Dz. Liu et al., THEORY OF THE SURFACE-ACOUSTIC-WAVE IMPEDANCE SENSOR SYSTEM AND ITS APPLICATION TO THE END-POINT DETERMINATION IN TITRIMETRY, Analytica chimica acta, 320(2-3), 1996, pp. 245-254
Theory and characteristics of the surface acoustic wave (SAW)/impedanc
e sensor system in electrolyte solution are reported. This kind of sen
sor was constructed by a 62-MHz SAW resonator and a pair of conductive
electrodes in series. By using the circuit network analysis theory, t
wo oscillation equations were derived and used to explain the frequenc
y-shift response to solution conductance. Results showed that the sens
or possesses high sensitivity to the solution conductivity and can be
applied to conductivity measurements in solution. Its sensitivity and
accuracy could be improved in the presence of a large amount of unreac
ting foreign electrolytes. The sensor was successfully applied to four
types of titration (acid-base, precipitation, oxidation-reduction and
compleximetric titration) by monitoring the frequency-shift response.
Factors influencing the frequencimetric titration curve were also inv
estigated. Analytes at levels down to 1 X 10(-5) M could be determined
by the proposed titration technique. The total acidity in several foo
d samples was determined and the results were consistent with those ob
tained by conventional methods.