In the present research, a microneedle Cu (II) selective electrode based on conducting polypyrrole (PPy) doped with 8-hydroxyquinoline-5-sulfonic acid (8-HQS) is introduced. 8-HQS which has been incorporated into the polypyrrole backbone during electropolymerization acts as an active ionophore for Cu (II) ion recognition. Several relevant factors affecting the sensor performance have been investigated and optimized. The proposed electrode showed a linear response over the concentration range of 1.0 × 10−5 to 1.0 × 10−1 M with a sub-Nernstian slope of 22 ± 1 mV per decade change in Cu (II) concentration. The response time of the electrode was less than 10 s and the proposed electrode revealed good selectivity for Cu (II) over a wide variety of other ions and could be used in the pH range of 4.0–7.0. The electrode was successfully employed as an indicator electrode in potentiometric titration of Cu (II) ion with EDTA and also for direct determination of copper in spiked tap water and fruit juice samples. The proposed electrode presents special features such as simplicity of operation, capability of miniaturization of steel substrate, low cost, simple fabrication and suitability to be used as Cu (II) disposable electrode and for mass production.

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