Figure 7.

Optimization of (A) centrifugation speed, (B) centrifugation time and (C) pH. Extraction conditions: extraction solvent, chloroform (40 µl); disperser solvent, acetone (1 ml); sample volume, 10 ml; analyte concentration, 7 µg/ml of sodium valproate; concentration of NaCl, 4% (w/v); extraction time, ~0 min for A-C; (A) pH, 2.0; centrifugation time, 5 min; (B) pH, 2.0; centrifugation speed, 6000 rpm; (C) centrifugation speed, 6000 rpm; centrifugation time, 6 min. The bars indicate the standard deviations (n=3)