Development of a solid state ion sensor for the quantification of potassium ions in soil

Sciences and Techniques of Engineering and Innovation

This paper shows an investigation and development of a solid structure ion sensor for the quantification of potassium ions in soil. In this way, a review of the literature and the various researches which have been carried out in this field was carried out to constitute the constituent elements of the sensor. Following this research, a sandwich-type solid structure sensor was developed with the following different characteristics: - A ceramic insulating body 6 cm long with a bulbous end of 0.5 cm containing the conductive film and the polymer membrane selective for potassium ions - A PVC polymer with a dioctyl phthalate (DOP) plasticizer is added to the potassium ion-selective ionophore which is valinomycin. - A conductive layer composed of polypryrole serves as a conductive film between the selective polymer membrane and the metal substrate which is connected directly to the measuring voltmeter. A measurement to calibrate the sensor is then carried out with the potentiometer method and by associating the working electrode with a reference electrode saturated with calomel. The sensor has been calibrated in a wide range of potassium concentrations between 10-6 and 1mole of KCl. The result obtained from this measurement is a curve of 36.5 mv/decade which does not conform to the expected result of 59 mv/decade of concentration. After several researches, it was found that: - Sensor conditioning was omitted before the first measurement. - The electrode should be conditioned in a 0.1 mole of KCl solution for at least 24 hours. For the remainder of this study, it is necessary to study in detail the influence of conditioning on solid configuration membrane electrodes.

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