LAUSR

OBJECTIVE This research describes the simultaneous quantitation of Paracetamol (PRM) and Lornoxicam (LRX) with five of their related substances and toxic impurities, including, 4-nitrophenol (NTP), 4-aminophenol (AMP), 4-chloroacetanilide (CAC), N-phenylacetamide (NPA), and 2-aminopyridine (APD) using a specific HPLC-DAD method. METHODS The chromatographic separation involves the use of XTerra C18 column as the stationary phase and a mobile phase consisting of acetonitrile and 0.025 M phosphate buffer (pH 6). The separation was performed using gradient elution mode at 1.0 mL min-1 flow rate and detection at 260 nm for the determination of PRM and LRX. While for detecting PRM, LRX in presence of their toxic impurities, 270 nm was convenient. Validation of the suggested HPLC method was accomplished in regards to linearity, ranges, detection and quantitation limits, robustness, accuracy, precision and specificity. RESULTS Excellent resolution of the mixture components was accomplished at retention times 4.2, 4.8, 7.4, 11.1, 13.5, 14.7 and 15.3 min for APD, AMP, PRM, NPA, LRX, NTP and CAC, respectively. Linearity was established for PRM and LRX within concentration ranges of 10-100 and 10-60 µg/mL, respectively. The correlation coefficients obtained were > 0.9997. The suggested method was confirmed to be a specific stability-indicating through the selective separation of PRM and LRX from their related substances, degradants and impurities. CONCLUSION The proposed method was successfully utilized for the sensitive and selective determination of PRM and LRX in their pharmaceutical formulation. HIGHLIGHTS To the best of our knowledge, this is the first impurity profiling assay method for this combination in presence of five of their toxic related substances and impurities. Taking into consideration that at least 2 of the studied impurities (AMP and APD) are actually reported degradation products for the main drugs, therefore the suggested method can be considered stability-indicating as well.