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Papers by ENCARNACIÓN RODRÍGUEZ GONZALO

Research paper thumbnail of Acid-base behaviour of the herbicide Pyrazon : a spectroscopic and polarographic study

Analusis, 1991

Infrared spectroscopic studies revealed that the herbicide Pyrazon (5-amino-chloro-2-phenyl-3(2H)... more Infrared spectroscopic studies revealed that the herbicide Pyrazon (5-amino-chloro-2-phenyl-3(2H)-pyridazinone) is in acid-base equilibrium with a form produced by acid hydrolysis of the >C=N- bond, which in turn involves the reversible opening of the pyridazine ring. The acid-base constant of this equilibrium could not be calculated by spectroscopic or potentiometric methods; the polarographic dissociation constant, pK' a , could only be determined by polarographic studies in different buffers

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Research paper thumbnail of Adsorption of parathion and paraoxon by modified montmorillonites

Toxicological & Environmental Chemistry, 1993

Montmorillonites modified with tetradecyltrimethylammonium and trimethylphenyl ammonium and the h... more Montmorillonites modified with tetradecyltrimethylammonium and trimethylphenyl ammonium and the hydroxy‐Al polymer were studied as sorbents for organophosphorus pesticides parathion and paraoxon in aqueous media. Sorptive characteristics of modified‐clays depend on their organic carbon content and the hydrophobic nature of the pesticide. Hydroxy‐Al‐montmorillonite showed a weak capacity for adsorption of both pesticides. In contrast, tetradecyltrimethylammonium‐montmorillonite appears to be an effective sorbent for removing hydrophobic pesticides from water and this fact can be applied for contamination prevention or decontamination of sediments and waters.

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Research paper thumbnail of Determination of the fungicides folpet, captan and captafol by cloud-point preconcentration and high-performance liquid chromatography with electrochemical detection

Journal of Chromatography A, 1996

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Research paper thumbnail of Determination of acephate by liquid chromatography in the presence of aqueous soil extracts

Journal of Chromatography A, 1991

ABSTRACT A liquid chromatographic method has been developed for the determination of acephate in ... more ABSTRACT A liquid chromatographic method has been developed for the determination of acephate in aqueous extracts of agriculture soils. Aqueous extracts of spiked soil samples were used. The lower detection limit was 1 μg/ml; the relative standard deviation for repeatability (R.S.D.) based on peak area measurement ranged from 0.2 to 4.5%. Recoveries from spiked samples ranged from 93.6 to 104.3%. The method used a C18 reversed-phase column, a mobile phase of 5% (v/v) methanol-water and UV detection at 215 nm. The application of the proposed method to the study of the adsorption of acephate in aqueous medium by a selected group of soils yielded satisfactory results.

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Research paper thumbnail of Membrane extraction-preconcentration cell coupled on-line to flow-injection and liquid chromatographic systems. Determination of triazines in oils

Analytica Chimica Acta, 1995

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Research paper thumbnail of Determination of triazine herbicides in water by micellar electrokinetic capillary chromatography

Capillary electrophoresis was applied to the analysis of a mixture of triazine herbicides of envi... more Capillary electrophoresis was applied to the analysis of a mixture of triazine herbicides of environmental interest. Micellar electrokinetic capillary chromatography (MECC) proved to be satisfactory for the separation of triazines, providing high efficiency in short analysis times. Several electrophoretic parameters were investigated: injection conditions, pH and buffer concentration, surfactant concentration and applied voltage. The optimized MECC method was applied to the determination of these compounds in water samples; using a solid-phase concentration step, herbicide concentrations lower than 0.2 ng/ml can be measured, the relative standard deviations being about 20%.

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Research paper thumbnail of Determination of triazines in surface waters by membrane separation coupled on-line to a flow-injection system and partial least squares regression

Analytica Chimica Acta, 1996

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Research paper thumbnail of Electroanalytical study of the pesticide guthion

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, Apr 1, 1988

ABSTRACT

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Research paper thumbnail of Determination of the fungicides folpet, captan and captafol by cloud-point preconcentration and high-performance liquid chromatography with electrochemical detection

Journal of Chromatography A, 1996

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Research paper thumbnail of Sensitive method for the determination of organophosphorus pesticides in fruits and surface waters by high-performance liquid chromatography with ultraviolet …

… of Chromatography A, 1992

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Research paper thumbnail of Rapid and reliable analysis of underivatized amino acids in urine using tandem mass spectrometry

