LC-ESI mass spectra of anabaenopeptin (panel a) and anabaenopeptin B (panel b)

The externally calibrated spectra (no internal lock mass correction) were acquired with a sampling cone setting at 30 V. The data were acquired by using a Synapt G2 quadrupole/time-of-flight (Q-TOF) tandem mass spectrometer (Waters Co., Manchester, UK) equipped with an Acquity UPLC system (Waters) and an ESI source. Samples were injected into a reversed-phase column (ACQUITY UPLC BEH C18 1.7 µm, 2.1×50 mm, at 25°C) and eluted with an isocratic solvent system (solvent A: 0.1% formic acid in water; Solvent B: acetonitrile) at a flow rate of 0.2 mL/min for short gradient (30% B to 70% B in 1 to 2 min) LC-MS runs. The ions generated at positive ESI capillary (2.5 kV) under atmospheric pressure went into the vacuum system through the sampling cone (30 V). The ions went through the transfer optics were mass analyzed at the orthogonal TOF analyzer for the recording of a high-resolution (approx. 10,000 FWHM) externally calibrated product ion spectrum in each second. In post-run data processing, a few spectra at the retention time of each analyte were combined and converted to a centroid spectrum.