Preliminary Study on Electrosynthesis of a Co-Porphyrin Based Molecularly Imprinted Polymer for the Selective Detection of the Herbicide 2,4-Dichlorophenoxy Carboxylic Acid

This work represents the first attempt to the electrosynthesis of a molecularly imprinted polymer (MIP) employing a Co-porphyrin as monomer (Co(III)tetrakis o-aminophenyl porphyrin (CoTAPP)). UV-Vis spectroscopic studies were conducted to investigate interactions of the porphyrin with two toxic organohalides (4-(2,4-dichlorophenoxy) butyric acid (2,4-DB) and 2-(2,4-dichlorophenoxy) propionic acid (2,4-DP)). Binding constants of the complexes between CoTAPP and each organohalide was evaluated by Scatchard plots. Collected data evidenced a more significant interaction with 2,4-DB (K = 2.3 × 10⁴ M⁻¹) that was so selected as template. Cyclic voltammetry (CV) in homogeneous solution demonstrated the role of CoTAPP as catalyst in 2,4-DB reductive dechlorination. MIP was electropolymerized and electrochemically characterized by CV. The resulting polymer was then employed in the voltammetric detection of 2,4-DB at hundreds M concentration. A linear calibration curve was obtained in the concentration range 50–400 M (R = 0.9957). MIP showed a higher response than not-imprinted polymer (NIP), besides a good selectivity being able to reject a closely related compound (2,4-DP). The highest estimated ratio between MIP response to 2,4-DB and 2,4-DP (at the same concentration 600 M) was equal to 6.6.