Evaluation of dispersive liquid-liquid microextraction in the stereoselective determination of cetirizine following the fungal biotransformation of hydroxyzine and analysis by capillary electrophoresis.

We developed a capillary electrophoresis (CE) and dispersive liquid-liquid microextraction (DLLME) method to stereoselectively analyze hydroxyzine (HZ) and cetirizine (CTZ) in liquid culture media. The CE analyses were performed on an uncoated fused-silica capillary; 50mmolL(-1) sodium borate buffer (pH 9.0) containing 0.8% (w/v) S-β-CD was used as the background electrolyte. The applied voltage and temperature were +6 kV and 15 °C, respectively, and the UV detector was set to 214 nm. Chloroform (300 µL) and ethanol (400 µL) were used as the extraction and disperser solvents, respectively, for the DLLME. Following the formation of a cloudy solution, the samples were subjected to vortex agitation at 2000 rpm for 30s and to centrifugation at 3000 rpm for 5 min. The recoveries ranged from 87.4 to 91.7%. The method was linear over a concentration range of 250-12,500 ng mL(-1) for each HZ enantiomer (r>0.998) and 125-6250 ng mL(-1) for each CTZ enantiomer (r>0.998). The limits of quantification were 125 and 250 ng mL(-1) for CTZ and HZ, respectively. Among the six fungi studied, three species were able to convert HZ to CTZ enantioselectively, particularly the fungus Cunninghamella elegans ATCC 10028B, which converted 19% of (S)-HZ to (S)-CTZ with 65% enantiomeric excess.