APCI source parameters were: vaporizer temperature = 400°C; sheath gas flow = 32 arbitrary units, auxiliary sheath gas flow = 5 arbitrary units; discharge current = 4 μA; capillary temperature = 250°C, capillary voltage = 30 V, tube lens = 70 V.
The tube lens was optimized to be 140 V. Nitrogen was used as sheath gas (60 units), auxiliary gas (5 units) and sweep gas (3 units).
Conditions for analysis in positive ion mode were: spray voltage at 5.0 KV, sheath gas flow rate at 50 arbitrary units, auxiliary gas flow rate at 3.0 arbitrary units, capillary temperature at 275°C, and capillary voltage at 10 V. Spectra were scanned over a mass range of m/z 180 2000 at 3 scans sec−1.
Gas settings were sheath gas pressure, 40 (arbitrary units); auxiliary gas pressure, 35 (arbitrary units); ion sweep gas pressure, 0 (arbitrary units).
The electrospray source was operated in positive mode using the following parameters: electrospray voltage, 2.8 kV; sheath gas, 19 arbitrary units; auxiliary gas, 7 arbitrary units.
The MS settings were capillary temperature 350°C, ion spray voltage 4 kV, sheath gas flow 60 (arbitrary units), auxiliary gas flow 10 (arbitrary units), sweep gas flow 5 (arbitrary units).
The ESI interface was used in positive ion mode with the following settings: sheath gas, 60 arbitrary units; auxiliary gas, 15 arbitrary units; sweep gas, 5 arbitrary units; capillary voltage, 4 kV; capillary temperature, 300 °C.
Peptides were quantified using SRM in positive ion mode under the following conditions: ionization voltage, 3500 V; sheath gas pressure, 10 arbitrary units; auxiliary gas pressure, 1 arbitrary units; capillary temperature, 270°C; Tube lens offset, 92; Collision pressure, 1.5.
Detection was by ultraviolet (full spectra from 200-600 nm) and by positive electrospray MS using spray chamber conditions of 350°C capillary temperature, 50 units sheath gas, five units auxiliary gas, and 5.2 kV spray voltage.
The MS was operated at a positive electrospray mode with the following settings: capillary temperature, 325 °C; spray voltage, 5 kV; sheath gas flow, 60 (arbitrary units); auxiliary gas, 20 (arbitrary units).
The MS operating conditions were optimized and set as follows: sheath gas pressure, 30 arbitrary units; auxiliary gas pressure, 10 arbitrary units; capillary temperature, 350 °C; spray voltage, 3800 V and source collision-induces dissociation (CID), 15 V.
