A Novel Optode for Vanadium Speciation: Sol–Gel Based Optical Sensor for Vanadium Determination

A highly selective optical sensor for V(IV) ions was established depended on entrapment of a sensitive reagent, ۵-(۲`,۴`-dimethylphenylazo)-۶-hydroxy-pyrimidine-۲,۴-dione (DMPAHPD), in a silica sol–gel thin film coated on a glass substrate. The thin films fabricated depended on tetraethoxysilane (TEOS) as precursor, sol–gel of pH = ۲.۵, water: alkoxyde ratio of ۴: ۱ and DMPAHPD concentration of ۲.۵ × ۱۰−۴ M. The effect of sol–gel parameters on sensing behavior of the fabricated sensor was also illustrated. The fabricated sensor can be used to detect V(IV) ion with an outstanding high selectivity over a wider dynamic range of ۵.۰–۱۴۵ ng mL−۱ and a detection limit of ۱.۳۵ ng mL−۱. It also recorded reproducible results with relative standard deviation of ۱.۷۵% and ۱.۰۲% for ۲۰ and ۷۰ ng mL−۱ of V(IV), respectively, along with a fast response time of two min. Total vanadium was determined after reduction of V(V) to V(IV) using ascorbic acid as reducing agent. The V(V) amounts were estimated by subtracting the concentration of V(IV) from the total vanadium concentration. Interference studies reported a good selectivity for V(IV) with trapping DMPAHPD into sol–gel matrix and appropriately adjusting the structure of doped sol–gel. The proposed sensor was compared with others and was applied to define vanadium in different environmental samples with good results.

کلیدواژه ها:

Optical Sensor Membrane ، Vanadium Determination ، Spectrophotometry ، Environmental Analysis