Iodide Selective Electrodes Based on Bis(2-mercaptobenzothiazolato) Mercury(II) and Bis(4-chlorothiophenolato) Mercury(II) Carriers

Mohammad Amini,Mohammad Habibi,Ali Rafi,Mehrorang Ghaedi,Morteza Zohory

doi:10.3390/s31100509

Abstract

New iodide-selective electrodes based on bis(2-mercaptobenzothiazolato) mercury(II) [Hg(MBT)2] and bis(4-chlorothiophenolato) mercury(II) [Hg(CTP)2] carriers are described. The electrodes were prepared by incorporating the ionophores into plasticized PVC membranes, which were directly coated on the surface of graphite disk electrodes. The electrodes displayed high selectivity for iodide with respect to a number of inorganic and organic anions. The influence of the membrane composition and pH, and the effect of lipophilic cationic and anionic additives on the response properties of the electrodes were investigated. The electrodes exhibited near-Nernstian slopes of -57.6 ± 0.8 and -58.4 ± 1.4 mV/decade of iodide concentration over the range 1 × 10-6 – 1 × 10-1 M, with detection limits of ~4 × 10-7 and 6 × 10-7 M for the electrodes based on [Hg(MBT)2] and [Hg(CTP)2], respectively. They have relatively fast response times (≤ 10 s), satisfactory reproducibility, and life times of at least two months. The potentiometric responses of the electrodes are independent of pH of the test solution over the range 3.5 – 11.5.

Highlights

Due to the importance of iodine as an essential micronutrient and its key role in many biological activities such as brain function, cell growth, neurological activities and thyroid function [1], numerous analytical methods have been reported for its determination at low concentration levels
These include gas chromatography with mass spectrometry detection [2]; ion chromatography with spectrophotometry [3] or mass spectrometry [4] detection; inductively coupled plasma atomic emission mass spectrometry [5]; neutron activation analysis [6]; chemiluminescence [7]; polarography [8]; cathodic [9] and anodic stripping voltammetry [10,11]; flow injection methods based on amperometry [1], spectrophotometry [12] or catalytic [13] detection; and potentiometry based on ionselective electrodes (ISEs)
One of the most important figures of merit for an ISE is its selectivity towards a specific analyte, which is generally limited by the interaction of the ionophore within the membrane with other ions

Summary

Introduction

Due to the importance of iodine as an essential micronutrient and its key role in many biological activities such as brain function, cell growth, neurological activities and thyroid function [1], numerous analytical methods have been reported for its determination at low concentration levels These include gas chromatography with mass spectrometry detection [2]; ion chromatography with spectrophotometry [3] or mass spectrometry [4] detection; inductively coupled plasma atomic emission mass spectrometry [5]; neutron activation analysis [6]; chemiluminescence [7]; polarography [8]; cathodic [9] and anodic stripping voltammetry [10,11]; flow injection methods based on amperometry [1], spectrophotometry [12] or catalytic [13] detection; and potentiometry based on ionselective electrodes (ISEs). It has been shown that the anion selectivity of the membrane electrodes that are based on metal complexes is influenced by both the structure of the ligands and the properties of the metal ions [14,15]

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