column (20 m x 0.18 mm i.d. x 0.18 μm coating (Restek, Bad Homburg, Germany). In the second dimension after the QuadJet thermal modulator a more polar column (Rxi-17Silms, 0.45 m x 0.15 mm ID x 0.15 μm coating [...] containing 0.1% acetic acid (solvent A) and acetonitrile (solvent B). The elution started with 100 % A, decreasing from 1 to 9 min to 50 % A, followed by decreasing to 0 % during 0.5 min, after 1.5 min 0 % A [...] analyzed by Agilent 6890GC-5975MSD instruments. Agilent columns, Ultra 1 (25 m, 0.2 mm, 0.11 µm) and Ultra 2 (25 m, 0.2 mm, 0.33 µm) were employed. Injection volume 2 µL; split, SIM acquisition modes. Ultra