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On-line molecularly imprinted solid phase extraction for the selective spectrophotometric determination of catechol
Authors:Eduardo Costa Figueiredo  Csar Ricardo Teixeira Tarley  Lauro Tatsuo Kubota  Susanne Rath  Marco Aurlio Zezzi Arruda
Institution:aUniversidade Estadual de Campinas, Institute of Chemistry, Department of Analytical Chemistry, P.O. Box 6154, 13084-970 Campinas, SP, Brazil;bUniversidade Federal de Alfenas, Departamento de Ciências Exatas, Rua Gabriel Monteiro da Silva, 714, 37170-000 Alfenas, MG, Brazil
Abstract:A molecularly imprinted polymer has been synthesized for a selective on-line catechol extraction, followed by its spectrophotometric determination in guarana powder, mate tea and tap water samples. A clean-up column, containing a methacrylic polymer + C18 solid phase, was also used in order to enhance selectivity. The imprinted polymer was prepared by bulk polymerization using catechol as template and 4-vinylpyridine as the functional monomer. Permanganate solution was used as spectrophotometric reagent, where Mn(VII) was reduced to Mn(II) by catechol in an acid medium, causing color loss, which was monitored at 528 nm. Physical (extraction flow rate, elution flow rate, coil length) and chemical (nature and concentration of the eluent, potassium permanganate concentration) variables were optimized, and the selectivity was appraised using three molecules (4-chloro-2-methylphenol, 2-cresol, 2-methoxyphenol) similar to catechol. These molecules did not present interference in 1:8, 1:10 and 1:10 (catechol/concomitant) proportions, respectively. The analytical calibration curve ranged from 3.0 up to 100 μmol L− 1 (r > 0.999; seven concentrations levels, n = 3) and the limits of detection (LOD) and quantification (LOQ) were 0.8 and 2.7 μmol L− 1, respectively. Precision, expressed as RSD, was of 3.0% (20 μmol L− 1, n = 10), and the analytical frequency was 15 h− 1. Accuracy was checked by the HPLC technique and the results did not present significant difference at 95% confidence levels according to the t test.
Keywords:Molecularly imprinted polymer  Spectrophotometry  Solid phase extraction  Catechol  Tea  Guarana  Tap water
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