An Improved Standard Addition Method with an Ion-Selective Electrode

Abstract

An improved standard addition method in which neither electrode potential nor response slope of an ion-selective electrode is required for linear plots is proposed.
A sample solution, of volume V, is titrated with a solution con taining a known amount (cs)of the same ion to be determined and subsequently with a diluent at a constant ionic strength. If the volumes which correspond to the identical electrode potential on the titration curves are. read off and denoted by vs and v respectively, the concentration, cx, of the analyte is determined from a slope of a linear plot of y vs. x:
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where x=vvs, y=vs(V-I-v), p is a constant.
Concentrations of fluoride solutio ns ranging from 10-2 to 10-5mo1dm-3 were determined with an error of less than O.3% and a coefficient of variation of less than 0.4%.