Microchemical Journal

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Research paper thumbnail of Development of a fast and reliable methodology for the determination of polyamines in urine by using a guard column as a low-resolution fractioning step prior to mass spectrometry. Comparison with flow injection-mass spectrometry analysis

Microchemical Journal

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Research paper thumbnail of Determination of leucine and isoleucine/allo-isoleucine by electrospray ionization-tandem mass spectrometry and partial least square regression: Application to saliva samples

Talanta

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Research paper thumbnail of Analysis of Isoflavones in Foods

Comprehensive Reviews in Food Science and Food Safety

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Research paper thumbnail of Development of a screening and confirmatory method for the analysis of polar endogenous compounds in saliva based on a liquid chromatographic-tandem mass spectrometric system

Journal of Chromatography A

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Research paper thumbnail of Determination of nucleosides and nucleotides in food samples by using liquid chromatography and capillary electrophoresis

TrAC Trends in Analytical Chemistry

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Research paper thumbnail of Capillary electrophoresis coupled to mass spectrometry employing hexafluoro-2-propanol for the determination of nucleosides and nucleotide mono-, di- and tri-phosphates in baby foods

Food Chemistry

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Research paper thumbnail of Anthelmintic Benzimidazoles in Eggs

Egg Innovations and Strategies for Improvements, 2017

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Research paper thumbnail of Determination of nucleosides and nucleotides in baby foods by hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of hydrophilic ion-pairing reagents

Food Chemistry, 2016

In this work we propose a rapid and efficient method for the joint determination of nucleosides a... more In this work we propose a rapid and efficient method for the joint determination of nucleosides and nucleotides in dairy and non-dairy baby foods based on hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of diethylammonium (DEA) as a hydrophilic ion-pairing reagent (IP-HILIC-MS/MS). Sample treatment of the baby food included dilution with water and centrifugal ultrafiltration (CUF) with an additional washing step that notably improved the global performance of the process. Later dilution of the extract with acetonitrile allowed adequate separation in the HILIC system. With the proposed treatment, we obtained extraction recoveries higher than 80% and, additionally, no matrix effects were observed. The CUF-IP-HILIC-MS/MS method was validated according to the 2002/657/EC decision and was used for the quantification of nucleotides and nucleosides in sixteen samples of commercial baby foods.

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Research paper thumbnail of Evaluation of surface- and ground-water pollution due to herbicides in agricultural areas of Zamora and Salamanca (Spain)

Journal of Chromatography a, Mar 1, 2000

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Research paper thumbnail of Acid-base behaviour of the herbicide Pyrazon : a spectroscopic and polarographic study

Analusis, 1991

Infrared spectroscopic studies revealed that the herbicide Pyrazon (5-amino-chloro-2-phenyl-3(2H)... more Infrared spectroscopic studies revealed that the herbicide Pyrazon (5-amino-chloro-2-phenyl-3(2H)-pyridazinone) is in acid-base equilibrium with a form produced by acid hydrolysis of the >C=N- bond, which in turn involves the reversible opening of the pyridazine ring. The acid-base constant of this equilibrium could not be calculated by spectroscopic or potentiometric methods; the polarographic dissociation constant, pK' a , could only be determined by polarographic studies in different buffers

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Adsorption of parathion and paraoxon by modified montmorillonites

Toxicological & Environmental Chemistry, 1993

Montmorillonites modified with tetradecyltrimethylammonium and trimethylphenyl ammonium and the h... more Montmorillonites modified with tetradecyltrimethylammonium and trimethylphenyl ammonium and the hydroxy‐Al polymer were studied as sorbents for organophosphorus pesticides parathion and paraoxon in aqueous media. Sorptive characteristics of modified‐clays depend on their organic carbon content and the hydrophobic nature of the pesticide. Hydroxy‐Al‐montmorillonite showed a weak capacity for adsorption of both pesticides. In contrast, tetradecyltrimethylammonium‐montmorillonite appears to be an effective sorbent for removing hydrophobic pesticides from water and this fact can be applied for contamination prevention or decontamination of sediments and waters.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of the fungicides folpet, captan and captafol by cloud-point preconcentration and high-performance liquid chromatography with electrochemical detection

Journal of Chromatography A, 1996

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of acephate by liquid chromatography in the presence of aqueous soil extracts

