The following dissertation is a study of the properties of compact potentiometric sensors – pH meters (Hanna Instruments, Checker – pH tester HI98103) – and their possible usage as a substitute for a stationary laboratory pH meter. A series of experiments was carried out. Time needed for a pH meter to reach a steady response was determined using calibration buffers. Time stability of calibration was observed for a ten-day period with measurements of calibration buffers. The linearity of the pH meter response was tested with the use of buffers with pH 1 through 13. The occurrence of alkaline error was investigated with buffers with different pH and different sodium ion concentrations. The application of pH meter for titrations and the determination of end points was examined with various types of titration; a strong acid with a strong base, a weak acid with a strong base and a polyprotic acid with a strong base.
It was determined that the time needed for a pH meter to reach a steady response is dependent on the size of the difference of pH values and correspondingly lengthens with a larger difference in pH. The calibration of pH meter is sufficiently stable in the experimental time period and the measurement deviation does not exceed the value of the inherent error of the pH meter. The response of the pH meter is linear in the whole pH range (from pH 1 to pH 13). The alkaline error was observed at high pH values. Measured pH values at lower pH are very temperature dependent, as opposed to measured pH values at higher pH, where the variance is negligible. pH meter is applicable for all types of titration and the determination of the end point.
Compact pH meter (Hanna Instruments, Checker – pH tester HI98103) is a hand-held device, that can be simply operated and is thus appropriate for field work. In a laboratory environment the pH meter is usable for student laboratory practice, for direct potentiometry and potentiometric titrations and less accurate analyses.
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