POTENTIOMETRIC SENSOR FOR THE DETERMINATION OF FENOPROFEN

Abstract

The development of applied potentiometry requires both theoretical studies devoted to the elucidation of the nature of the selectivity of electrode membranes, and the search for new methods of membrane synthesis and its modification in order to obtain more perfect structural units with a wider range of functional properties of these materials. In order to solve this problem, an important role is played by establishing a connection between the structural characteristics of the membranes and their influence on the electroanalytical properties. The interaction of the organic anion of fenoprofen (Fen- ) with toluidine blue (TB+) was investigated. The energy efficiency of the formation of IA was substantiated by the method of mathematical modeling. Molecular modeling of Fen- + TB+ systems and related calculations were carried out using the HyperChem 8.0 package for various initial options for the arrangement of counterions relative to each other ("single point" procedure). Geometrical optimization of ions was carried out using the MM+ molecular mechanics method. A fenoprofen-selective sensor with a plasticized polyvinyl chloride membrane was developed. The electrode contains an ionic associate of fenoprofen with toluidine blue. To model the composition of the membrane, PVC was used as a matrix; investigated membranes plasticized with dibutyl phthalate (DBF), diethyl phthalate (DEF), dioctyl phthalate (DOF), dinonyl phthalate (DNF), dibutyl sebaceate (DBS), tricresyl phosphate (TCF). It was established that the nature of the plasticizer somewhat affects the steepness and to some extent the detection limit of the sensors. The response is linear within the range of fenoprofen ion concentration change of 8·10–5 – 1·10–1 mol/l with a slope of the electrode function of 40.0 ± 1.0 mV/РС. The sensor has a short response time of 5-10 s and can be used for at least 10 weeks. Sensors with a higher content of plasticizer work longer than with a lower content. The electrode can be used in the pH range of 6.5-12.0. Selectivity coefficients for fenoprofen with respect to potentially interfering ions were investigated. To evaluate the developed sensors, their approbation was carried out for the determination of fenoprofen in various objects by the potentiometry method.