A Simple and Selective Flow-Injection Potentiometric Method for Determination of Iodide Based on a Coated Glassy Carbon Electrode Sensor

• Published in: International journal of electrochemical science Vol. 2; no. 10; pp. 778 - 787
• Main Authors: Beheshti, Saeed S., Amini, Mohammad K.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.10.2007; Elsevier
• Subjects: Bis(4-chlorothiophenolato)mercury (II); Flow-injection analysis; Iodide; Membrane electrode; Potentiometry; Iodide; Membrane electrode; Bis(4-chlorothiophenolato)mercury (II); Potentiometry; Flow-injection analysis
• ISSN: 1452-3981; 1452-3981
• DOI: 10.1016/S1452-3981(23)17111-2

A flow-injection (FI) method is reported for the determination of iodide based on potentiometric detection, using a membrane electrode containing bis (4-chlorothiophenolato)mercury (II) [Hg(CTP)2] as the active component. The response of the system was evaluated with regard to the parameters of the membrane electrode and the FI system. The calibration curve for iodide at the optimized conditions including 0.01 M sodium sulfate (pH 6.0) carrier solution with a flow rate of 1 mL min-1 and an injection volume of 100 mL was linear over the range 1.0×10-6-7.6×10-2 M with a Nernstian slope of - 59.4 mV per decade of iodide activity. The influence of several common inorganic and organic anions on the response of the FI system was investigated and selectivity coefficients were evaluated. The sensor shows high selectivity towards iodide, which can be related to the selective interaction of iodide as a soft anion with mercury atom in Hg (CTP)2 as a soft metal center. This is certified by the very low tendency of the sensor towards chloride, bromide, and the highly lipophilic anions such as perchlorate, salicylate, nitrate, nitrite, and thiocyanate. The system exhibited a fast response time of less than 5 s (in the batch mode), a detection limit of 5.0×10-7 M and a relative standard deviation of 0.6% at 0.1 mM iodide. The sampling frequency was between 40-120 h-1 depending on the concentration of iodide in the measuring solution. The proposed system was applied to the determination of iodide in a pharmaceutical preparation and the results were compared with a standard potentiometric method based on silver indicator electrode.