Detecting aristolochic acids in herbal remedies by liquid chromatography/serial mass spectrometry

Targeted liquid chromatography/serial mass spectrometry (LC/MS/MS) analysis, using a quadrupole ion-trap mass spectrometer, permitted the detection of aristolochic acids I and II in crude 70% methanol extracts of multi-component herbal remedies without any clean-up or concentration stages. The best ionisation characteristics were obtained using atmospheric pressure chemical ionisation (APCI) and by including ammonium ions in the mobile phase. Limits of detection for aristolochic acids were influenced by the level of interference created by other components in the sample matrix. They were determined to be between 250 pg and 2.5 ng on-column within a matrix containing compounds extracted from 2 mg of herbal remedy. With a herbal remedy that only permitted the higher limit of detection, this sensitivity was sufficient to detect the aristolochic acids extracted from 0.1% dry weight of Aristolochia manshuriensis included in the preparation.