Synapt g2s quadrupole ion mobility separation time of flight q ims tof mass spectrometer

ESI-MS measurements were carried out in either positive or negative ion mode using a Synapt G2S quadrupole-ion mobility separation-time of flight (Q-IMS-TOF) mass spectrometer (Waters, Manchester, UK) equipped with a nanoflow ESI (nanoESI) source. Each sample solution was prepared in 500 mM aqueous ammonium acetate buffer (pH 6.8, 25°C) and loaded into a nanoESI tip, which was produced from a borosilicate capillary (1.0 mm o.d., 0.68 mm i.d.) pulled to ~5 μm using a P-1000 micropipette puller (Sutter Instruments, Novato, CA). To perform ESI, a platinum wire was inserted into the nanoESI tip and a voltage of +1.1 kV (positive ion mode) or −0.9 kV (negative ion mode) was applied. A source temperature of 60 °C was used. The Cone, Trap and Transfer voltages were 100 V, 5 V and 2 V, respectively, and the Trap gas flow rate was 6.0 mL· min⁻¹; all other parameters were set at their default values. Data acquisition and processing were performed using Waters MassLynx software (version 4.1).