Mercury selective membrane electrodes using 2-mercaptobenzimidazole, 2-mercaptobenzothiazole, and hexathiacyclooctadecane carriers

The construction, performance, and applications of coated-wire mercury(II)-selective electrodes based on 2-mercaptobenzimidazole (MBIM), 2-mercaptobenzothiazole (MBTH), and hexathiacyclooctadecane (HT18C6) carriers, in plasticized poly(vinyl chloride) (PVC) matrix, are described. The influences of membrane composition and pH on the potentiometric response of the electrodes were investigated. The electrodes exhibit near-Nernstian responses for Hg2+ ion over a wide concentration range (4 to 5 decades of concentration), and a detection limit of about 6 x 10(-7) M (for the electrode based on MBTH). The response time of the electrodes is between 20 and 100 s, depending on the concentration of mercury, and they can be used for about 2 months without any considerable divergence in potential. The proposed sensors revealed good selectivity for Hg2+ in the presence of several metal ions. The best selectivity was observed for the electrode based on MBTH carrier. They were used as indicator electrodes in the potentiometric titration of Hg2+ with EDTA and for the determination of mercury in waste water samples. (C) 2000 Elsevier Science B.V. All rights reserved.