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Assay and purity control of metacycline by thin-layer chromatography combined with UV and fluorescence
1Katholieke Universiteit Leuven, Laboratorium voor Farmaceutische Chemie, Leuven, Belgium.
Abstract:
A thin-layer chromatographic (TLC) method involving UV and fluorescence densitometry is described for the assay and purity control of metacycline. With a mobile phase dichloromethane-methanol-water (58:35:7, v/v/v) and a silica gel thin-layer, previously sprayed with 10% sodium edetate solution adjusted to pH 9.0, all the potential impurities of metacycline were well separated from the main component and from each other. Results obtained with UV densitometry (TLC-UV) and fluorescence densitometry (TLC-F) were compared with those obtained by a liquid chromatography (LC) method using a poly(styrene-divinylbenzene) stationary phase. The correlation coefficients (r) for TLC-UV and LC or TLC-F and LC were better than 0.9999. For TLC-UV the relative standard deviation (RSD) for the assay of the main component was less than 2%, for TLC-F less than 3.0% and for LC less than 1.0%.