Solvent mediator studies on barium ion-selective electrodes based on a sensor of the tetraphenylborate salt of the barium complex of a nonylphenoxypoly-(ethyleneoxy)ethanol

Abstract

The barium ion-selective electrode sensor based on the neutral carrier complex of a nonylphenoxypoly(ethyleneoxy)ethanol containing 12 ethylene oxide units and 2 mol of tetraphenylborate ion per mole of Ba²⁺(12 EOU. Ba.2TPB) requires a more viscous solvent mediator than 4-nitroethylbenzene for long-life poly(vinyl chloride)(PVC) matrix-membrane barium ion-selective electrodes. Both 2-nitrophenyl octyl ether and di-2-nitrophenyl ether used in conjunction with the sensor in a PVC matrix membrane give functional barium ion-selective electrodes, but those with di-2-nitrophenyl ether mediator are far superior with lifetimes of about 30 d. Barium ion-selective electrodes with the sensor and mediator in liquid membranes can be made for a wide range of nitro-aromatic solvent mediators.

Barium ion-selective electrodes made from discs taken from a master membrane containing 0.40 g of a saturated solution of Antarox CO-880. Ba.-2TPB in di-2-nitrophenyl ether can be used as indicator electrodes for the potentiometric titration of SO₄^2– with Ba²⁺. A role for a potentiometric titration finish in the determination of sulphur in organic compounds by the oxygen-flask method is recommended.