Molecularly-imprinted solid phase extraction of catechol from aqueous effluents for its selective determination by differential pulse voltammetry

A polymeric sorbent based on molecular imprinting technology has been synthesized and applied to selectively extract catechol from water samples with subsequent determination by differential pulse voltammetry (DPV). The non-covalent polymer was prepared by bulk polymerization using catechol and 4-vinylpyridine as template and monomer, respectively. The effect of the flow and chemical variables associated to the performance of the solid phase extraction procedure was investigated and optimized using a 25−1 fractional factorial design as well as Doehlert design. A study of selectivity was carried out percolating a standard aqueous solution, which contained a mixture of catechol and five phenolic compounds (4-chloro-2-methoxyphenol, 4-aminophenol, 2-cresol, 2-methoxyphenol and 4-chloro-2-metoxyphenol) through the polymer packed into a cartridge followed by the elution with methanol/acetic acid (4:1, v/v) solution. Differential pulse voltammograms obtained from the eluted solution indicated that all compounds were retained on the sorbent since an overlapped peak was verified, showing the necessity to include a washing step. For this task, methanol, tetrahydrofuran, acetonitrile, dichoromethane and chloroform were checked as washing solvent, in which chloroform was able to establish the specific interaction between catechol and those sites of molecularly-imprinted polymers (MIP). Recovery higher than 95% was obtained for extraction of catechol even in the presence of structurally similar phenolic compounds. The procedure was further applied for catechol determination in aqueous effluent from paper mill industry and river water.