Frans_M_Everaerts_Isotachophoresis_378342.pdf

REFERENCES 81
Fig.4.17. Relationship between the measured step heights, as found in the linear trace of the
thermometric signal, and the calculated zone resistance for some anions in the operational system
at pH 7 (see Table 12.2), without corrections (left) and with corrections (right).
the mobility, have been neglected. Consequently, the resistances of the zones increase.
As these effects are stronger for divalent ionic species, two different curves can be
expected, as illustrated. The influence of the different temperatures on the pK values and
ionic mobilities and the influence of the activity coefficients do not differ very much
for mono- and divalent ionic species.
After corrections have been made for the effects of temperature, activity coefficients
and the Onsager relationship, only one curve is obtained for both mono- and divalent ionic
species (Figs.4.15b, 4.16b and 4.17b, in accordance with the theory. In all instances the
calculated pH values of the zones before and after applying the corrections do not differ
appreciably (not more than 0.01 pH unit for most ionic species). Therefore, no pH measure-
ments were used as a check on the theory. Reasonable values were obtained, however, by
Everaerts and Routs [ 111 .
REFERENCES
1 R. A. Alberty, J. Amer. Chem. Soc. 72, 2361, 1950.
2 J.L. Beckers, Thesis, University of Technology, Eindhoven, 1973.
3 J.L. Beckers and F.M. Everaerts, J. Chromatogr., 51 (1970) 339.
4 J.L. Beckers and F.M. Everaerts, J. Chromatog., 68 (1972) 207.
5 M. Bier, Electrophoresis, Vols. I and 11, Academic Press, New York, 1959 and 1967.
6 G. Brouwer and G.A. Postema, J. Electrochem. SOC., 117 (1970) 7 and 874.