A simple, rapid and sensitive electrochemical method using a molecularly imprinted poly-phenol polymer for the analysis of disulfoton in model and real samples is demonstrated. A computational approach to molecularly imprinted polymer design and screening is followed using density functional (B3LYP) and Semi-Empirical Parameterized Model number 3 (PM3) models. The selected phenol monomer is electrochemically polymerized by cyclic voltammetry at a glassy carbon working electrode in the presence of a disulfoton template. The subsequent molecularly imprinted polymer sensor exhibits an oxidation peak at 1.13 V vs. Ag/AgCl in cyclic voltammetry with excellent linearity (r 2 =0.9985) over the range 1-30 µM. The limit of detection for the DSN-MIP is 0.183 µM, compared to a limit of detection of 1.64 µM with cyclic voltammetry for the bare glassy carbon electrode. Intra-and inter-day assay precisions, expressed as relative standard deviation, are both found to be less than 7% overall. The developed molecularly imprinted polymer sensor is utilized to determine disulfoton in both spiked synthetic human plasma and human urine samples with recoveries ranging from 85.2% to 101.1%. The developed methods can be applied for measuring this toxicant in a real sample.
Coumaphos is an organophosphorus compound used as insecticide and frequently used by beekeepers for the management of parasitic mites. The most important metabolite, chlorferron (CFN), has been identified in biological samples and foodstuff. The need to quickly identify the presence of typical metabolites, as an indication of interaction with coumaphos has driven the need to produce a highly sensitive electrochemical method for chlorferron analysis, based on molecularly imprinting polymers (MIP) technology. It showed irreversible behaviour with mixed diffusion/adsorption-controlled reactions at the electrode surface. A monoelectronic mechanism of reaction for oxidation has also been suggested. The linear range observed was from 0.158 to 75 µM. Median precision in terms of %RSD around 3% was also observed. For DPV, the limit of detection (LOD) and the limit of quantitation (LOQ) for the CFN-MIP were 0.158 µM and 0.48 µM, respectively. The obtained median % recovery was around 98%. The results were also validated to reference values obtained using GC-MS. Urine and human synthetic plasma spiked with CFN were used to demonstrate the usability of the method in biological samples, showing the potential for biomonitoring. The developed imprinted sensor showed maximum signal change less than 16.8% when related metabolites or pesticide were added to the mix, suggesting high selectivity of the MIP sensor toward CFN molecules. The results from in vitro metabolism of CMP analysed also demonstrates the potential for detection and quantification of CFN in environmental samples. The newly developed CFN-MIP sensor offers similar LoDs than chromatographic methods with shorter analysis time.
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