Solid-phase Extraction of Valproic Acid Using a Surfaced Imprinted Silica Gel Adsorbent

Using a solid-phase extraction for the determination of VPA, this study aimed to prepare a vaiproic acid (VPA) imprinted silica gel adsorbent by surface molecular imprinting technique. VPA-imprinted silica adsorbent was characterized by FTIR spectroscopy. The VPA adsorption from solutions was studied in SPE mode. All influenced parameters on adsorption efficiency, including the elution concentration, MW amount, VPA concentration, pH and salting effect, sample flow rate, column performance repeatability (relative standard deviation) were optimized independently. The prepared adsorbent showed significant adsorption capacity and selectivity for VPA. In the condition of sodium hydroxide solution (0.1 M), MW polymer (250 mg), VPA (10(-4) M), sample flow rate (1 ml min(-1)), pH around 2-6 in the presence of 4 NaCl, total VPA retention showed better reproducibility than 5. Recovery of VPA was about 94.6 to 98.1 and the relative standard deviation was less than 5.69. These results demonstrated that the prepared adsorbent can be used to measure VPA in biological samples. GRAPHICS

Graphite Electrode Potentiometric Sensor Modified by Surface Imprinted Silica Gel to Measure Valproic Acid

The aim of the study was to produce a Polyvinyl chloride-based membrane containing a polymer imprinted with a valproic acid molecule which was directly coated on a graphite electrode to determine the amount of valproic acid in aqueous samples. With the dispersion of molecularly imprinted polymer particles in dioctyl phthalate plasticizer as a solvent mediator, this potentiometric sensor was designed and after that it was embedded in a polyvinyl chloride matrix. The designed electrode showed a near-Nernstian slope of 54.1 +/- 1 mV decade(-1) in the concentration range of 10(-6)-10(-2) M and a detection limit of 10(-6) M with a response time of about 40 seconds for valproic acid and can be used for 2 months without divergence changing the potential. The fabricated electrode, in the pH range among 3.5-8.5, indicates the good sensitivity to valproic acid relative to the other ions. Finally, this electrode can be used as an indicator electrode in determining the concentration of valproic acid in valproic acid tablets. GRAPHICS