title: Molecularly imprinted probe for solid-phase extraction of hippuric and 4-methylhippuric acids directly from human urine samples followed by MEKC analysis.
abstract: Hippuric acid (HA) and 4-methylhippuric acid (4-MHA) are metabolites as well as biological indicators for toluene and xylenes, respectively, and their determination in urine samples is very important, in order to monitor the occupational exposition to these solvents, ensuring a safe working environment. Thus, this paper describes the synthesis and characterization of a probe impregnated with molecularly imprinted polymers (MIPs) for the solid-phase extraction of HA and 4-MHA directly from untreated urine samples followed by micellar electrokinetic chromatography (MEKC) analyses. The MIP probe selectivity was compared to the non-imprinted polymer probe. The MEKC separations were carried out in 50 mmol/L sodium tetraborate pH 10.0/0.5 mmol/L cetyltrimethylammonium bromide aqueous solution, with a constant voltage of -15 kV. The system variables were optimized to provide ideal conditions for the extraction and desorption of the analytes, as well as for the MEKC analyses. The method was linear from 0.5 to 5.0 g/L for both analytes, with correlation coefficients > 0.994. Precisions and accuracies, expressed as relative standard deviation and relative error, were < 20.0 and within -15.4 to 16.6%, respectively, in accordance with the United States Food and Drug Administration recommendation. The MIP probe has proven to be simple, cheap, resistant, and synthetically reproducible, being successfully used to analyze both HA and 4-MHA from real samples.
authors.affiliation: Faculty of Pharmaceutical Sciences, Federal University of Alfenas, Alfenas, Brazil.
authors.forename: Carolina Nasser
authors.initials: CN
authors.lastname: Boscari
authors.affiliation: Faculty of Pharmaceutical Sciences, Federal University of Alfenas, Alfenas, Brazil.
authors.forename: Giovanna Rodrigues
authors.initials: GR
authors.lastname: Mazzuia
authors.affiliation: Institute of Exact Sciences, Federal University of Alfenas, Alfenas, Brazil.
authors.forename: Célio
authors.initials: C
authors.lastname: Wisniewski
authors.affiliation: Department of Natural Sciences, Federal University of São João del-Rei, São João del-Rei, Brazil.
authors.forename: Keyller Bastos
authors.initials: KB
authors.lastname: Borges
authors.affiliation: Faculty of Pharmaceutical Sciences, Federal University of Alfenas, Alfenas, Brazil.
authors.forename: Eduardo Costa
authors.initials: EC
authors.lastname: Figueiredo
mesh_terms: D020374:Chromatography, Micellar Electrokinetic Capillary / Q000379:methods*; D006626:Hippurates / Q000652:urine*; D006801:Humans; D057230:Limit of Detection; D016014:Linear Models; D054802:Molecular Imprinting / Q000379:methods*; D015203:Reproducibility of Results; D052616:Solid Phase Extraction / Q000379:methods*
chemical_list: D006626:Hippurates; C031422:4-methylhippuric acid; C030514:hippuric acid
keywords: Capillary electrophoresis; Hippuric acid; Methylhippuric acid; Molecularly imprinted polymer; Urine