Cross-sensitivity of a capacitive penicillin sensor combined with a diffusion barrier

The sensitivity of a capacitive penicillin sensor based on a pH-sensitive e lectrolyte-insulator-semiconductor (EIS) sensor with respect to four differ ent kinds of penicillin is investigated. A total of 10 mu l of a solution c ontaining penicillin G, ampicillin, amoxicillin or cloxacillin, respectivel y, are dried on a plastic disc as a diffusion barrier which is then brought in contact with the sensor. In order to correct the sensor signals for a p ossible pH interference, all measurements are performed with a penicillin s ensor as well as with a pH sensor. The resulting calibration curves show no sensitivity for cloxacillin and nearly equal sensitivities for the other t hree kinds of penicillin. Lower detection limits of about 0.05 mu g are obt ained for penicillin G, ampicillin and amoxicillin. (C) 2000 Elsevier Scien ce S.A. All rights reserved.