The paper aimed to test suitable conditions for the determination of VPA in serum using the ITPCZE method with conductometric detection. It attempted to find whether for the method described by Ölvecká et al. it is possible to use a similar procedure of sample preparation as for the gas chromatographic method which is routinely employed for the assessment of VPA in serum. A 200 rl sample of serum was extracted with 200 rl of acetone and after centrifugation 200 rl of the upper layer was withdrawn and supplemented with demineralized water to make 10 ml. When a microsyringe is used for dosing, consumptions of serum can be reduced up to 5 rl, which is advantageous mainly for therapeutic drug monitoring in children. The length of analysis was 20 minutes. The method was linear within the range of 20–400 mg/l, which includes the therapeutic range of VPA (50–100 mg/l). The detection and quantification limits were 2.5 and 8.5 mg/l, respectively. The variation coefficients were below 10 % in all three concentrations (30, 70 and 120 mg/l). The new method was compared with the method of gas chromatography by means of the Passing-Bablok regression analysis and both methods were found to give identical results.

        Key words: electromigration methods – capillary zone electrophoresis – isotachophoresis –valproic acid – therapeutic drug monitoring