Fig. 2.

CE-TOF-MS of heat-exposed oxytocin solutions of a pH 2.0, b pH 4.5, c pH 7.0, and d pH 9.0 using a PB-DS-PB coated capillary. EIEs are at indicated m/z values (±0.01 Da). Conditions: BGE, 525 mM acetic acid (pH 3.0); sheath liquid, isopropanol–water–acetic acid (75/25/0.1, v/v/v) at 2 μL/min. Sample preparation and other conditions, see Materials and methods section