Determination of relative response factors of impurities in paclitaxel with high performance liquid chromatography equipped with ultraviolet and charged aerosol detectors

A case study was conducted to determine the relative response factors (RRFs) of paclitaxel-related impurities by high performance liquid chromatography (HPLC) equipped with an ultraviolet (UV) detector and charged aerosol detector (CAD) in tandem. The peak response using CAD was independent of analyte structure in an isocratic analysis for this application. After a sample containing known and unknown impurities was analyzed with HPLC–UV–CAD, an empirical approach was developed to calculate the RRFs for all impurities. The RRFs of known impurities were also determined by linear calibration curves. For known impurities, the RRFs values determined with two approaches are comparable. The new approach is effective yet simpler to determine the RRFs for unknown impurities or degradation products since the need for obtaining authentic pure materials was eliminated.