Quantification of aristolochic acids I and II in herbal dietary supplements by ultra-high-performance liquid chromatography-multistage fragmentation mass spectrometry

A rapid, selective and sensitive ultra-high-performance liquid chromatography-multistage fragmentation mass spectrometry (UHPLC-MS³) method was developed and evaluated for the determination of aristolochic acids I and II (AA I and II) in herbal dietary supplements. A hybrid triple quadrupole/linear ion-trap mass spectrometry was used to monitor MS³ ion transitions m/z 359.2 > 298.1 > 268.0 and m/z 329.2 > 268.2 > 238.0 to detect AA I and II, respectively. The extraction and clean-up of target analytes from dry powdered samples was performed using the quick, easy, cheap, effective, rugged and safe (QuEChERS) procedure. Herbal liquid extracts were analysed directly. Average recoveries ranged from 89% to 112%, with relative standard deviations (RSDs) ranging from 3% to 16%. Limits of quantification (LOQs) estimated for three selected matrices were as follows (AA I/II): 5/10 ng g⁻¹ (tablets); 25/50 ng g⁻¹ (capsules); and 2.5/5.0 ng ml⁻¹ (liquid herbal extract). The method was applied in a limited survey of 30 herbal products marketed in the United States via the Internet. AA I and II were detected in 20% and 7%, respectively, of tested samples.