PURITY CONTROL OF 6 TETRACYCLINES BY SEMIQUANTITATIVE TLC WITH FLUORESCENCE DETECTION

Thin layer chromatographic (TLC) methods are described for rapid and s imple control of the purity of chlortetracycline, demeclocycline, doxy cycline, metacycline, oxytetracycline, and tetracycline. The methods a re based on those previously developed for the identification and quan titative assay of tetracyclines. The stationary phase is silica gel, p reviously sprayed with 10% disodium EDTA solution adjusted to pH 8.0 o r 9.0. The mobile phase is dichloromethane - methanol - water water (5 9 + 35 + 6, v/v) or (60 + 35 + 5, v/v). After development the plates a re dipped in a 30% solution of liquid paraffin in hexane and inspected under UV light at 365 nm. The fluorescence is stable for long periods of time. The detection method is sensitive (< 0.05%) and the method i s suitable for rapid control of purity, e.g. in the pharmacy.