Miss/Mrs Singh,

There is not ''free ion'' in solution. Thus, by means of potentiometric titration there is unable to determine ''free ion'' in solution. There is determined only the corresponding auqtic complex species or other species, depending on the pH of the solution.

If your study aims at determining quantitatively ''isolated'' ion of a metal, then there is needed a mass spectrometric based quantification. However, it should be based on our innovative stochastic dynamic theory and own-authored (mine and to my co-author's one according the published authorship detail) model equations, which provide exact or absolute analytical quantitative information.

Only by means of our theory currently, there is able to account precisely, selectively, sensitively and accurately for the mass spectrometric 'intensity' values of the isotopes of the metal ions; and for the experimental isotope ratio(s.)

Please, consider the content of our works [1,2]. Work [1] details on MS characteristics of isolated Ag-ions within the framework of our innovative theory, while work [2] details on its application to quantify directly analytes in solution. It is tested, so far, at concentration levels of analytes at pg.(mL)-1 and ng.(L)-1. The coefficients of linear correlations between our formulas and the experiment are /r/ = 0.99997 - 1.

[1] Journal of Molecular Liquids, 292 (2019) 111307

Stochastic dynamic electrospray ionization mass spectrometric diffusion parameters and 3D structural determination of complexes of AgI–ion – Experimental and theoretical treatment

Bojidarka Ivanova, Michael Spiteller

[2] Steroids, 164 (2020) 108750

Stochastic dynamic mass spectrometric quantification of steroids in mixture — Part II

Bojidarka Ivanova, Michael Spiteller