Sulfate-selective electrode based on a bis-thiourea ionophore

Abstract

A new coated graphite sulfate-selective electrode based on the use of the anion receptor N-[4-[4-[(anilinocarbothioyl)amino]benzyl]phenyl]-N-phenylthiourea in poly(vinyl chloride) matrix is reported. Addition of cetyltrimethylammonium bromide and various plasticizers (2-nitrophenyl octyl ether, dibutyl phthalate, dioctyl phthalate, and chloronaphthalene) was found to substantially improve the performance of the sensor. The electrode showed a Nernstian response for SO 4 2− ions over a wide activity range (3.0 × 10−7–1.0 × 10−1 M) with a limit of detection of 1.9 × 10−7 M. The response time of the sensor was ~15 s, and the membrane could be used for more than 2 months without observing any deviation. The electrode revealed acceptable selectivity towards sulfate with respect to many common anions and also was used as an indicator electrode in potentiometric titration of sulfate and barium ions and in determination of sulfate in a pharmaceutical zinc sulfate capsule.