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E Turiel

Publications and source records attributed to E Turiel.

18 recordsLinked to original sources
PubMed2006

Molecularly imprinted polymers for solid-phase extraction and solid-phase microextraction: recent developments and future trends.

Molecularly imprinted polymers (MIPs) are synthetic polymers having a predetermined selectivity for a given analyte, or group of structurally related compounds, that make them ideal materials to be used in separation processes. In this sense, during past years a huge amount of papers have been published dealing with the use of MIPs as sorbents in solid-phase extraction, namely molecularly imprinted solid-phase extraction (MISPE). Although the majority of these papers were restricted to describe the use of different templates for different applications, several attempts proposing new alternatives to minimize the inherent drawbacks of the preparation and use of MIPs (i.e. template bleeding, tedious synthesis procedure, etc.) have been reported. Thus, this paper does not pretend to be a collection of MISPE-related papers but to give an overview on the significant attempts carried out during recent years to improve the performance of MIPs in solid-phase extraction. In addition, the use of MIPs packed in high performance liquid chromatography (HPLC) columns for the direct injection of crude sample extracts and the preparation of imprinted fibres for solid-phase microextraction will be also discussed.

Combinatorial Chemistry Techniques↗
PubMed2006

Semi-covalent imprinted polymer using propazine methacrylate as template molecule for the clean-up of triazines in soil and vegetable samples.

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.

Food Contamination↗
PubMed2005

HPLC imprinted-stationary phase prepared by precipitation polymerisation for the determination of thiabendazole in fruit.

A molecularly imprinted polymer (MIP) tailored for the HPLC determination of the fungicide thiabendazole (TBZ) has been synthesised in one single preparative step by precipitation polymerisation in an acetonitrile/toluene co-solvent, using TBZ as template molecule, methacrylic acid as functional monomer and divinylbenzene-80 as crosslinker. The imprinted polymer particulates obtained were characterised by scanning electron microscopy and nitrogen sorption porosimetry. These analyses showed clearly that spherical polymer particulates (polymer microspheres) with narrow size distributions (average particle diameter approximately 3.5 microm) and well-developed pore structures had been produced. The imprinted microspheres were packed into a stainless steel HPLC column (50 x 4.6 mm id) and evaluated as an imprinted stationary phase. The imprinting effect was demonstrated clearly, i.e., the column was observed to bind TBZ selectively, and the effect of different chromatographic parameters (e.g., temperature, flow-rate and elution solvents) on TBZ retention/elution studied. Under optimised conditions, the TBZ-imprinted column was used for the HPLC-fluorescence (HPLC-F) determination of TBZ directly from orange (both whole fruit and juice), lemon, grape and strawberry extracts at low concentration levels in less than 15 min, without any need for a clean-up step in the analytical protocol.

Antinematodal Agents↗
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↗
PubMed2003

Molecularly imprinted polymers: towards highly selective stationary phases in liquid chromatography and capillary electrophoresis.

Molecularly imprinted polymers (MIPs) are synthetic polymers with a predetermined selectivity for a given analyte, or group of structurally related compounds, that make them ideal materials to be used in separation processes. In this sense, it is not surprising that the first applications of MIPs were as tailor-made chiral stationary phases in liquid chromatography. However, peak broadening and tailing, especially of the more retained enantiomers, were observed. Accordingly, this paper gives an overview of the attempts carried out during the recent years to improve the chromatographic performance of MIPs in liquid chromatography and capillary electrophoresis as well as the more recent applications. We conclude that MIPs are very promising materials to be used as selective stationary phases in chromatography although further developments are necessary in order to fully exploit their potential.

Binding Sites↗
PubMed2003

Clean-up of triazines in vegetable extracts by molecularly-imprinted solid-phase extraction using a propazine-imprinted polymer.

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.

Chromatography, High Pressure Liquid↗
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↗
PubMed2000

Trace-level determination of triazines and several degradation products in environmental waters by disk solid-phase extraction and micellar electrokinetic chromatography.

