Abstract
The potentiometric response characteristics of mercury ion-selective membrane electrodes based on 2-amino-6-purinethiol (I(1)) and 5-amino-1, 3, 4-thiadiazole-2-thiol (I(2)) were described. Ion selectivities were tested for various plasticizers, which were used as solvent mediators to incorporate the ionophores into the membrane. Effects of experimental parameters such as membrane composition, nature and amount of plasticizers and additives, pH and concentration of internal solution on the potential response of Hg(2+) electrodes were investigated. The best performance was obtained with the electrode having a membrane composition (w/w) of (I(1)) (3.17%): PVC (31.7%): DOP (dioctylpthalate) (63.4%): NaTPB (sodium tetraphenylborate) (1.58%). The proposed electrode reveals a Nernstian response over Hg(2+) ion in the concentration range of 7.0 x 10(-8)-1.0 x 10(-1) M with limit of detection 4.4 x 10(-8) M. The electrode shows good discrimination toward Hg(2+) ion with respect to most common cations. It shows a short response time (10s) for whole concentration range and can be used for 2 months without any considerable divergence in potentials. For evaluation of the analytical applicability, the electrode was used in the determination of Hg(2+) ion in different environmental and biological samples. The practical utility of the membrane electrode has also been observed in the presence of surfactants.