a b s t r a c t A polymeric membrane-based ion-selective electrode (ISE) for the determination of l-ascorbic acid (l-AA) was developed. The sensor was fabricated by modifying glassy carbon electrodes with molecularly imprinted polypyrrole (PPy) synthesized by electropolymerization of the monomer in the presence of ascorbate. A comparison between the non-imprinted modified electrode (PPy-NIP) and the molecularly imprinted polymer (PPy-MIP) is reported. The molecularly imprinted polymer improves the perfor-mances of the sensor, especially if the PPy film has been submitted to an oxidation treatment. The PPy-MIPox electrode shows near-Nernstian response (approx. −57 mV/decade) to the ascorbate over the concentration range between 5 × 10 −6 M and 2 × 10 −3 M and it can be used for more than 3 weeks without any considerable change in the measured response. The potentiometric sensor has been suc-cessfully applied to the determination of ascorbate in food and pharmaceutical samples (recoveries of about 100%).