Low Cost Electrochemical Sensors for Silver, Chloride, Bromide and Iodide Ions

Abstract

Low cost all solid state pressed pellet Ag⁺, halides and sulphide sensitive electrodes based on silver sulphide were fabricated. The electrodes have been tested and results compare favorably with commercial electrodes. Pure Ag₂S electrode with internal silver metal contact was found to follow Nernstian equation from 1 x 10^-1 to 1 x 10^-5 M of silver ion with slope equal to 59.8 mV per decade change in concentration of Ag⁺ - ion. Electrodes fabricated from equimolar mixture of Ag₂S and Ag - halide was found to be sensitive to the respective halide and silver ions. Iodide ion selective electrode prepared from a equimolar mixture of Ag₂S and AgI was found to be selective to iodide ion with negligible interference from bromide and chloride ions. The potentiometric selectivity coefficient K^pot _I,Br, K^pot _I,Cl were found to be 1.77x10^-2 and 7.94x10^-3 respectively. All these electrodes were found to be selective to Ag⁺ ion with negligible interference with K^pot _{Ag, Hg} equal to 1 x 10^-5 Hg⁺⁺ ion with selectivity coefficient.

Keywords: Ion selective electrodes; Potentiometric selectivity coefficient; Silver sulphide.  

DOI: 10.3126/sw.v6i6.2631

Scientific World, Vol. 6, No. 6, July 2008 33-36