Frans_M_Everaerts_Isotachophoresis_378342.pdf

296 SEPARATION OF ANIONIC SPECIES IN AQUEOUS SOLUTIONS
TABLE 12.1
OPERATIONAL SYSTEM AT pH 6 SUITABLE FOR ANIONIC SEPARATIONS
Solvent: H,O and D,O.
Electric current &A): Cu. 50-100.
Purification: Morpholinoethanesulphonic acid (MES) is recrystallized three times and the
crystals are washed with acetone.
Electrolyte
Leading Terminating
Anion cl- E.g., MES-
Concentration 0.01 N Cu. 0.01 N
Counter ion Histidine' Tris+
PH 6.02 Cu. 6
Additive 0.05% Polyvinyl None
alcohol (Mowiol)*
*For experiments with a thermometric detector, this additive is not necessary.
TABLE 12.2
OPERATIONAL SYSTEM AT pH 7 SUITABLE FOR ANIONIC SEPARATIONS
Solvent : H, 0.
Electric current hA): Cu. 50-100.
Purification: Morpholinoethanesulphonic acid (MES) is recrystallized three times and the
crystals are washed with acetone.
Electrolyte
Leading Terminating
Anion c1- E.g., MES-
Concentration 0.01 N Ca. 0.01 N
Counter ion Imidazole+ Tris'
PH 7.05 Ca. 6
Additive 0.05% Polyvinyl None
alcohol (Mowiol)*
*For experiments with a thermometric detector, this additive is not necessary.
12.1.2. Operational system imidazole/imidazole hydrochloride (pH 7)
In this operational system, the absolute mobility of the counter ion (imidazole) is
greater than in the operational system listed in Table 12.1 in which histidine is the counter
ion. This means that all zone resistances are lower and consequently all step heights are
smaller. The resolution will also be decreased by the more mobile counter ion. Thls was
found particularly in experiments with a conductivity detector.