Sensitivity models in simulation of capillary zone electrophoresis: the effect of buffer power and initial buffer concentration.

Separation of proteins by capillary zone electrophoresis in an amphoteric medium is investigated by numerical simulation. We explain how sensitivity models can be used to gain further information about this process. The sensitivity models that are derived are used to study the sensitivity of the separation to the specific buffer capacity of the amphoteric molecule that serves as a buffer. The effect of changing the overall concentration of this ampholyte is also examined and it is shown that a change in its concentration is equivalent to a change in its buffer capacity.

Protein separation by electrophoresis in a nonsieving amphoteric medium.

A numerical model has been used to study the separation of protein mixtures by zone electrophoresis in a nonsieving amphoteric medium. An amphoteric buffer fixes the pH of the solution close to its isoelectric point, where the buffer molecules are unchanged: they thus contribute very little to the conductivity of the solution. This means that high field strengths can be used for rapid separation without sacrificing resolution. The numerical study shows that in this process the band spreading that can reduce resolution is essentially due to differences in migration rate between protein-rich and low-protein zones: both differences in solution conductivity and in protein mobility are involved. Rules for judging the buffer capacity of amphoteric molecules are presented and it is shown how, for a given protein, the effectiveness of this technique varies with the range of pH in which it is applied.