Fig. 3

Extracted ion chromatograms of three different hydrophilic compounds at 50 ng/mL depending on the injection solvent composition for a RPLC separation (10 µL injection volume into 300 µL/min water:methanol 95:5 both with 0.1% formic acid at gradient start, on a Phenomenex Kinetex C₁₈ EVO, 50 × 2.1 mm, 2.6 µm particle size; column dead time is 0.5 min)