An analytical method combining disk solid-phase extraction with micellar electrokinetic chromatography has been developed for the determination of atrazine, simazine, hydroxyatrazine, deisopropylatrazine, deethylatrazine, propazine and prometryn in water samples. The influence of the buffer and sodium dodecyl sulfate (SDS) concentration, pH and organic modifier on the separation has been studied. Baseline separation of the seven triazines was achieved under the following conditions: 10 mM borate buffer, 60 mM SDS, 20% methanol and pH 9.2. C18-bonded silica and poly(styrene-divinylbenzene) (PS-DVB) disks were evaluated for solid-phase extraction of the selected pesticides (11 of water sample). Using two PS-DVB disks, quantitative recoveries were obtained for all pesticides tested. The method was successfully applied for the determination of the seven triazines in drinking and well water at the 0.1 microg l(-1) and 0.5 microg l(-1) concentration levels, respectively. The detection limits for these analytes using the proposed analytical method were within the 0.02-0.06 microg l(-1) range in drinking water and the 0.06-0.30 microg l(-1) range in well water.

Buffers↗
PubMed1995

Children's judgements about psychological harm in social context.

72 children, ages 6 to 11 years, were presented with a series of stories involving psychological harm (name-calling) in a game context. Situations were presented in which intentions, consequences, and game context were varied, along with order of story presentation. Comparison between acts of physical and psychological harm were also conducted. Although responses in some conditions were influenced by order of presentation, age differences were found in children's evaluations of agents' actions and recipients' reactions for psychological harm in game contexts. Younger children were more likely to ignore intentions and consequences or the recipient's perspective and to focus on contextual features (e.g. game rules). Older children were more likely to base their evaluations on intentions, or both intentions and consequences, and to take into account the recipient's perspective. Game context interacted differentially with psychological and physical harm at all ages. Evaluations of acts of physical harm were more likely than acts of psychological harm to be transformed by game context.

Affect↗
PubMed1991

Judging social issues: difficulties, inconsistencies, and consistencies.

The three studies reported in this Monograph examine high school and college students' reasoning about the issues of abortion, homosexuality, pornography, and incest. The studies stemmed from previous research on reasoning in the "prototypical" moral, social conventional, and personal domains. We postulated that abortion, homosexuality, pornography, and incest are nonprototypical issues. We expected that reasoning about nonprototypical and prototypical issues would differ and that reasoning about nonprototypical issues would be inconsistent and involve ambiguities in informational assumptions. Two groups were preselected in Study 1, those who negatively and those who positively evaluated the nonprototypical issues. Assessments were made of criterion judgments (evaluations, rule contingency, and generalizability) and justifications regarding moral, personal, and nonprototypical issues. The groups differed in judgments about the nonprototypical issues but not the moral issues. Both groups gave noncontigent and generalized judgments about moral issues, with justifications of justice and rights. Subjects who evaluated nonprototypical acts negatively used varied and often inconsistent configurations of criterion judgments. Responses coded for general reasoning types often entailed juxtapositions of prescriptive judgments and assertions of personal choice. Subjects who evaluated nonprototypical acts positively judged that they should be legal and nongeneralized and gave justifications based on personal choice. Using similar procedures, Study 2 was conducted with practicing Catholics attending parochial high schools. The findings paralleled those of Study 1, including a split among subjects in their evaluations of the nonprototypical issues. The results suggested a bidirectional relation between individual judgments and group positions. The findings of Studies 1 and 2 suggested that variations in evaluations and judgments about the nonprototypical issues were associated with variations in ambiguously held informational assumptions. Study 3 examined the role of such informational assumptions. It was found that assumptions associated with judgments about abortion and homosexuality were ambiguous and inconsistently applied. Thus, we propose that ambiguity around assumptions is a central component of the nonprototypicality of these issues.

Abortion, Legal↗
PubMedDate not supplied

Social life in cultures: judgements, conflict, and subversion.

We present a developmentally grounded perspective on the study of social life in cultures that examines the sources of the coexistence of sociability and opposition, harmony and conflict, acceptance and critique. The coexistence of these elements, it is proposed, is systematically connected both to the development of distinct domains of thought and to the dynamics of participation in more and less hierarchical social relationships in society.

Conflict, Psychological↗