Abstract
A bridge modified 4-tert-butylthiacalix[4]arene (
I) has been employed as electroactive material in the preparation of cobalt selective sensor. Polyvinyl chloride (PVC)-based membranes of (
I) using sodium tetraphenylborate (NaTPB) as anion discriminator and bis(2-ethylhexyl) sebacate (DOS), chloronaphthalene (CN), tri-
n-butylphosphate (TBP),
o-nitrophenyl octyl ether (NPOE), tris(2-ethylhexyl)phosphate (TEHP) as plasticizers were prepared and investigated as cobalt selective sensors. A number of membranes of different compositions were prepared and investigated. The best performance was observed with the membrane having composition of 2:66:1.5:127 (mg)
=
I:NaTPB:PVC:NPOE. The potential response of this membrane is linear to Co
2+ ions in the concentration range 5.3
×
10
−6 to 1.0
×
10
−1
M with near-Nernstian slope of 30.0
mV/decade of activity and a detection limit of ∼0.3
ppm. This membrane also showed lowest response time of 10
s and works satisfactorily in partially non-aqueous medium. The selectivity studies of this sensor, evaluated with fixed interference method and matched potential method, show that the sensor under consideration possesses excellent selectivity for Co
2+ over a large number of mono-, bi- and trivalent cations such as Na
+, K
+, Ag
+, Ca
2+, Mg
2+, Cu
2+, Hg
2+, Pb
2+, Li
+, Ba
2+, Zn
2+, Sr
2+, Cr
3+, Ni
2+, etc. The sensor could be used as an indicator electrode in the quantification of Co
2+ by potentiometric titration against EDTA as well as in determination of cobalt content in wastewater and beer samples.