Electrochemical detection of the toxic organohalide 2,4-DB using a Co-porphyrin based electrosynthesized molecularly imprinted polymer

The electrochemical synthesis of a metal complex based molecularly imprinted polymer (MIP) has been applied to the development of an electrochemical sensor for a chlorophenoxy carboxylic acid (4-(2,4-dichlorophenoxy)butyric acid (2,4-DB)) commonly used as pesticide. MIP has been electrosynthesized on a platinum electrode by using a Co-porphyrin (Co(III)tetrakis(o-aminophenyl) porphyrin) as functional monomer. The entrapment of the template in polymeric matrix after polymerization was verified by FT-IR experiments. Washing protocol has been investigated by studying the effect of different solvents as well as of the exposure time to washing mixture by XPS analysis. Under selected conditions almost the total amount of the withdrawn template was removed. An interaction mechanism between MIP and template was hypothesized on the basis of XPS data. The imprinting effect was verified by comparing electrochemical responses of MIP and not-imprinted polymer (NIP) tested by cyclic voltammetry between −0.1 and −1.7 V (vs Ag/Ag+ 0.1 M in ACN) and at a constant potential (−1.8 V vs Ag/Ag+ 0.1 M in ACN). In both cases MIP revealed an enhanced electrocatalytic activity towards 2,4-DB reduction. Amperometric MIP response revealed to be particularly satisfactory in terms of linear range (200 μM–2 mM), sensitivity (5.89 μA mM−1), reproducibility (RSD 17%) and time-stability. Moreover, MIP-based electrodes evidenced a good selectivity against both pesticides and structurally related compounds with a total removal of interference coming from chlorophenols.