Gradient elution in micellar liquid chromatography. I. Micelle concentration gradient.

Gradient elution in micellar liquid chromatography (MLC) is discussed. On the basis of the gradient elution theory, first developed by Snyder, equations were derived for the prediction of gradient retention times in micelle concentration gradient from isocratic data. Likewise, partition coefficients into micelles and stationary phase, and subsequently isocratic retention at different micelle concentrations can be estimated from two gradient runs. However, more studies need to be done to achieve better agreement between isocratic and gradient data. The equations will be useful for efficient development of practical separations by MLC.

Gradient elution in micellar liquid chromatography. II. Organic modifier gradients.

The application of organic modifier gradients in micellar liquid chromatography (MLC) is discussed. The equation derived by Snyder and co-workers describing gradient elution in hydro-organic reversed-phase LC was verified for organic solvent gradients in the presence of micelles. It is also demonstrated that the use of these gradients require little re-equilibration time due to the limited range of organic modifier concentration used in the gradient. This would result in shorter analysis time. Lastly, a practical application of the use of propanol and acetonitrile gradients in MLC is described.