Cationic surfactant ion-selective PVC membrane electrode containing macrocyclic diimine crown ether

DP- ion-selective PVC membrane electrode based on 2,3,11,12-dibenzo-5,9-dia za-4,9(10)-cis-diimino-1, 13-dioxacyclopentadecane as a novel macrocyclic d iimine crown ether is proposed. o-Nitrophenyl octyl ether as plasticizer an d potassium tetrakis(4-chlorophenyl)borate as lipophilic salt were used. Th e electrode exhibits a Nernstian response for 1.0 x 10(-2)-1.0 x 10(-6) mol l(-1) DPCl with a slope of 58 mVdecade(-1). The detection limit is 2.5 x 1 0(-7) mol l(-1). The electrode response was stable over a wide pH range (3- 11). The lifetime of the electrode was about 2 months. The electrode shows a high selectivity towards inorganic cations. Among the organic cations tes ted, only hexadecyltrimethylammonium ion interferes. The electrode was suit able for determining the critical micelle concentration and as an end-point detector in the potentiometric titration of the cationic surfactants.