MEMBRANE POTENTIOMETRIC SENSOR FOR ETONIUM DETERMINATION

This work is devoted to the development methods for quantitative determination etonium in the substance and in the sample of cosmetic products by direct potentiometry using a membrane potentiometric sensors sensitive to the concentration of etonium. It was established that as a result of the interaction between organic cation of etonium and 12-molybdophosphate acid a low-soluble compound of composition (Et)3(РМо12О40)2 is formed. This compound was used as an electroactive substance for synthesis of a film polyvinylchloride membrane of a potentiometric sensor. The developed sensor was examined on the influence of various factors on its electrode characteristics: the nature of the solvent-plasticizer of the membrane, the nature of the electroactive substance, the quantitative content of the electroactive substance in the membrane, the pH of the investigated solution. The response time of the sensor is 60–240 s depending on the concentration of the test solution. The lifetime of the membrane (50 days) allows to measure the etonium concentrations without replacement of electrode. The developed techniques provide sufficient sensitivity, accuracy and selectivity for determination.