CAPILLARY ELECTROCHROMATOGRAPHY OF STEROIDS - INCREASED SENSITIVITY BY ONLINE CONCENTRATION AND COMPARISON WITH HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

A reversed-phase HPLC method previously developed for the analysis of progesterone and its major metabolites has been transferred successful ly to a capillary electrochromatography (CEC) system. Procedures for f abricating packed capillaries and the modifications made to the capill ary electropherograph which allow operation in the CEC mode without pr essurisation are described. The dependence of electroosmotic flow on e lectric field strength, pH and organic modifier content is discussed. Direct comparison with HPLC shows that CEC provides useful gains in ef ficiency and speed of analysis and requires vastly reduced amounts of both chromatographic phases and material for analysis. On-line concent ration is described which allows the lower sensitivity of CEC to be of fset by injecting analytes from a non-eluting solution. Examination of steroids in plasma demonstrates that the superior separation by CEC i s maintained in a complex biological matrix. (C) 1998 Elsevier Science B.V.