Influence of viscous friction heating on the efficiency of columns operated under very high pressures

Journal Article · Thu Jan 01 04:00:00 EST 2009 · Analytical Chemistry

DOI:https://doi.org/10.1021/ac802632x· OSTI ID:1041459

Gritti, Fabrice ^[1]; Guiochon, Georges A ^[2]

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1. University of Tennessee, Knoxville (UTK)
2. ORNL

When columns packed with very fine particles are operated at high mobile phase velocities, the friction of the mobile phase percolating through the column bed generates heat. This heat dissipates along and across the column and axial and radial temperature gradients appear. The wall region of the column tends to be cooler than its center, and due to the influence of temperature on the mobile phase viscosity and on the equilibrium constant of analytes, the band velocity is not constant across the column. This radial heterogeneity of the temperature distribution across the column contributes to band broadening. This phenomenon was investigated assuming a cylindrically symmetrical column and using the general dispersion theory of Aris, which relates the height equivalent to the theoretical plate (HETP) contribution due to a radial heterogeneity of the column to the radial distribution of the linear velocities of a compound peak and to the radial distribution of its apparent dispersion coefficients in the column bed. The former is known from the temperature gradient across the column, the temperature dependencies of the mobile phase viscosity, and the retention factor of the compound. The latter is derived from the known expression of the transverse reduced HETP equation for the column. The values of the HETP calculated with the Aris model and a classical HETP equation were compared to those measured on a 2.1 x 50 mm Acquity BEH-C{sub 18} column, run at flow rates of 0.6, 0.95, 1.30, and 1.65 mL/min, with pure acetonitrile as the mobile phase and naphtho[2,3-a]pyrene as the retained compound. These two sets of data are in generally good agreement, although the experimental values of the HETP tend to increase faster with increasing mobile phase velocity than the calculated values.

• Research Organization: Oak Ridge National Laboratory (ORNL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-00OR22725
• OSTI ID: 1041459
• Journal Information: Analytical Chemistry, Journal Name: Analytical Chemistry Journal Issue: 9 Vol. 81; ISSN 0003-2700
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
ACETONITRILE
DISPERSION RELATIONS
EFFICIENCY
FLOW RATE
FRICTION
HEAT EXCHANGERS
HEATING
PHASE VELOCITY
PLATES
RETENTION
SPATIAL DISTRIBUTION
TEMPERATURE DISTRIBUTION
TEMPERATURE GRADIENTS
VELOCITY
VISCOSITY