Analytical applications of electrode sensors

Vita.Potentiometric titrimetry using calcium and chloride selective electrodes is investigated and a new conductimetric gas sensor is developed as an alternative to conventional potentiometric gas sensing electrodes. Complexometric titrations of calcium with several aminocarboxylic acid chelating ligands, and precipitation titrations of sodium chloride with silver nitrate are studied. The forms of the various titration curves resulting from titrations of these model chemical systems are developed via determination of selectivity coefficients and calculations using the Eisenman-Nicolsky and Nernst equations. Once the curve shapes are defined, several numerical methods which make use of cubic polynomials and spline functions are evaluated for precision in location of equivalence points in Ca-EDTA and AgCl titrations. Results show that the spline methods offer significant advantages in precision with some losses in accuracy. A new conductimetric gas sensor is also described and its response characteristics evaluated. It is shown that the conductance of the sensor is proportional to the square root of the sample carbon dioxide concentration for a range of P[Subscript)CO2 values from less than 1 mm Hg to greater than 100 mm of Hg. In preliminary investigations, the sensor is used to monitor carbon dioxide in titrations of small sample volumes of sodium carbonate with hydrochloric acid. The form of the resulting titration curves indicate that location of equivalence points is facilitated by use of this conductimetric method