Stability-indicating UHPLC and TLC-densitometric Methods for the Determination of Tiamulin Fumarate

Two novel stability-indicating methods were developed for the determination of tiamulin fumarate. in the presence of its degradation products. The first was UHPLC-UV method. Efficient separation was achieved by isocratic elution with a mobile phase of 0.1% aqueous ortho-phosphoric acid (pH 3.5 ± 0.5) and methanol (20:80, v/v) with UV detection at 210 nm. Linearity was obtained in the range of 0.5-10.0 µg mL-1 with mean accuracy of 100.40 ± 0.71. The second method was a TLC-densitometric evaluation of a thin-layer chromatogram of the intact drug using a mobile phase of methanol: pentanol: ethyl acetate: 16.5% ammonia (5:4:2:4, by volume). The TLC-plates were scanned densitometrically at 220 nm where Rf values were 0.58, 0.48 and 0.74 for tiamulin F, its acidic and oxidative degradants, respectively. Moreover, the plates were sprayed with 16% sulfuric acid, heated at 105°C for 10 min. where a yellow-coloured band appeared corresponding to the intact drug was scanned densitometrically at 450 nm. While the bands of the two degradants were no longer observed anymore. Tiamulin F was determined in the range of 1.0-10.0 μg/band with mean accuracy of 100.27% ± 1.47 at 220 nm and 99.93% ± 1.38 at 450 nm. The proposed methods were successfully applied for the determination of drug in marketed oral solution. The obtained results were statistically analyzed and found to be in accordance with those obtained by a reported method.