Mass transport in sub-2-microm high-performance liquid chromatography

Area of Science:

• Analytical Chemistry
• Chromatography Science

Background:

• Ultra-high pressure liquid chromatography (UHPLC) offers enhanced separation speed and efficiency.
• Observed efficiency gains in UHPLC are often less than theoretically predicted.
• The underlying causes for this discrepancy remain largely unknown.

Purpose of the Study:

• To investigate slow analyte desorption from the stationary phase as a potential cause of reduced UHPLC efficiency.
• To quantify the contribution of desorption kinetics to mass transport limitations.

Main Methods:

• Analysis of literature data for reversed-phase elution of acetophenone.
• Variation of particle size (1.7, 3.5, and 5.0 µm) while maintaining constant particle composition and mobile phase.
• Modeling mass transport terms to include desorption as a kinetic factor.

Main Results:

• Mass transport terms across different particle sizes correlated well with a model incorporating analyte desorption.
• An apparent desorption time constant of 2.0 (±0.2) ms was determined for acetophenone.
• The model successfully explained efficiency deviations attributed to desorption.

Conclusions:

• Slow analyte desorption is a significant contributing factor to reduced plate height in UHPLC.
• This finding is particularly relevant for sub-2-micrometer particles commonly used in UHPLC.
• Understanding desorption kinetics can guide the development of more efficient chromatographic materials and methods.