Figure 4.
Effect of extraction solvent volume on the microextraction efficiency. Extraction conditions: extraction solvent, chloroform; disperser solvent, acetone (1 ml); sample volume, 5 ml; analyte concentration, 7 µg/ml of sodium valproate; pH, 2.0; concentration of NaCl, 4% (w/v); extraction time, ~0 min; centrifugation time, 5 min and centrifugation speed, 6000 rpm. The bars indicate the standard deviations (n=3)