Automated microgradient system for capillary electrochromatography

A microprocessor controlled gradient elution system suitable for capillary electrochromatography has been developed and tested. It is based on a liquid handling device described previously which is capable of liquid transport with both low and high fluid dispersion. The low dispersion region formed by stainless steel needle 250 microm I.D. serves for sample injection, while the high dispersion region, created by steep extension of tube diameter, is used for continuous mobile phase gradient generation. A homologous series of seven alkylphenones was electrochromatographically separated on a monolithic polyacrylic column under gradient conditions. An S-shaped acetonitrile gradient (30-70%) was applied. A high reproducibility of retention times (RSD about 0.1%) was obtained, indicating accuracy of automated gradient operations.