Table 2.

Agilent 7000A MS Parameters.

Helium Quench Gas (mL/min)	2.25
Nitrogen Collision Gas (mL/min)	1.5
Isobutane Reagent Gas (mL/min)	2
Ion Source Temp (°C)	350
Quad 1 Temperature (°C)	150
Quad 3 Temperature (°C)	150
Ion Source	Chemical Ionization (CI)
Mode	Positive Ion (PCI)
Electron Energy Mode	Use tune settings
Solvent Delay (min)	1.0
Run Time (min)	6.0
Time Filter Enabled
Peak Width	0.7
MS1 Resolution	Unit
MS2 Resolution	Unit
Dwell Time (msec)	50
Scan Rate (cycles/sec)	5
Collision Energy-GA (V)	15
Collision Energy-GABA (V)	20
Electron Multiplier (V)	1600
Delta EMV (V)	400
HED (kV)	−10
Instrument Tuning (Mass Calibration)
Tune MS weekly or as necessary
MRM Transitions
GA derivative (precursor ion/product ion)	m/z 204/144
d5-GA derivative (precursor ion/product ion)	m/z 209/148
GABA derivative (precursor ion/product ion)	m/z 146/101
D4-GABA derivative (precursor ion/product ion)	m/z 150/105