Frans_M_Everaerts_Isotachophoresis_378342.pdf

REFERENCES 113
Example I. As example C shows, pronounced differences in effective mobilities can be
expected if instead of water methanol is used as solvent. Example G shows some differences
in effective mobilities, due to the change in pH. The differences in the effective
mobilities, as found in the various systems, always must be interpreted carefully. The
influence of the counter ion, the solvent and the pH always results in changes in the
effective mobilities of the various ionic species considered. Therefore another example of
these various effects can be given.
Fig.5.12 shows clearly the influence of the various systems on the effective mobilities
(step heights) of the cations. The systems WHCl, WAC, MHCl and MKAc are listed in
Tables 11.1, 11.3, 16.4 and 16.5, respectively.
The behaviour of the cations K, Na and Li is similar, while highly charged cations such
as Ce, Al and Pb show shifts due to effects of pH and complex formation. A large shift is
shown for the tetraethylammonium ion in the aqueous and methanolic systems due to the
effect of solvation and change of dielectric constant of the solvent.
Much more information about this subject can be found in the literature considering
“structure breaking” and “structure making” properties of ionic species.
Moreover, in methanolic systems the influence of a change in pH on the divalent
cations is remarkable.
REFERENCES
1 J. Deman, Anal. Chem, 43 (1970) 321.
2 R.P. Bell, Acids and Bases, Methuen, London, 2nd ed., 1969.
3 G. Schwarzenbach, Helv. Chim Acta, 13 (1930) 870.
4 J. Dingemans, Electrochemie, Waltman, Delft, 5th ed., 1964.
5 R.G. Bates, Electrometric pH Determinations, Wiley, New York, 1964.
6 C.L. de Ligny, P.F.M. Luykx, M. Rehbach and A.A. Wieneke, Rec. Trav. Chim. Pays-Bas, 79
(1960) 699.
7 C.L. de Ligny, P.F.M. Luykx, M. Rehbach and A.A. Wieneke, Rec. Trav. Chim Pays-Bas, 79
(1960) 713.
8 R.M. Fuoss,J. Amer. Chem. SOC., 79 (1957) 3301.
9 R.M. Fuoss and L. Onsager, J. Phys. Chem., 61 (1957) 668.
10 W.J. Gelsema, Thesis, University of Utrecht, Utrecht, 1964.
11 C.L. de Ligny, Thesis, University of Utrecht, Utrecht, 1959.
12 C.L. de Ligny and M. Rehbach, Rec. Trav. Chim Pays-Bas, I9 (1960) 727.
13 J. Kucharsk; and L. Safarik, nitrations in Non-Aqueous Solutions, Elsevier, Amsterdam, 1965.
14 D.B. Rorabacher, W.J. MacKellar, F.R. Shu and M. Bonavita, Anal. Chem. 43 (1971) 561.