title: Automated dual capillary electrophoresis system with hydrodynamic injection for the concurrent determination of cations and anions.
abstract: 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 reproducibility for the peak areas was within ±7%. For demonstration, the instrument was successfully applied to the concurrent monitoring of the concentrations of the three ions during the biological removal of ammonium from contaminated groundwater in a sequencing batch reactor, where NO3(-) and NO2(-) are formed as intermediate products.
authors.affiliation: University of Basel, Department of Chemistry, Spitalstrasse 51, Basel 4056, Switzerland; Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi, Viet Nam.
authors.forename: Thi Thanh Thuy
authors.initials: TT
authors.lastname: Pham
authors.affiliation: University of Basel, Department of Chemistry, Spitalstrasse 51, Basel 4056, Switzerland; Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi, Viet Nam.
authors.forename: Thanh Duc
authors.initials: TD
authors.lastname: Mai
authors.affiliation: Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi, Viet Nam.
authors.forename: Thanh Dam
authors.initials: TD
authors.lastname: Nguyen
authors.affiliation: Department of Analytical Chemistry, Physical Chemistry and Chemical Engineering - University of Alcalá, Ctra. Madrid-Barcelona km 33.6, Alcalá de Henares, Madrid 28871, Spain.
authors.forename: Jorge
authors.initials: J
authors.lastname: Sáiz
authors.affiliation: Centre for Environmental Technology and Sustainable Development (CETASD), Hanoi University of Science, Nguyen Trai Street 334, Hanoi, Viet Nam. Electronic address: phamhungviet@hus.edu.vn.
authors.forename: Hung Viet
authors.initials: HV
authors.lastname: Pham
authors.affiliation: University of Basel, Department of Chemistry, Spitalstrasse 51, Basel 4056, Switzerland. Electronic address: Peter.Hauser@unibas.ch.
authors.forename: Peter C
authors.initials: PC
authors.lastname: Hauser
keywords: Anions; Capacitively coupled contactless conductivity detection (C(4)D); Cations; Dual-capillary electrophoresis; Simultaneous separations