A voltammetric sensor for (-)-ephedrine has been prepared by a novel approach based
on immobilisation of an imprinted polymer for ephedrine (MIPE) in an electrosynthesised
polypyrrole (PPY) film. Composite films were grown potentiostatically at 1.0 V vs.
Pt (QRE) on a glassy carbon electrode using an unconventional "upside-down" (UD) geometry
for the three-electrode cell. As a consequence, a high MIP loading was obtained, as
revealed by SEM. The sensor response was evaluated, after overoxidation of PPY matrix,
by cyclic voltammetry after pre-concentration in a buffered solution of analyte in
0.5-3 mM concentration range. An ephedrine peak at approximately 0.9 V increasing
with concentration and saturating at high concentrations was evident. PPY-modified
electrode showed a response, which was distinctly lower than the MIP response for
the same concentration of the template. The effect of potential interferences including
compounds usually found in human fluids (ascorbic acid, uric acid, urea, glucose,
sorbitol, glycine, dopamine) was examined.