Automated dual capillary electrophoresis system with hydrodynamic injection for the concurrent determination of cations and anions
The capillary electrophoresis instrument developed for the concurrent determination of cations and anions features two separate capillaries and individual detectors to allow independent optimization for each group of ions. The capillaries are joined in a common injector block. The sample is drawn into the injector with a small membrane pump and automated simultaneous injection into both capillaries is achieved by pressurization of the fluid with compressed air. Flushing of the injector and of the capillaries with the background electrolyte is also carried out automatically by the same means. The buffer consisted of 12mM histidine and 2mM 18-crown-6 adjusted to pH 4 with acetic acid and was suitable for the contactless conductivity detection employed. The system was optimized for the determination of cationic NH4 + and anionic NO3- and NO2-, and linear calibration curves from about 20μM up to about 1.5mM were obtained for these ions. In a test run over 8h, the reproducibil...