Maximum separation-distance for a separated-electrode piezoelectric sensor: application to the determination of cationic surfactant adsorbed onto quartz surface

In a separated-electrode piezoelectric sensor (SEPS), the two excitation electrodes are separated by solution layers. The oscillation ability of the SEPS depends obviously on the separation-distance between the two excitation electrodes. In a given solution, there is a maximum separation-distance (D-max) for the SEPS. If the separation-distance is > D-max, operation of the SEPS is not stable or even ceases to oscillate. The dependence of D-max value on conductivity of solution was investigated and explained. The SEPS was applied for the determination of the adsorption density of dicetyldimethyl-ammonium bromide onto quartz surface. (C) 1998 Elsevier Science S.A. All rights reserved.