Strategy for the separation of concentrated samples by capillary electrophoresis

The use of concentrated samples is usually avoided during conventional separations since utilization of concentrated samples normally compromises the quality of separation. However, in case of the detection of low-abundance components, highly concentrated samples are necessary, which leads to an extremely high concentration for high-abundant components. This will make the separation difficult due to the serious longitudinal dispersion. Here, we developed a method to separate high concentration of components based on the modified capillary electrophoresis. The mechanism involves concentrated sample stretched into a wider zone in the higher electric field strength; the sample zone is fractionated into thin sections via a cutting effect; these thin sections are then separated. Based on this mechanism, we examined to separate an overloaded mixture of N,N'-diphenylguanidine and N,N'-di(o-tolyl)guanidine. Baseline separation was achieved due to much small longitudinal dispersion. The theoretical plate numbers of peaks were around 3.5 × 10⁵  m^-1 . The practicality of the new approach is demonstrated in the separation of a model protein mixture, containing lysozyme, bovine serum albumin, and ribonuclease A.