A potentiometric detector was developed for CE and
applied to the determination of aliphatic carboxylic acids
(up to C10). The electrodes used were of the “coated
wire”
type. Insulated Cu wires (from 100 to 250 μm
diameter),
with only the tip of the wire exposed, were directly
coated
with “liquid membrane” phases. A quaternary ammonium salt and a lipophilic macrocyclic pentaamine were
used as carrier molecules. The electrodes were positioned at the end of the capillary (“wall-jet” type of
construction). The best compromise between separation
and detection characteristics was obtained with a HEPES
buffer system. Detection limits of 100 fmol were
obtained
(injection by electromigration). Calibration curves
were
linear in the range of 0−25 pmol injected. The
behavior
of the detection system is discussed theoretically.
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