COMBINATION OF FLOW-INJECTION WITH CAPILLARY ELECTROPHORESIS - PART-3- ONLINE SORPTION COLUMN PRECONCENTRATION CAPILLARY ELECTROPHORESIS SYSTEM

A combined flow injection (FI)-capillary electrophoresis (CE) system w ith a split-flow interface reported previously was used for on-line pr econcentration of pseudoephedrine by solid phase extraction on a micro -column packed with C-18 Aqueous samples were loaded on the column at 1.0 mi min(-1) for 90 s and eluted by a mixed eluent of 40% 62.5 mM ac etate buffer (pH 4.0) and 60% acetonitrile at 0.2 mi min(-1). A zone-s ampling approach was employed to sample 45 mu l of the most concentrat ed zone of the eluate, which was injected into the FI-CE split-flow in terface using a phosphate buffer carrier, with a 25 mu l water zone pr eceding the sampled eluate zone to achieve enhanced field amplificatio n effects. Sensitivity enhancements of 60 fold (180 fold with 4 min sa mple loading) were thus achieved with a sample throughput of 9 h(-1) a nd 4.7% relative standard deviations (n = 10, 2 mu g ml(-1) pseudoephe drine) for peak area evaluation, without significant degradation of co lumn efficiency. (C) 1997 Elsevier Science B.V.