Frans_M_Everaerts_Isotachophoresis_378342.pdf

SEPARATION USING A THERMOCOUPLE AS DETECTOR 289
Fig.ll.3. Simultaneous separation of some cations in the system WKAC. Abbreviations as in Fig.11.1.
9
-
f
i,
Fig.ll.4. Isotachopherogram of the separation of some cations in the system WKAC, using a thermo-
metric detector. 1 = Kt; 2 = Ba”; 3 = Ca? 4 = Na’; 5 = Ni”; 6 = Cd2+; 7 = Pb2+; 8 = (C,H,), W;
9 = Trist. T = Increasing temperature; t = time.
11.1.4. The system WKCAC
The leading electrolyte is potassium hydroxide in water, adjusted to pH 6.37 by
adding cacodylic acid Tris’ is used as the terminating ion. This higher pH was chosen so
as to investigate the effect of increased pH.
In the system WKCAC, all ions have lower effective mobilities owing to the higher pH
(some cationic species have pK values between 5 and 7) and to complex formation. The
effective mobilities of N3+, Cr3+ and Fe3+ are too low. Imidazole shows a typical shift in
step height. It has a pK value of 6.95 and at higher pH its effective mobility will decrease.