Thermostatted dual-channel portable capillary electrophoresis instrument.

A new portable CE instrument is presented. The instrument features the concurrent separation of anions and cations in parallel channels. Each channel has a separate buffer container to allow independent optimization of separation conditions. The microfluidics circuit is based on off-the-shelf parts, and can be easily replicated; only four valves are present in the design. The system employs a miniature automated syringe pump, which can apply both positive and negative pressures (-100 to 800 kPa). The application of negative pressure allows a semi-automatic mode of operation for introducing volume-limited samples. The separations are performed in a thermostatted compartment for improved reproducibility in field conditions. The instrument has a compact design, with all components, save for batteries and power supplies, arranged in a briefcase with dimensions of 52 × 34 × 18 cm and a weight of less than 15 kg. The system runs automatically and is controlled by a purpose-made graphical user interface on a connected computer. For demonstration, the system was successfully employed for the concurrent separation and analysis of inorganic cations and anions in sediment porewater samples from Lake Baldegg in Switzerland and of metal ions in a sample from the tailing pond of an abandoned mine in Argentina.

Micro-injector for capillary electrophoresis.

A novel micro-injector for capillary electrophoresis for the handling of samples with volumes down to as little as 300 nL was designed and built in our laboratory for analyses in which the available volume is a limitation. The sample is placed into a small cavity located directly in front of the separation capillary, and the injection is then carried out automatically by controlled pressurization of the chamber with compressed air. The system also allows automated flushing of the injection chamber as well as of the capillary. In a trial with a capillary electrophoresis system with contactless conductivity detector, employing a capillary of 25 µm diameter, the results showed good stability of migration times and peak areas. To illustrate the technique, the fast separation of five inorganic cations (Na(+) , K(+) , NH4 (+) , Ca(2+) , and Mg(2+) ) was set up. This could be achieved in less than 3 min, with good limits of detection (10 µM) and linear ranges (between about 10 and 1000 µM). The system was demonstrated for the determination of the inorganic cations in porewater samples of a lake sediment core.