Fig 2 Effect of different mobile phase ratios on GABA response Chromatograms obtained with different mobile phase compositions. A: Mobile phase A1 (0.05% formic acid in water) and mobile phase B1 (90% acetonitrile in water) containing 5 mmol/L ammonium acetate; B: Mobile phase A1 (0.05% formic acid in water) and mobile phase B1 (90% acetonitrile in water) containing 0.10% formic acid and 5 mmol/L ammonium acetate; C: Mobile phase A1 (0.05% formic acid in water) and mobile phase B1 (90% acetonitrile in water) containing 0.175% formic acid and 5 mmol/L ammonium acetate.