2.2.1. LC-MS/MS

The Agilent series 1260 HPLC system was used for the analyses. The substances were separated on a Luna 3 μm Phenyl-Hexyl 150 mm × 2.0 mm column (Phenomenex, Torrance, NJ, USA) using water with 5 mM ammonium formate and acetonitrile as the mobile phase. The flow rate was 400 μL/min and the column was thermostated at 50 ◦C. Gradient elution was used. The injection volume was 2 μL, and the total LC analysis time was 40 min. Spectrometric analysis was performed using the AB Sciex QTRAP® 6500 LC-MS/MS system (Framingham, MA, USA) with the Turbo Spray ion drive with positive ionization and positive and negative ionization. The spray voltage was set to 5000 V and −4500 V for positive and negative ionization, respectively. The source temperature was set to 550 ◦C. Nitrogen was used as the curtain gas (20 psi), collision gas (medium), and ion source gases, nebulizer gas (50 psi) and heating gas (55 psi). Analyst 1.6.2 software (AB Sciex, Framingham, MA, USA) was used to control the LC-MS/MS system and to archive the data.
