Fast electrophoresis in conventional capillaries by employing a rapid injection device and contactless conductivity detection

A purpose-made set-up featuring an automated fast injector allowed the easy optimization of the injected amount and the adjustment of the separation length of conventional capillaries from a minimum of 5 cm upward. It was found that a compromise in capillary length for separation effciency and analysis time also has to take into account the injected amount, which in turn affects the sensitivity and hence the detection limit. The versatility of the system was demonstrated by the analysis of the major cations and anions in natural water samples in less than 1 min, the concurrent determination of a mixture of amino acids and carbohydrates in 160 s, and of three active ingredients in a pharmaceutical preparation in 40 s. Plate numbers were typically around 50,000 and detection limits down to 1 mu M could be achieved.