Development of a potentiometric sensor sensitive to polysorbate 20

Abstract

Polyoxyethylated sorbitans (polysorbates) are widely used in the chemical, pharmaceutical, and cosmetic industries, but only quantitative determination is used mainly for chromatographic methods. In this paper, the results of the development and testing of a potentiometric sensor sensitive to nonionic surfactant polyoxyethylene sorbitan monolaurate (polysorbate-20) are presented. An anion of the heterogeneous acid of the Keggin structure (12-molybdophosphate heteropolyacid) was used as a counterion to obtain the electrode-active substance for the potentiometric sensor membrane. Polysorbate-20 does not form cations when dissociating in water and cannot directly interact with heteropolyanion; therefore, a cationic complex of polysorbate-20 with barium ions was previously prepared (similar to the interaction of metals with crown ethers). The resulting ion associate meets the basic requirement for the electrode-active substance of plasticized film polyvinyl chloride membranes of potentiometric sensors (poor water solubility and good solubility in organic solvents). Phthalic acid derivatives (dibutyl phthalate and dioctyl phthalate) were used as solvent-plasticizers for a polyvinyl chloride membrane. To determine the optimum conditions for the functioning of a potentiometric sensor sensitive to polysorbate-20, the influence of various factors on the electrode characteristics was studied. Quantitative content of the ionic associate in the polyvinyl chloride membrane, the nature of the membrane solvent-plasticizer, pH of a series of standard polysorbate-20 solutions) on the electrode characteristics of the plasticized membrane of the potentiometric sensor (sensitivity or slope of the electrode function, lower limit of linearity and minimum detectable concentration of polysorbate-20, which can be determined with the help of the developed potentiometric sensor) was studied. The optimal conditions for using the developed potentiometric sensor were found. The developed sensor allows for a short period of time (5–10 min) determining the quantitative content of polysorbate-20 in industrial products at the level 10–5–10 6 mol/l. The potentiometric sensor sensitive to polysorbate-20 can be used for the development of a potentiometric method for determining the clinical reception of polysorbate-20 in various types of industrial products.