A sensitivity enhanced high-performance liquid chromatography fluorescence method for the detection of nephrotoxic and carcinogenic aristolochic acid in herbal medicines

A new, sensitive and selective HPLC method with fluorescence detector (HPLC–FLD) for the determination of nephrotoxic and carcinogenic aristolochic acid (AA) in herbal medicines by using pre-column derivatization with zinc powder in acetic acid is presented. Variables governing the derivatization reaction, such as the amount of zinc powder and acetic acid, as well as the derivatization time were studied and optimized. An extended linear dynamic range over three orders of magnitude was observed for AA-I and AA-II (R2 > 0.9998). Method accuracy at low, medium and high spiked AA levels determined by the percentage mean deviation was below 4.4% and 7.2% for AA-I and AA-II, respectively. The detection limits of 0.39 ng/mL (AA-I) and 0.52 ng/mL (AA-II) were 2 orders of magnitude lower than those obtained from HPLC-MS or CE-ECD analyses, 3–4 orders of magnitude lower than those from HPLC-UV or CE-UV methods. The developed method has been applied for the determination of AA in herbal medicines. Among the tested samples, Guanmutong had the highest AA concentration (2607.0 μg/g AA-I, 711.2 μg/g AA-II). Comparison studies between HPLC–FLD and HPLC–MS/MS demonstrated that the two methods gave similar quantitative results for the selected herb samples.