Taylor dispersion analysis in coiled capillaries at high flow rates

Area of Science:

• Analytical Chemistry
• Fluid Dynamics
• Physical Chemistry

Background:

• Taylor Dispersion Analysis (TDA) traditionally uses straight capillaries.
• High flow rates in coiled capillaries induce complex flow dynamics, including vortices.
• Existing models struggle to explain experimental observations in coiled systems.

Purpose of the Study:

• To investigate analyte band broadening in long, coiled capillaries at high flow rates.
• To develop an empirical scaling equation for predicting band width.
• To apply the technique for determining diffusion coefficients of diverse analytes.

Main Methods:

• Performing Taylor Dispersion Analysis (TDA) in long, coiled capillaries.
• Analyzing the gaussian distribution of analyte concentration at the capillary outlet.
• Developing an empirical scaling equation based on experimental data.

Main Results:

• High flow rates in coiled capillaries generate vortices, leading to convective mixing.
• Analyte band width is significantly reduced compared to straight capillaries.
• An empirical scaling equation was determined, relating band width to flow rate, diffusion, viscosity, and capillary dimensions.

Conclusions:

• Coiled capillaries enhance mixing and reduce band broadening in TDA.
• The derived scaling equation offers a versatile tool for various capillary sizes and parameters.
• The technique was successfully applied to determine diffusion coefficients for a wide range of molecules.