A new fluorimetric method for determination of valproic acid using TGA-capped CdTe quantum dots as proton sensor

Valproic acid (VA) is an acidic anticonvulsant and mood stabilizing drug with very weak fluorescence and absorption properties. A simple, inexpensive and sensitive method was established for determination of VA using thiogycolic acid (TGA)-capped CdTe quantum dots (QDs) based on pH-dependent fluorescence of the prepared QDs. The TGA-capped CdTe QDs of various sizes were successfully synthesized in aqueous medium and characterized by fluorescence spectroscopy, UV-vis absorption spectra, infrared spectroscopy and transmission electron microscopy (TEM). Under the optimal conditions, plotting ln(F0/F) versus concentration of VA showed a linear relationship in the range of 0.3-7.5 mg/L with correlation coefficient of 0.998. The limit of detection (LOD) was 0.24 µg mL−1. The proposed method was successfully applied for determination of VA in commercial tablets, human serum, and urine samples satisfactorily.