The influence of nonuniform coating and taylor dispersion on the evaluation of capillary column inverse gas chromatography

A mathematical model which takes into account the combined effect of Taylor dispersion and film eccentricity on the elution profiles has been developed for the analysis of a capillary column inverse gas chromatography (CCIGC) experiment. In this paper, we present an additional improvement on the model presented by Hamdan et al. [E. Hamdan, J.F. Milthorpe, J.C.S. Lai, J. Chromatogr. A, 1078 (2005) 144] to include the effect of coating nonuniformity. The new model shows that while Taylor dispersion effect has a very significant effect on the elution profiles at low values of β and γ, the general effect of film asymmetry is to reduce this effect. At sufficiently large γ and/or β values, Taylor dispersion effect becomes negligible and the elution profiles will be mainly affected by film asymmetry. The inclusion of Taylor dispersion effect will increase the variance of the elution curves which could significantly affect the estimated value of the diffusivity Dp. The error in the estimated Dp values obtained using the Pawlisch et al. [C.A. Pawlisch, J.R. Bric, R.L. Laurence, Macromolecules 21 (1988) 1685] nonuniform model increases as γ and/or β are reduced and when the coated polymer exhibits less deviation from uniform films.