Development of characterization methods for entacapone in a pharmaceutical bulk

A comprehensive approach was taken to develop analytical procedures for the characterization of entacapone in a pharmaceutical bulk. A novel reversed-phase HPLC method was developed and validated for the assay of entacapone and the determination of impurities. The method employed a C18 column, a mobile phase of potassium phosphate buffer (pH 2.75, 30 mM)-methanol (50:50, v/v) at a flow rate of 1.0 mL/min, and ultraviolet (UV) detection at 310 nm. The method was linear over the range from 50% to 150% of the assay concentration (0.2mg/mL). The limit of quantitation was 0.13 μg/mL, and the limit of detection was 0.05 μg/mL. Average recovery was 100.10% with a relative standard deviation (N=9) of 0.45%. Degradation studies showed that entacapone eluted as a spectrally pure peak and was well resolved from its degradation products. The method was specific, sensitive, precise, linear, and accurate. UV and infrared spectroscopy (IR) were suitable as identification tests. The UV and FTIR spectra were acquired from a candidate reference standard and two commercial bulks. All materials exhibited maxima and minima at the same wavelengths. Water sorption analysis showed that entacapone was not affected by atmospheric moisture. These methods can be used for qualitative and quantitative analysis of entacapone in a pharmaceutical bulk.