Ion-selective polymeric-membrane electrodes with immobilised ion-exchange sites. Part II. Selectivity of and application studies on a calcium electrode

Abstract

A further study is reported of a calcium ion-selective electrode where the sensor is a dialkylphosphate group which is covalently bound to poly (styreneb-butadiene). Selectivity in the order Ca2+ > Ba2+ > Sr2+ > Mg2+ > M+ was found. Interference was encountered from transition metal cations but no irreversible poisoning was observed. The response to surfactants was found to be less than that exhibited by established electrodes. The performance of the covalently bound sensor electrode for the monitoring of coking-plant effluent has been compared with other analytical techniques. This electrode appears to offer advantages of robustness, reliability and improved lifetime over a commercial liquid membrane electrode and a PVC membrane electrode for this application.

Selectivity of membrane electrodes based on derivatives of dibenzyltin dichloride

“…Both of these methods are based on the extended Nernst equation (19), which is an empirical relationship that works well in modeling the nonspecific response of a membrane electrode when the ions under investigation have the same charge. This equation is not well suited, however, when ions of different charge are involved (6,(20)(21)(22)(23)(24). Coefficients are either deceptively large or small depending on whether the ion of higher charge is considered as the primary or interfering species.…”

Carrier-Based Ion-Selective Electrodes and Bulk Optodes. 1. General Characteristics

“…For miniaturized electrodes, covalent attachment of all membrane components including the ionophore is advisable. Both charged 282 and uncharged 175,176,283 ionophores have been covalently bonded to the polymer matrix, seemingly without any significant loss of electrode performance. The use of templates during polymer preparation was proposed as an alternative way of preparing selective electrodes.…”

Carrier-Based Ion-Selective Electrodes and Bulk Optodes. 2. Ionophores for Potentiometric and Optical Sensors

“…by the same authors log (FIM): Mg 2+ , −1.6; Cu 2+ , +1.0; Zn 2+ , −1.4; PVC, calcium didecyl phosphate, DOPP, DOP, nitrobenzene), is an interesting exception but loss of the membrane component nitrobenzene must be expected. Several attempts to covalently attach the ionophore to the matrix were made but were reported to fail to give the expected improvement in the electrode lifetime or to result in only a reduced selectivity. − …”