (EOF) and where thesample concentrates. The axial inhomogeneity also resultsin an induced pressure gradient that alters the EOF profileand therefore causes Taylor dispersion. The coupledhydrodynamics and transport problem leading to theachievement of a steady state is studied in the context ofthe lubrication approximation: all variations in the axialdirection take place over a length scale very much largerthan the characteristic channel width. A single length scalem and a single time scale is found to completelydetermine the dynamics of the evolution close to thefocusing point. Using appropriate scaled variables, thetime evolution of the concentration profile near equilibrium can be described by an inhomogeneous advectiondiffusion equation that is free of all parameters. Explicitformulas are deduced for the location of the peak centroidand its width as a function of time. A simple graphicalmethod is proposed for optimizing the performance of thesystem when some tunable external parameters are available.