High-salt stacking principles and sweeping: comments and contrasts on mechanisms for high-sensitivity analysis in capillary electrophoresis

High-salt stacking in electrokinetic chromatography (EKC) is defined and contrasted to the sweeping method. A recent paper argued the two methods are identical, where high concentrations of micelle in the sample were intended to mimic the effect of high-salt stacking. However, high micelle concentration in the sample matrix in EKC is analogous to using a high-conductivity sample instead of a low-conductivity sample in field amplified stacking. High-salt stacking does not require a sample free of pseuostationary phase, only a sample with a high-mobility co-ion compared to the separation buffer electrokinetic vector. High-salt stacking uses a discontinuous buffer system and should not be confused with continuous buffer stacking systems such as sweeping.