Online extraction and cleanup-quadrupole time-of-flight tandem mass spectrometry for rapid analysis of bioactive components in natural products.

The challenges in direct analysis of a complex system (e.g., natural product, food, biological samples) by mass spectrometry (MS) are the sophisticated sample preparation methods and ionization suppression by matrix interferences. Consequently, a novel online extraction and cleanup-quadrupole time-of-flight tandem mass spectrometry (OLEC-QTOF-MS/MS) system was developed for rapid, efficient, and sensitive analysis of flavonoids in Citri Reticulatae Pericarpium (CRP). For the OLEC strategy, a guard column packed with solid CRP (0.5 mg) and C18 gel was positioned on a manual injection valve, in which interferences with large polarities were online removed by methanol-0.1% formic acid (25:75, v/v) for 3 min, while target flavonoids were online extracted by methanol-0.1% formic acid (70:30, v/v) for 10 min for the subsequent QTOF-MS/MS analysis. The method was validated using official marker, hesperidin, by external standard method. Excellent linear ranges from 0.02 to 52.0 μg L-1 (R2, 0.9935) with a limit of detection (LOD) of 0.006 μg were obtained. Acceptable reproducibility (RSD 8.1 and 9.6% for intra- and inter-day variations) and recoveries (from 99.5 to 112.0%) were also attained. In addition, 20 flavonoids in CRP were identified according to their exact mass and fragmentation ions in MS/MS spectra, and five of them were reported for the first time. Obviously, OLEC-QTOF-MS/MS presented several advantages, such as simple operation and high sensitivity, which provided new perspectives for rapid analysis of bioactive components in complex natural products. Graphical Abstract ᅟ.