A two-case study of band broadening in liquid chromatography

The effects of band broadening in two chromatographic systems were studied. In the first study the adsorption isotherm of S - Tröger's Base on microcrystalline cellulose triacetate was measured by frontal analysis at several flow rates between 0.2 and 1.2 ml/min. Two chromatographic models were used in order to study the kinetics of mass-transfer between the two phases and to derive plate height values, the equilibrium-dispersive model and the transport model of chromatography. The dependence of the plate height on the flow velocity and on the solute concentration was studied. A modified Van Deemter equation was used to separate the contributions due to slow mass transfer and axial dispersion.

In the second study, column efficiency and plate height were calculated for polystyrene (MW: 1.87 x 10⁶) on a silica column at several flow rates between 1.0 and 100 ml/min. Reduced linear velocities up to 1,000,000 were achieved. The classical Van Deemter equation and an HETP curve were used to analyze the data. The effects of the data acquisition and detector system on the results obtained were also studied.