Synthetic zeolite modified electrode as a sensor for determination of trace amount of copper

2-(p-sulfohenylazo)-1, 8-dihydroxy-3, 6-naphthaleindisulfate (SPADNS) was adsorbed on modified LTA zeolite by electrostatic interaction in aqueous phase. The dye is strongly retained and not easily leached from the modified zeolite matrix. The solid was characterized by XRD prior to using it for the electrode preparation. This compound was incorporated into a carbon paste electrode for cyclic and differential pulse voltammetric measurements. SPADNS immobilized on the support had not electrochemical response in the potential region between (-1-0.5V). The electrode made with this material was used for the determination of trace amount of copper. The anodic peak current observed in differential pulse voltammetry was linearly dependent on the copper concentration. At a fixed potential under static conditions, the calibration plot was linear over the copper concentration range 3 ppb to 0.8 ppm. The detection limit of the method is 1.3 ppb, low enough for trace copper determination in various real samples.