Capillary electrophoretic behaviour and determination of enoxacin in pharmaceutical preparations and human serum

A validated capillary electrophoretic method with UV detection is described for the determination of enoxacin [ENX] in pharmaceutical preparation and human serum. The experiments were carried out in a fused-silica capillary ( ID=75 tm, total 88 cm, effective 58 cm length) using a 20 mM borate buffer at pH 8.6, applying a potential of 30 kV, l s of injection. Acetylpipedimic acid was used as an internal standard (IS) and the detection was performed at 265 nm. The t(M)+/- RSD% of ENX and IS were 4.8 +/-0.9 and 5.5 +/-1.2 m inutes, respectively. A well-correlated calibration equation was obtained i n the range of 3.1x10(-6)-3.1x10(5) M ENX. Limit of detection (LOD) was 3.5 x10(-6) M (S/N = 3). A modified reversed-phase HPLC was also conducted using a C-18 ODS column f or the analysis of ENX to compare to its applicability with the CE method. An isocratic elution was performed using a mobile phase of 10 mM phosphate buffer (pH 4.0) and acetonitrile (85:15;v/v) detecting at 260 nm. The determination of ENX in the pharmaceutical tablet formulation was carri ed out by both methods and the results of a single tablet (as mg with their RSD% values) was found to be 421.4 +/-1.0 and 415.9 +/-0.9 by CE and HPLC, respectively. ENX analysis was also performed by a standard addition metho d in serum, and the recoveries were found to be 89.7 +/-0.6 (CE) and 78.8 /-4.9 (HPLC). It was concluded that capillary electrophoresis for the deter mination of ENX is a promising method for routine analysis and pharmacokine tic and bioavailability studies.