Rapid Monitoring of Copper Over a Wide Concentration range by High-Sensitive Potentiometric Membrane Electrode Based on 1-cyano-1-piperidino-2(N- piperidino methyl)-cyclo hexane

Abstract

n this paper, 1-cyano-1-piperidino-2(N- piperidino meth-yl)-cyclohexane was synthesized. The lowest-energy conformer of this molecule (Ligand) with axial and equatorial forms of cyanide toward cyclohexane and local minima corresponding to their complexes with various ions were obtained using Monte Carlo procedure by Molecular Mechanics with MMFF94 method. The calculated results of the Gibbs free energy of the reaction using density functional theory (DFT) show that the thermodynamic reactivity of complexation of copper ion with studied ligand is the best. Finally, a selective and sensitive copper-ion selective liquid membrane electrode for potentiometric monitoring of ultra-trace amounts of Cu2+ was prepared by using 1-cyano-1-piperid-ino-2(N- piperidino methyl)-cyclohexane as an excellent ionophore. This electrode exhibits a Nernstian response for Cu2+ ions over a con-centration range (1.5 × 10-2 to 1.0 × 10-8 mol L-1) with a slope of 28.4±0.4 mV per decade. The limit of detection of the sensor is 6.3 × 10-9 mol L-1. The sensor has a relatively fast response time (<10 s) and a useful working pH range of 5.0–8.5. Interference of some cations was also evaluated. The practical utility of the Cu2+ ion sensor has been demonstrated by using it as an indicator electrode in potentiomet-ric titration of Cu2+ with EDTA and for direct determination of Cu2+ in well water samples.