pH Measurement of Mixed Saliva using a Flow-injection Sensor with a Tubular Carbon Electrode

Abstract

Present work discusses the design of a flow-injection sensor for measuring pH in micro-volumes of the sample. A carbon electrode with a capillary channel was used as a working electrode, through which an electrolyte solution saturated with quinhydrone flows at a constant speed. The volume of the analyzed sample was 0.1-0.2 mL. Compliance with the Nernst pH function with a slope of 53.1 ± 1.1 mV/pH was observed in the range of 1.0-7.5 pH. The sensor has been tested in the non-invasive diagnostics of acid-base balance of the oral fluid. The analysis of mixed saliva was carried out in 30 practically healthy student volunteers with an intact row of teeth. The median pH value of 7.03 was established, which corresponds to the physiological norm. At the same time, there is a predisposition to caries in almost half of the subjects, since a high risk is determined in the formation of focal demineralization of tooth enamel with the appearance of erosion of hard tooth tissues.