Biomedical subjects

A Martin-Esteban

Publications and source records attributed to A Martin-Esteban.

4 recordsLinked to original sources

PubMed2004

Characterisation and quality assessment of binding sites on a propazine-imprinted polymer prepared by precipitation polymerisation.

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.

Binding Sites↗

PubMed2001

Molecular recognition in a propazine-imprinted polymer and its application to the determination of triazines in environmental samples.

An analytical methodology for the determination of triazines in environmental samples incorporating a molecularly imprinted solid-phase extraction (MISPE) process using a propazine-imprinted polymer was developed. Two different polymers were prepared using acetonitrile or toluene as porogen, and their optimum loading, washing, and elution conditions were established. Although both polymers were able to recognize several chlorotriazines (propazine, atrazine, simazine, desethylatrazine, and desisopropylatrazine), the polymer prepared in toluene showed the best performance and was also capable of recognizing a methylthiotriazine (prometryn). A binding study carried out in this polymer demonstrated that it possesses heterogeneous binding sites with different binding abilities. From this study, it was also concluded that desethylatrazine and desisopropylatrazine displace the other triazines at high concentrations, including the template molecule. The accuracy and selectivity of the MISPE process developed was verified using a certified reference material for drinking water containing atrazine and simazine among other commonly used pesticides. Finally, the MISPE procedure was successfully applied to the cleanup of drinking and groundwater, soil, and corn sample extracts, and the triazines were determined by micellar electrokinetic chromatography.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2001

Molecularly imprinted polymers: new molecular recognition materials for selective solid-phase extraction of organic compounds.

During the last few years molecularly imprinted polymers have appeared as new selective sorbents for solid-phase extraction of organic compounds in different samples. Molecular imprinting technology involves the preparation of a polymer with specific recognition sites for certain molecules. Once the polymer has been obtained, it can be used in solid-phase extraction protocols, where a careful selection of the most appropriate solvents to be used in the different steps (sample loading, washing and elution) is needed in order to extract the target analyte selectively. This review describes the state of the art of this methodology, including the preparation of imprinted polymers, a process description for molecularly imprinted solid-phase extraction, as well as more recent applications. It is concluded that molecularly imprinted solid-phase extraction is a powerful tool to selectively isolate certain analytes, and future advances are to be expected in order to widen the field of application.

Chromatography, Liquid↗

PubMed1997

Mixed immunosorbent for selective on-line trace enrichment and liquid chromatography of phenylurea herbicides in environmental waters.

An immunosorbent containing antiisoproturon and antichlortoluron antibodies immobilised on aldehyde-activated silica was employed for the on-line preconcentration and liquid chromatography-diode array detection of several phenylureas. The efficiency of the coupling of the immunosorbent to the liquid chromatographic system and the characteristics of the immunosorbent were evaluated. The on-line system allowed the selective trace enrichment of chlortoluron, isoproturon, metobromuron, linuron and chlorbromuron at the 0.05-0.5 microgram l-1 level in ground and river waters and provided detection limits in the range 0.01-0.03 microgram l-1 by percolating only 10 ml of water sample. The proposed method was validated by analysing freeze-dried tap water samples with a high content in pesticides of different chemical functionalities. The results obtained were compared with the mean value obtained in an interlaboratory exercise.

Chromatography, Liquid↗