Kinetics Study of Moprolol Degradation under Various Stress Conditions Using Stability Indicating Assay by RP-HPLC Method

ABSTRACT

This study describes the development and validation of stability indicating HPLC method for moprolol, an antihypertensive drug. The drug was subjected to stress degradation under different conditions recommended by International Conference on Harmonization. The sample so generated was used to develop a stability-indicating high performance liquid chromatographic method for moprolol. The peak for was well resolved from peaks of degradation products, phenomenex C18 column (250 mm ×4.6 mm, 5 μ) at 37⁰C, using an isocratic mobile phase consisting of mixture of 10 mM potassium dihydrogen phosphate buffer with 0.1% V/V TEA in Milli-Q water (pH 3, adjusted with OPA): ACN: Methanol (50:40:10 %V/V/V) at a flow rate of 1 mL minute^-1. The retention times were found to be 3.3 min, respectively. Detection was carried out using photodiode array detector. A linear response (r > 0.99) was observed in the range of 0-40μg/mL. The method was found to be specific and stability-indicating as no interfering peaks of degradants and excipients were observed. The method showed good recoveries (average 99.5%) and relative standard deviation for intra and inter-day were ≤ 2 %. The method was validated for specificity and robustness also.The proposed method is hence suitable for application of degradation kinetics of moprolol under different stress conditions employed. Degradation followed a pseudo-first-order kinetics, and rate constant (k), time left for 50% potency (t_1/2) and time left for 90% potency (t₉₀) were calculated. This method can also be applied in quality-control laboratories for quantitative analysis of both the drugs individually and in combination, since it is simple and rapid with good accuracy and precision.

Keywords: Moprolol, reversed-phase HPLC, stability-indicating assay, forced degradation studies, method validation, kinetics