SOME VARIABLES AFFECTING REPRODUCIBILITY IN CAPILLARY ELECTROPHORESIS

Several variables that can affect reproducibility of both the peak hei ght and the migration time in capillary electrophoresis (CE) were inve stigated here. A great part of the imprecision in CE for migration tim e is related to the interaction of the analyte with the capillary wall . Within a run, acidic compounds with long migration times have a high er relative standard deviation. In general, conditions that decreased the migration time, such as a short capillary length, tended to enhanc e the reproducibility of the migration time. Sample size also affected the reproducibility of peak height. Too small or too large an injecti on volume diminished the reproducibility. Sample matrix, such as high levels of proteins or salts in the sample, decreased the reproducibili ty. Furthermore, improvement in reproducibility can be achieved by usi ng internal standards (especially for migration time), thorough washin g of the capillary, or removing the excess proteins by acetonitrile de proteinization. Acetonitrile has an added effect of producing sample s tacking. Depending on the migration time and analyte concentration, th e peak height and area yielded different reproducibility results.