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

The sensitivity of a capacitive penicillin sensor based on a pH-sensitive electrolyte–insulator–semiconductor (EIS) sensor with respect to four different kinds of penicillin is investigated. A total of 10 μl of a solution containing penicillin G, ampicillin, amoxicillin or cloxacillin, respectively, 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 possible pH interference, all measurements are performed with a penicillin sensor as well as with a pH sensor. The resulting calibration curves show no sensitivity for cloxacillin and nearly equal sensitivities for the other three kinds of penicillin. Lower detection limits of about 0.05 μg are obtained for penicillin G, ampicillin and amoxicillin.