Study on the mechanism of potential response of a ketamine-sensitive membrane electrode

The response mechanism of a simple device for the rapid detection of ketamine with 'in the field' capabilities is investigated. The mechanism is a membranous ketamine ionic selective electrode (ISE) with partly carboxylated PVC as matrix and ortho-nitrophenyloctyl ether (o-NPOE) as plasticizer. The experimental results reveal that the inclusion of the plasticizer in the membrane significantly increased the response. A mechanism is proposed where the infiltration of a target species into the membrane is capable of producing a superior response. This response process is non-selective for species with similar molecular structure and size. This new research addresses some omissions and misapprehension in the literature where the mechanism was reported as an ion-exchange-induced response. In this research the ion-exchange-induced response was measurable after the elimination of the infiltration-induced response extending to lower concentration ranges and thus providing the potential for better sensitivity and selectivity.