Determination of copper (II) in solution using a twinned piezoelectric quartz crystal coated with chitosan

Abstract

A twinned piezoelectric quartz crystal (PQC) was constructed with two of one electrode-separated PQCs, one of which oscillates separately. One of them was coated with a functional polymer film which could adsorb an analyte and the other with a polymer film having the same frequency behavior against the liquid properties, except for the adsorption of an analyte. Thus, the different frequency behaviors between the one electrode-separated PQCs result mainly from the adsorption of the analyte. On the other hand, the frequency behavior caused by the chitosan coating could be controlled with a coating of cellulose acetate on the other PQC. By controlling the experimental conditions, the twinned PQC selectively adsorbed copper (II), and the frequency change was proportional to the concentration. The adsorption of copper (II) onto chitosan, however, increased with the frequency. It was supposed that the adsorbed water on the chitosan with the hydrogen bond was removed by complexing with cupper (II), and then the frequency was increased because of decreasing mass on the chitosan.