Simultaneous targeted analysis of five active compounds in licorice by ultra-fast liquid chromatography coupled to hybrid linear-ion trap tandem mass spectrometry

An ultra-fast liquid chromatography with electrospray ionization tandem mass spectrometry (UFLC-ESI-MS/MS) method was developed for targeted analysis of 5 active compounds in licorice for the first time. The sample preparation procedure, chromatographic and mass spectrographic conditions were optimized. By using a Kinetex C18 100A column, the five compounds were separated within 8.0 min by gradient elution using methanol containing 0.1% acetic acid and 0.1% aqueous acetic acid. The precursor and product ions of the analytes were monitored on a hybrid quadrupole/linear ion trap mass spectrometer equipped with a turbo ion spray interface in negative ionization mode (ESI(-)) and were simultaneously characterized and quantified based on the multiple reaction monitoring-information-dependent acquisition-enhanced product ion (MRM-IDA-EPI) mode. All standard calibration curves expressed satisfactory linearity (r ≥ 0.9954) within a relatively wide range. The precision was evaluated by intra- and inter-day tests, which revealed relative standard deviation (RSD) values within the ranges of 1.15-4.56% and 0.81-3.95%, respectively. The recovery assays for the quantified compounds were between 97.33 and 100.4% with RSD values less than 4.27%. The proposed method was demonstrated to be simple, rapid, specific and reliable and was successfully applied for identification and quantification of 5 active compounds in 10 batches of licorice. The results showed that the contents of the 5 compounds in licorice from different sources were widely varied.