POTENTIOMETRIC SENSOR FOR THE DETERMINATION OF NAPHAZOLIN

Abstract

The development of applied ionometry at this stage requires both theoretical research, invested in elucidating 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. functional properties of these materials. 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 cation naphazoline (NAF+) with methyl orange (MO-) was studied. Using the method of mathematical modeling, the energy efficiency of the formation of the IA is substantiated. Molecular modeling of MO– + NAF+ 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 naphazolineselective sensor with a plasticized polyvinyl chloride membrane was developed. The electrode contains an ionic associate of naphazolium with methyl orange. 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 sebacenate (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 changes in the NAF ion concentration of 1·10–5–1·10–1 mol/l with a slope of the electrode function of 53.1 ± 1.0 mV/pС. The sensor has a fast response time of 10 s and can be used for at least 8 weeks without any deviations in the long term. Sensors with a higher content of plasticizer work longer than with a lower content. The electrode can be used in the pH range of 4.0–10.0. Selectivity coefficients for naphazoline with respect to potentially interfering ions were investigated. To evaluate the developed sensors, they were tested against naphazoline in model solutions and dosage forms. This sensor was used as an indicator electrode in the potentiometric determination of naphazoline in medicinal forms.