HPLC method for the determination of emtricitabine and related degradation substances

A new high-performance liquid chromatography method has been developed for a stability-indicating assay for emtricitabine and the quantification of its related substances. Good resolution between the peaks corresponds to process-related impurities, and degradation products from the analyte were achieved on a C18 HiQSil column using a mobile phase consisting of ammonium formate (pH 4.2) and methanol in a gradient elution mode. The detection was conducted at a wavelength of 280 nm. The investigated validation elements showed that the method has acceptable specificity, accuracy, linearity, precision, robustness and sensitivity. Detection and quantification limits were established at 0.02 and 0.05 µg/mL, respectively. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal decomposition to determine the degradation behavior. Extensive degradation was found under acid, alkaline and oxidative stress. Five related substances were consistently monitored under stress conditions. Because the method effectively separates the drug from its degradation products, it can be used as a stability indicating method and for purity control of emtricitabine.