TLC-Densitometric Determination of Tenoxicam and Its Degradation Products in Pharmaceutical Preparations and after Hydrolysis in Solutions

A direct, rapid, and sensitive thin-layer chromatography (TLC) method with densitometric detection was developed and validated for the determination of tenoxicam and its degradation products. The chromatographic separation was executed on silica gel TLC 60 F254 plates. Elution was performed with ethyl acetate-toluene-butylamine (2:2:1, v/v/v) as mobile phase. Quantitative analysis was carried out on the basis of the peak areas obtained from reflectance scanning densitometry performed at 288 nm. The method was validated in terms of linearity (35–1820 mg mL−1), accuracy (RSD < 1%), precision (RSD < 2%), sensitivity (LOD = 0.86 mg per band; LOQ = 2.30 mg per band), selectivity, and repeatability. Degradation products were identified by the RF values, absorption spectra, and LC-MS analysis. As the method could effectively separate the drug from its degradation products (i.e., pyridine-2-amine, tiophen), it can be employed as a method to indicate the stability of the compound. Moreover, the proposed TLC method was used to investigate the kinetics of the degradation process.