Influence of the distortion of gradient profile on peak width in gradient liquid chromatography

In gradient liquid chromatography, the gradient profile may be distorted because of the effects of solvent mixing and axial dispersion. Such effects will be significant especially when stepwise gradient and linear gradient with high slope are applied. In this work, we discussed the influence of the distortion of gradient profile on the peak width. Firstly, the chromatographic peaks were measured under linear and stepwise gradient conditions where a C18 column was used as the stationary phase, a mixture of methanol and water as the mobile phase, and biphenyl and acetophenone as the samples. Then, the response of methanol under corresponding conditions was recorded by disconnecting the column and the detection wavelength was set at 205 nm. The gradient profile at the column inlet was calculated from the methanol response profile. The theoretical values of the peak width were calculated from the set gradient profile and the gradient profile obtained at the column inlet respectively. The theoretical values were compared with the experimental ones. It is shown that the distortion of gradient profile does affect the peak width. When such influence is taken into account, the theoretical and experimental values of the peak width are well consistent.