Journal of Chromatography A, 1991

ABSTRACT A liquid chromatographic method has been developed for the determination of acephate in ... more ABSTRACT A liquid chromatographic method has been developed for the determination of acephate in aqueous extracts of agriculture soils. Aqueous extracts of spiked soil samples were used. The lower detection limit was 1 μg/ml; the relative standard deviation for repeatability (R.S.D.) based on peak area measurement ranged from 0.2 to 4.5%. Recoveries from spiked samples ranged from 93.6 to 104.3%. The method used a C18 reversed-phase column, a mobile phase of 5% (v/v) methanol-water and UV detection at 215 nm. The application of the proposed method to the study of the adsorption of acephate in aqueous medium by a selected group of soils yielded satisfactory results.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Membrane extraction-preconcentration cell coupled on-line to flow-injection and liquid chromatographic systems. Determination of triazines in oils

Analytica Chimica Acta, 1995

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of triazine herbicides in water by micellar electrokinetic capillary chromatography

Capillary electrophoresis was applied to the analysis of a mixture of triazine herbicides of envi... more Capillary electrophoresis was applied to the analysis of a mixture of triazine herbicides of environmental interest. Micellar electrokinetic capillary chromatography (MECC) proved to be satisfactory for the separation of triazines, providing high efficiency in short analysis times. Several electrophoretic parameters were investigated: injection conditions, pH and buffer concentration, surfactant concentration and applied voltage. The optimized MECC method was applied to the determination of these compounds in water samples; using a solid-phase concentration step, herbicide concentrations lower than 0.2 ng/ml can be measured, the relative standard deviations being about 20%.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of triazines in surface waters by membrane separation coupled on-line to a flow-injection system and partial least squares regression

Analytica Chimica Acta, 1996

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Electroanalytical study of the pesticide guthion

Journal of Electroanalytical Chemistry and Interfacial Electrochemistry, Apr 1, 1988

ABSTRACT

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of the fungicides folpet, captan and captafol by cloud-point preconcentration and high-performance liquid chromatography with electrochemical detection

Journal of Chromatography A, 1996

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Sensitive method for the determination of organophosphorus pesticides in fruits and surface waters by high-performance liquid chromatography with ultraviolet …

… of Chromatography A, 1992

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Rapid and reliable analysis of underivatized amino acids in urine using tandem mass spectrometry

Microchemical Journal

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Development of a fast and reliable methodology for the determination of polyamines in urine by using a guard column as a low-resolution fractioning step prior to mass spectrometry. Comparison with flow injection-mass spectrometry analysis

Microchemical Journal

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of leucine and isoleucine/allo-isoleucine by electrospray ionization-tandem mass spectrometry and partial least square regression: Application to saliva samples

Talanta

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Analysis of Isoflavones in Foods

Comprehensive Reviews in Food Science and Food Safety

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Development of a screening and confirmatory method for the analysis of polar endogenous compounds in saliva based on a liquid chromatographic-tandem mass spectrometric system

Journal of Chromatography A

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of nucleosides and nucleotides in food samples by using liquid chromatography and capillary electrophoresis

TrAC Trends in Analytical Chemistry

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Capillary electrophoresis coupled to mass spectrometry employing hexafluoro-2-propanol for the determination of nucleosides and nucleotide mono-, di- and tri-phosphates in baby foods

Food Chemistry

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Anthelmintic Benzimidazoles in Eggs

Egg Innovations and Strategies for Improvements, 2017

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Determination of nucleosides and nucleotides in baby foods by hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of hydrophilic ion-pairing reagents

Food Chemistry, 2016

In this work we propose a rapid and efficient method for the joint determination of nucleosides a... more In this work we propose a rapid and efficient method for the joint determination of nucleosides and nucleotides in dairy and non-dairy baby foods based on hydrophilic interaction chromatography coupled to tandem mass spectrometry in the presence of diethylammonium (DEA) as a hydrophilic ion-pairing reagent (IP-HILIC-MS/MS). Sample treatment of the baby food included dilution with water and centrifugal ultrafiltration (CUF) with an additional washing step that notably improved the global performance of the process. Later dilution of the extract with acetonitrile allowed adequate separation in the HILIC system. With the proposed treatment, we obtained extraction recoveries higher than 80% and, additionally, no matrix effects were observed. The CUF-IP-HILIC-MS/MS method was validated according to the 2002/657/EC decision and was used for the quantification of nucleotides and nucleosides in sixteen samples of commercial baby foods.

Bookmarks Related papers MentionsView impact

Research paper thumbnail of Evaluation of surface- and ground-water pollution due to herbicides in agricultural areas of Zamora and Salamanca (Spain)

Journal of Chromatography a, Mar 1, 2000

Bookmarks Related papers MentionsView impact

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