Abstract: In this work, the suitability of the combination of molecular imprinting and capillary electrochromatography (MIP-CEC) to be used as powerful
tool in environmental or food analysis has been for the first time studied and successfully demonstrated. A molecularly imprinted monolith (MIM)
has been synthesised and evaluated as stationary phase for the selective determination of the fungicide thiabendazole (TBZ) in citrus samples by
non-aqueous capillary electrochromatography. The influence of the mobile phase composition, the voltage of the power supply and the separation
temperature on the recognition of TBZ by the imprinted polymer has been evaluated, and the imprint effect in the MIM was clearly demonstrated.
Once optimum recognition conditions were established, other variables affecting mechanical properties and chromatographic performance of MIM
were adjusted using computational approach. The high selectivity achieved by the MIP-CEC developed procedure allowed unambiguous detection
and quantification of TBZ in citrus samples by direct injection of the crude sample extracts, without any previous clean-up, in less than 6 min. The
developed method was properly validated and the calculated detection limits were bellow the established maximum residue limits (MRLs), clearly
demonstrating the suitability of the method to be used for the control of the selected fungicide.
Abstract: A semi-covalent imprinted polymer was prepared by precipitation polymerisation using propazine methacrylate as template molecule, ethylene
glycol dimethacrylate as cross-linker and toluene as porogen. After removal of propazine by basic hydrolysis of the covalent bond, the optimum
loading, washing and elution conditions for the solid-phase extraction of the selected triazines were established. The binding sites present in
the polymeric matrix were characterised by fitting the experimental results of several rebinding studies to the Langmuir–Freundlich isotherm.
Subsequently, an analytical methodology based on molecularly imprinted solid-phase extraction (MISPE) was developed for the determination of
several triazinic herbicides in soil and vegetable samples. Following this procedure, a good degree of clean-up of the sample extracts was easily
achieved, allowing the HPLC-UV determination of selected triazines in complex samples at low concentration levels.
Abstract: In this paper, the Langmuir–Freundlich isotherm (LF) is used to characterise a propazine-imprinted polymer obtained by precipitation
polymerisation (MIP-P). Different rebinding studies were carried out allowing to explain the different interactions taking place between
the molecularly imprinted polymer and six triazinic herbicides (desisopropylatrazine, desethylatrazine, simazine, atrazine, propazine and
prometryn). The LF fitting parameters obtained (total number of binding sites, heterogeneity index and mean binding affinity) were compared
to those obtained in a previous work for a propazine-imprinted polymer prepared by bulk polymerisation (MIP-B). From that study, it was
concluded that precipitation polymerisation yielded polymers with a more homogeneous binding site distribution and higher affinity constants.
Notes: Times Cited: 2
ABSTRACT of the paper JOURNAL OF CHROMATOGRAPHY B (2004) 802: 347-353
Abstract: In this paper, the Langmuir–Freundlich isotherm (LF) is used to characterise a propazine-imprinted polymer obtained by precipitation
polymerisation (MIP-P). Different rebinding studies were carried out allowing to explain the different interactions taking place between
the molecularly imprinted polymer and six triazinic herbicides (desisopropylatrazine, desethylatrazine, simazine, atrazine, propazine and
prometryn). The LF fitting parameters obtained (total number of binding sites, heterogeneity index and mean binding affinity) were compared
to those obtained in a previous work for a propazine-imprinted polymer prepared by bulk polymerisation (MIP-B). From that study, it was
concluded that precipitation polymerisation yielded polymers with a more homogeneous binding site distribution and higher affinity constants.
Abstract: An analytical methodology based on a molecularly imprinted solid-phase extraction (MISPE) procedure was developed for the determination of several triazines (atrazine, simazine, desethylatrazine (DEA), desisopropylatrazine (DIA), and propazine) in vegetable samples. A methacrylic acid-based imprinted polymer was prepared by precipitation polymerisation using propazine as template and toluene as porogen. After removal of the template by Soxhlet extraction, the optimum loading, washing, and elution conditions for MISPE of the selected triazines were established. The optimised MISPE procedure was applied to the extraction of the selected triazines in pea, potato, and corn sample extracts and a high degree of clean-up was obtained. However, some remaining interferences, non-specifically and strongly bound to the polymeric matrix, appeared in the chromatogram, preventing quantification of DIA in potatoes and DIA, DEA, and propazine in corn samples. Thus, a new clean-up protocol based on the use of a non-imprinted polymer for removal of these interferences prior to the MISPE step was developed. By following the new two-step MISPE procedure, the matrix compounds were almost completely removed, allowing the determination of all the triazines selected at concentration levels below the established maximum residue limits, making the developed procedure suitable for monitoring these analytes in vegetable samples.