title: Vacancy capillary zone electrophoresis and differential capillary zone electrophoresis:  variations on a well-known theme.
abstract: Two new variants on capillary zone electrophoresis (CZE) are described and experimentally investigated. In vacancy CZE the sample, diluted with a background electrolyte, fills the electrode vessels and the separation capillary. When pure background electrolyte is injected, the resulting electropherogram represents the composition of the sample. The electropherogram is almost identical with the result of a conventional CZE experiment. In differential CZE the sample again fills the electrode vessels and the separation compartment. After injection of a slightly different sample, a differential electropherogram is obtained that represents the differences between the two samples. The retention times of both new variants are comparable with conventional CZE, the separation efficiency, in terms of theoretical plates, is marginally lower, and both show good quantitative characteristics. The concept of vacancy electrophoresis explains the origin of unexpected system peaks in conventional CZE when multiple co-ions in the background electrolyte are used.
authors.affiliation: Nederlandse Philips Bedrijven, Centre for Manufacturing Technology, SAQ 1766, P.O. Box 218, 5600 MD Eindhoven, The Netherlands.
authors.forename: F E
authors.initials: FE
authors.lastname: Mikkers