Stability indicating thin-layer chromatographic determination of chlorzoxazone, diclofenac sodium and paracetamol as bulk drug: Application to forced degradation study

A simple, sensitive and precise thin-layer chromatographic method for determination of chlorzoxazone, diclofenac sodium and paracetamol both as bulk drug and in formulations was developed and validated. The separation was achieved on silica gel 60F-254 thin-layer chromatographic (TLC) plate as the stationary phase and the mobile phase consisted of toluene-ethyl acetate-glacial acetic acid (6.5:3.5:0.02 v/v/v). The solvent system was found to give compact spot for chlorzoxazone (R_f values of 0.23 ± 0.021), diclofenac sodium (R_f values of 0.51 ± 0.035) and paracetamol (R_f values of 0.64 ± 0.028). Densitometric analysis was carried out in the absorbance mode at 274 nm. The linear regression analysis data for the calibration plots showed good linear relationship with respect to peak area in the concentration range 200–800 ng spot^-1 of chlorzoxazone (with r = 0.9974), 40–160 ng spot^-1 of diclofenac sodium (with r = 0.9914) and 260–1040 ng spot^-1 of paracetamol (with r = 0.9965). The method was validated for limit of detection, limit of quantitation, accuracy, precision, robustness and recovery. Chlorzoxazone, diclofenac sodium and paracetamol were subjected to acid and alkali hydrolysis, oxidative, heat treatment and photodegradation. The drug undergoes degradation under acidic and oxidative conditions and upon UV light treatment. The degraded products were well separated from the pure drugs. The result and statistical analysis proves that the developed method is reproducible and selective for the estimation of said drugs. As the method could effectively separate the drugs from its degradation product, it can be employed as stability indicating one.

Author(s): Mrudula B. Kulkarni, Pratibha B. Dange and Sanjay G. Walode

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