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-mercaptoben zothiazole (MBTH), and hexathiacyclooctadecane (HT18C6) carriers, in plasti cized poly(vinyl chloride) (PVC) matrix, are described. The influences of m embrane 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), an d 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 with out 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.