A stability-indicating HPLC method has been developed and validated for simultaneous estimation chlorzoxazone, diclofenac potassium and paracetamo in bulk drug and pharmaceutical dosage forms. Stress studies were conducted for all three drugs under ICH prescribed stress conditions viz. hydrolysis, oxidation, thermal and neutral stress. An isocratic RP-HPLC method was achieved on younglin HPLC system using Varian C18 (250x4.6 mm i.d, 5 μm particle size) column for separation of drug from its degradation products using mobile phase containing mixture of methanol: phosphate buffer (pH 3.0, adjusted with glacial acetic acid) (70:30, v/v). The flow rate was 0.8ml/min and the eluent was monitored at 280nm. Linearity was found in the range of 5-25μg/ml for diclofenac potassium (DIC), 25-125μg/ml for chlorzoxazone (CHL) and 32.5-182.5μg/ml for paracetamol (PCM). The limit of detection for DIC, CHL & PCM was found to be 0.15μg/ml, 1.82μg/ml and 2.40μg/ml respectively, while limit of quantification was 0.47μg/ml, 5.53μg/ml and 7.29μg/ml respectively. The developed method was found to be fast, accurate, precise, reproducible and suitable for analysis of all three drugs in bulk and pharmaceutical dosage forms.
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