Home Made Ion-selective Electrodes for Education

All solid-state ion-selective electrodes (ISEs) based on silver sulphide pressed pellets were fabricated. The electrode was found to be sensitive and selective to Ag+ and S(-)ions, and followed the Nernstian behavior in the concentration of 1 x 10(-1) to 1 x 10(-5)M with slope of 31.5 mV and 57.5 mV per decade change in S(-)and Ag+ ion concentrations, respectively. The electrode was used to determine the solubility products of Ag2CrO4, AgBrO3, and AgSO4 and the amount Of H2S in the cigarette smoke. The average amount Of H2S per stick of a cigarette was found in the range of 0.0332 to 0.0766 mg. The iodide, bromide, and chloride selective electrodes were also fabricated by incorporating appropriate amount of AgI, AgBr, and AgCl in silver sulphide. The potentiometric selectivity coefficients of the iodide for bromide (K-I-Br-(pot) and chloride ions (K-I-Cl-(pot) were found to be 1 x 10(-2) and 5 x 10(-3), respectively. The LaF3 single crystal electrode was used to determine the fluoride ion in fluorinated toothpaste and tea samples. The sensitivity and reliability of these home made ISEs were comparable to the commercial electrodes. Therefore, we believe that the thus prepared electrodes will play a pivoted role in teaching of analysis with ion-selective electrode.