Semiquantitative estimation of enrofloxacin and ciprofloxacin by thin-layer chromatography - Direct bioautography

Fluoroquinolones, relatively new chemotherapeutics, are widely used in the treatment of both human and veterinary diseases because of their broad spectrum of antibacterial activity and good pharmacokinetic properties. Enrofloxacin is used in veterinary medicine, while its main metabolite, ciprofloxacin, is one of the most frequently used human antibiotics in the world. Hence, there is a need for assays capable of determining and distinguishing between these drugs. Thin-layer chromatography - bioautography (TLC-B) combines TLC with microbiological detection. In the present paper, semiquantitative determination of enrofloxacin and ciprofloxacin standards by TLC-B using Chrom Biodip(R) Antibiotics Test Kit is presented. The optimal conditions for bioautographic detection were established. The exponential relations were proposed for approximation of dependencies between areas of zone inhibitions and logarithm of the amounts applied. The detection limit for standards of both enrofloxacin and ciprofloxacin was 0.01 ppm, lower than maximum residue limits (MRLs) established for various food products.