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.