Abstract: A procedure is developed for the determination of citrate ions in blood plasma by capillary zone electrophoresis at a level of 20‒800 mg/L. The background electrolyte (BGE) was a solution containing 10 mM chromate ions and 40 mM diethanolamine. Sample preparation included protein precipitation with acetonitrile, followed by dilution with a solution containing an internal standard (fluoride ion), and centrifugation. It is shown that the use of the internal standard ensures the account of the change in the migration time of the analyte in the analysis of biological samples. The relative standard deviation of analysis does not exceed 10% for two replicate determinations. The systematic error of the developed procedure was evaluated by the added–found method.