Copper-sensitive membrane electrode

The 14-membered macrocyclic phosphine 77 and corresponding sulfide 78 were prepared by the macrocyclization under high dilution conditions and further oxidation with sulfur (Scheme 12.29). Both ligands were used as ionophores in an all-solid state poly(vinylchloride) matrix membrane electrode. The sulfide 78 based electrode exhibited a Nemstian response towards copper (II) ions with a cationic slope of 30.7 mV/pCu and a detection limit of 5.97 x 10 M. The potential response remains almost unchanged over the pH range 3.9-6.4 at least 7 months. Sensors based on the macrocycles 77 and 78 demonstrate the copper (11) ion sensitivity over other metal ions [83]. 

A.K. Jain, R.P. Singh, and C. Bala, Solid membranes of copper hexacyanoferrate(III) as thallium(I)-sensitive electrode. Anal. Lett. 15, 1557-1563 (1982). 

Satake et al. reported the use of a coated wire electrode sensitive to procaine and other local anesthetic cations, and their application to potentiometric determination [73]. Electrodes were constructed from a copper wire (0.8 mm diameter), coated with a PVC membrane comprising a mixture of the drug-tetraphenylborate ion-pair, dioctyl phthalate, polyvinyl chloride, and tetrahydrofuran. Potential measurement was made with respect to a Ag-AgCl reference electrode. The electrodes showed linear responses with a Nemstian slope for procaine over the concentration range investigated. The method was used for analyses of the drug in pharmaceutical preparations. 

In independent studies, fullerene has been widely used as an electron mediator in electrodes, since the incorporation of significantly reduces the electrical resistance of the coating membrane. By way of example, an iodide-sensitive sensor was reported (Wang et al. 1996) in which the bilayer lipid membrane supported on a copper wire—which acted as a modified electrode—also contained fullerene. The resulting electrode was further used in a three-electrode system for the determination of iodide in solution, obtaining a detection limit of 10 nM. 

Based on the coated silver and copper wire design, an electrode for determination of quininium cation was developed [48], The ion-sensitive compounds dissolved in the polymer membrane were reineckate (Rn ), phosphotungstate (PT ) and phosphomolybdate (PM ) ions. The electrodes were tested in terms of deviation, life span, pH effect and the effect of the interfering ions. The electrodes were used in practice for determination of an active ingredient in pharmaceutical preparations. Studies show that the Ag-coated electrode with phosphotungstate as the anti-ion shows different properties in terms of precision of determination and the preferences of the silver electrode as the internal reference. 

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