Frans_M_Everaerts_Isotachophoresis_378342.pdf

SEPARATION USING CONDUCTIVITY AND UV DETECTORS 303
Fig.12.4. Isotachopherograms of the separation of the oxidation products of acetylsalicylic acid in
two different operational systems. (a), Reaction mixture before oxidation, analysis carried out in
the operational system at pH 6 (Table 12.1); (b), reaction mixture after oxidation, analysis carried
out in the operational system at pH 6 (Table 12.1); (c), reaction mixture after oxidation, analysis
carried out in the operational system at pH 3.2 (Table 12.6). The current was stabilized at 80 PA.
1' = Chloride; 2' = acetate; 3' = salicylate and phosphate; 4' = acetylsalicylate; 5' = MES; 1 = chloride;
2 = phosphate; 3 = salicylate; 4 = acetylsalicylate; 5 = acetate; 6 = propionate. A = increasing UV
absorption; R = increasing resistance; t = time.
with a smaller effective mobility than that of the leading ion, in this particular
instance the chloride ion. The reproducibility of these analyses, performed with a
sample tap, proved to be better than 2%. Nevertheless, a more mobile ion than chloride
was sought. The literature indicates that the Fe(CN6)& ion is a fast moving ion at infinite
dilution and is much faster than the chloride ion. For this reason, three operational
systems we re prepared :
i
for Fig.12.7a: 0.01 N Fe(CN6)4- with 0.02 N histidine;
for Fig.12.7b: 0.005 N Fe(CN6)" with 0.01 N histidine;
for Fig.12.7~: 0.001 N Fe(CNJ4- with 0.002 N histidine.
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