Quantification of Isoxicam in the Presence of Related Compounds by TLC-Densitometry.

A simple, sensitive, selective and precise TLC-densitometric determination of isoxicam as a drug was developed and validated. The method employed TLC aluminium plates precoated with silica gel 60 F254 as a stationary phase. The mobile phase consisted of ethyl acetate : toluene : butylamine (2:2:1, v/v/v). The system was found to give good resolution for isoxicam (RF value of 0.56). Densitometric detection was carried out at λ = 350 nm. The calibration plots showed good linear relationship in the working concentration range of 0.7 to 2.2 µg per band. The method was validated for precision (RSD < 1%), specificity, limit of detection and quantitation (0.22 and 0.67 µg per band, respectively). The drug was subjected to acidic and basic hydrolysis at different temperatures. All the peaks of the degradation products were well-resolved from the isoxicam with significantly different RF values. The products formed were identified by their TLC retention times (RF values), absorption spectra and HPLC-MS/MS analysis. The developed TLC-densitometric method can be applied for identification and quantitation of isoxicam in drugs, and it can be using as a screening method in pharmaceutical research. As the TLC method can effectively separate the drug from its degradation products it can be employed as a stability-indicating one and can be utilized to investigate the kinetics of degradation process.