Investigations on the calculation of the third moments of elution peaks. II—Linear flow speed dependence of external mass transfer coefficient

• The external mass transfer coefficient of a compound was derived from its band third moment.
• This coefficient increases linearly with increasing mobile phase velocity.
• The contribution of surface diffusion to this coefficient was assessed.
• The results are consistent with the predictions of the General Rate model.

This work is a systematic investigation of the linear velocity dependence of the external mass transfer coefficient provided by fitting experimental results to the solution of the GR (General Rate) model that was previously derived. The second and third statistical moments of eluted peaks were measured at different flow rates, under different experimental conditions and analyzed. The results of this analysis confirm the validity of this dependence under our current experimental conditions. The other mass transfer parameters provided by the GR model were determined. The variations of these parameters with the experimental conditions were measured. The results are discussed and interpreted.