A Potentiometric Sensor Based on a Molecularly Imprinted Polymer Modified with Multi-Walled Carbon Nanotubes for the Selective Determination of Thiabendazole Residues in Fruit Peels

Thiabendazole (TBZ) is a widely used post-harvest fungicide for fruit protection. Therefore, a new potentiometric sensor for TBZ determination based on a molecularly imprinted polymer (MIP) modified with multi-walled carbon nanotubes (MWCNTs) was developed. Different plasticizers, amounts of sensor material, and MWCNTs were tested during sensor optimization. The best sensor response was obtained for the membrane containing dibutyl phthalate (DBP) as a plasticizer, 3 wt% sensor material, and 2 wt% MWCNTs. The selected sensor showed a slope of 59.7 mV/decade of activity, a limit of detection (LOD) of 3.2·10−7 M, and a wide measuring range (6.2·10−7–1.0·10−3 M). The response time was 4 s, with a stable signal and a potential drift of 0.72 mV/h. The sensor was applied for TBZ determination in standard solutions and prepared fruit-peel extracts (orange, banana, and lemon).