Contact hybrid potentiometric method for on-site and in situ estimation of the antioxidant activity of fruits and vegetables

A new version of the hybrid potentiometric method (HPM) for evaluating the antioxidant activity (AOA) of fruits and vegetables, which we called contact (CHPM), is proposed. A screen-printed electrode pair coated by a membrane impregnated with a mediator serves as a sensor system. The potential shift, which is observed when the sensor system is exposed to the sample slice is used as a source of information. CHPM provides reproducible and correct results: relative standard deviation does not exceed 8.4% and recovery of model antioxidant at close to 100%. The AOA values of fruits and vegetables found by CHPM are in the range of 1-21 mu mol-eq/g. Correlation between the AOA of slices and suspensions is found. The proposed CHPM can be used in on-site and in situ formats.