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Joule heating in packed capillaries used in capillary electrochromatography
Anurag S Rathore1, Kimberly J Reynolds, Luis A Colón
1Technology Development, Bioprocess and Formulation Technology, Pharmacia Co., Chesterfield, MO 63198, USA. anurag.s.rathore@pharmacia.com
Electrophoresis
|September 11, 2002
Summary
Joule heating in capillary electrochromatography (CEC) columns can significantly impact separation efficiency. This study reveals that heat dissipation is often inefficient, leading to elevated column temperatures and affecting reproducibility.
Area of Science:
- Analytical Chemistry
- Separation Science
- Electrochemistry
Background:
- Effective heat dissipation is crucial for reproducible and efficient separations in electrically driven systems like capillary electrochromatography (CEC).
- Temperature variations in the mobile phase affect flow rate, retention kinetics, and analyte diffusion, impacting separation outcomes.
- Joule heating, generated by electrical current, is a significant factor influencing mobile phase temperature within CEC columns.
Purpose of the Study:
- To investigate the extent of Joule heating in packed capillary columns used in CEC.
- To assess the efficiency of heat dissipation in CEC columns under typical operating conditions.
- To quantify the temperature increase within CEC columns due to Joule heating.
Main Methods:
- Measured electrical conductivity of various mobile phases at different temperatures to determine temperature coefficients.
- Measured electrical current at varying applied voltages to calculate in-column conductivity as a function of voltage.
- Utilized established theories for modeling Joule heating effects in capillary electrophoresis (CE) to estimate column temperatures.
Main Results:
- An increase in conductivity with applied voltage indicated Joule heating and inefficient heat dissipation.
- Calculated elevated temperatures within packed CEC columns, exceeding ambient by over 23°C under specific conditions.
- Observed even higher temperature increases (approx. 35°C) in open capillary columns under similar conditions.
Conclusions:
- Heat dissipation in CEC columns is not always efficient, particularly with poor thermal conducting packing materials.
- Joule heating can lead to significant temperature increases within the column, potentially compromising separation reproducibility.
- The findings align with recent experimental data from NMR thermometry and Raman spectroscopy.