Drugs coated-wire electrodes

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. 

Rote et al. (1993, 1994) used a carotid thrombosis model in dogs. A calibrated electromagnetic flow meter was placed on each common carotid artery proximal to both the point of insertion of an intravascular electrode and a mechanical constrictor. The external constrictor was adjusted with a screw until the pulsatile flow pattern decreased by 25 % without altering the mean blood flow. Electrolytic injury to the intimal surface was accomplished with the use of an intravascular electrode composed of a Teflon-insulated silver-coated copper wire connected to the positive pole of a 9-V nickel-cadmium battery in series with a 250000 ohm variable resistor. The cathode was connected to a subcutaneous site. Injury was initiated in the right carotid artery by application of a 150 xA continuous pulse anodal direct current to the intimal surface of the vessel for a maximum duration of 3 h or for 30 min beyond the time of complete vessel occlusion as determined by the blood flow recording. Upon completion of the study on the right carotid, the procedure for induction of vessel wall injury was repeated on the left carotid artery after administration of the test drug. 

An example of CWE with a coated silver wire can be a sensor of benzalko-nium chloride [47] containing in the polymer matrix benzalkonium-phosphomolyb-date (Bz-PM) as the active complex. Compared to a classic sensor, this electrode shows a wider range of linearity from 2.0 x 10 to 1.0 x 10" mol L with a Nernstian slope of 60 0.3 mV/decade and lower detection limit of 2.0 x 10" mol L. The electrode shows good selectivity toward inorganic and organic ions, sugars and some common drug excipients. It can be used for determination of benzalkonium chloride in pharmaceutical preparations in the form of eye, nose and ear drops. 

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