Determination of josamycin in rat plasma by capillary electrophoresis coupled with post-column electrochemiluminescence detection

A novel determination method for josamycin (JOS) based on capillary electrophoresis–electrochemiluminescence detection has been described. In this study, platinum disk electrode (300 μm in diameter) was used as a working electrode and the conditions affecting separation and detection were investigated in detail. Under optimal condition: 40 cm separation capillary (75 μm i.d.); 1.25 V applied potential on the Pt disc of the ECL detector cell; 5 mM Ru(bpy)32+ and 50 mM phosphate buffer (pH 7.5) in the detection cell; 12 kV separation voltage; 8 s injection time; 10 kV injection voltage and 15 mM running buffer (pH 7.5), calibration curve was linear over the range from 10 ng/mL to 5.0 μg/mL with a detection limit of 3.1 ng/mL at a signal-to-noise ratio of 3. The method can be successfully applied for the determination of josamycin in rat plasma in 6 min and the extraction recoveries with spiked plasma samples were over 92%.