A new method for application of the water-soluble dye SPADNS in a carbon paste electrode for determination of trace amounts of copper.

2-(P-sulfophenylazo)-1,8-dihydroxy-3,6-naphthalene disulfate (SPADNS) was adsorbed on surfactant modified zeolite type A by electrostatic interaction in the aqueous phase. The dye was strongly retained and not easily leached from the surfactant-modified zeolite matrix. This compound was incorporated into a carbon paste electrode for anodic stripping voltammetric determination of trace amounts of copper. The calibration plot was linear over the copper concentration range 2.0-800 microg/L. The detection limit was found to be 0.4 microg/L Cu(II), and for 5 successive determinations of 50 and 150 microg/L Cu(II) the relative standard deviations were 1.6 and 1.2%, respectively. The modified electrode prepared in this study could be used for the determination of Cu(II) in water samples and human hair with good results.