Biomedical subjects

D Barceló

Publications and source records attributed to D Barceló.

At least 91 records · Page 5Linked to original sources

PubMed1999

Simultaneous determination of antifouling herbicides in marina water samples by on-line solid-phase extraction followed by liquid chromatography-mass spectrometry.

Solid-phase extraction (SPE) coupled on-line with either liquid chromatography-diode array detection (LC-DAD) or liquid chromatography-atmospheric pressure chemical ionization mass spectrometry was applied to the simultaneous analysis of several antifouling herbicides such as diuron, TCMTB (2-thiocyanomethylthiobenzothiazole), Irgarol and chlorothalonil in seawater samples. SPE was carried out on polymeric cartridges (PLRP-s) after the percolation of 100 ml of seawater sample, with recoveries ranging from 96 to 111% for the antifouling compounds. LC-MS detection was used in negative and positive ion mode. In positive ion mode, additional structural information for diuron and Irgarol was obtained by increasing the fragmentor voltage, thus permitting the unequivocal identification of these compounds in environmental waters. Method detection limits were in the range of 0.005 microg/l. This methodology was also compared to LC-DAD in terms of selectivity and sensitivity. Finally, the method was evaluated for the analysis of environmental seawater samples, from the Ebre Delta area and Masnou marina, in Catalonia (Spain).

Chromatography, Liquid↗

PubMed1999

On-line solid-phase extraction-ion-pair liquid chromatography-electrospray mass spectrometry for the trace determination of naphthalene monosulphonates in water.

This paper presents an HPLC-MS method for the fully automated determination of a group of naphthalene monosulphonates in environmental water samples. The analytical procedure consisted of on-line ion-pair solid-phase extraction using a PLRP-S precolumn and ion-pair LC separation with triethylamine as ion-pair reagent in both cases. A mass spectrometric detector, coupled to LC through an electrospray interface and operated in negative ion mode, was used. Diagnostic ions usually corresponded to [SO3]- and/or [M-SO2H]- together with [M-H] and/or [M-2H+Na]-. The method was applied to the trace determination of several sulphonates present in tap water, seawater and water from the Ebro river. The analytes were determined at a concentration level between 0.05 and 1 microg l(-1) under selected ion monitoring acquisition by preconcentrating just 15 ml of sample. Naphthalene-1-sulphonate and naphthalene-2-sulphonate were identified and quantified in one of the samples of seawater.

Chromatography, High Pressure Liquid↗

PubMed1999

Double-disk solid-phase extraction: simultaneous cleanup and trace enrichment of herbicides and metabolites from environmental samples.

Phenylurea and triazine herbicides, including some metabolites, were isolated from water and soil extracts by solid-phase extraction using a layered system of two extraction disks, a method called double-disk solid-phase extraction. The first disk consisted of strong anion exchange (SAX) of 10-micron styrene divinylbenzene (SDB) particles embedded in Teflon, and the second disk was a C18 disk of 10-micron particles also embedded in Teflon. A volume of 500 mL of water or aqueous soil extract is passed through the layered system with the SAX disk first. The purpose of the SAX disk is to remove the humic and fulvic acids from the water or aqueous soil extract by ion exchange through their carboxyl groups. Even during methanol elution of herbicides, the humic substances remain bound to the SAX disk with > 85% retention. Elution with methanol results in more than 90% recovery of the herbicides from the layered extraction disks. Removal of the humic and fulvic acids results in greater sensitivity for diode array detection quantitation (0.05 micrograms/L for herbicides) by substantially reducing the absorbance of the humic peak on the LC chromatogram. The herbicides adsorb to the SAX disk either through hydrogen bonding to the anion-exchange sites or by hydrophobic interaction with the SDB surface of the anion-exchange disk. The method was tested for the analysis of natural water samples from the Mississippi Embayment, a cotton-growing area of the southeastern United States.

Chromatography, High Pressure Liquid↗

PubMed1999

Comparative studies of the leachate of an industrial landfill by gas chromatography-mass spectrometry, liquid chromatography-nuclear magnetic resonance and liquid chromatography-mass spectrometry.

Nowadays, the need to have a realistic characterization of industrial effluents in the environment has become more and more recognized. A palette of different analytical methods both for sample extraction and instrumental analysis are available today, some older, others introduced more recently. The aim of this research is to compare a number of these techniques. To do this we studied a real leachate from an industrial landfill and carried out chemical analyses for organic pollutants, using different extraction methods based on solid-phase extraction and solid-phase microextraction and different instrumental techniques such as GC-MS, LC-MS, NMR and LC-NMR. Results show the performances of the different techniques, which are complementary.

Chromatography, Liquid↗

PubMed1998

Isolation of priority polycyclic aromatic hydrocarbons from natural sediments and sludge reference materials by an anti-fluorene immunosorbent followed by liquid chromatography and diode array detection.

The selective isolation of PAHs from complex environmental mixtures was accomplished by means of a new methodology based on antigen--antibody interactions. This method consists on the extraction of PAHs from water samples onto an anti-fluorene immunosorbent (IS) followed by liquid chromatography with diode array detection. Environmental sediments and a sludge reference material containing PAHs were analyzed using this methodology in order to validate the performance of the IS for the cleanup procedure of such materials. Sediments were extracted by sonication with dichloromethane/methanol (2:1), and the extracts were brought to a volume of 100 mL of water in order to perform the extraction with the anti-fluorene IS. The reliability of the cleanup achieved by the IS was well demonstrated in the analysis of sediment and sludge complex samples containing the priority PAHs established by the U.S. EPA at concentrations varying from 56 micrograms/kg to 26 mg/kg. Results were compared to those obtained with conventional cleanup procedures showing a better selectivity for PAHs. The chromatograms presented a clear baseline allowing the determination and quantification of PAHs at the ppb level. Using immunosorbents, extraction, trace enrichment, and cleanup were accomplished in only one step.

Chromatography, Liquid↗

PubMed1998

Validation of an immunoassay method for the determination of traces of carbaryl in vegetable and fruit extracts by liquid chromatography with photodiode array and mass spectrometric detection.

A competitive enzyme-linked immunosorbent assay (ELISA) method for carbaryl quantitation in crop extracts was validated by liquid chromatography (LC) with diode array detection (DAD). For this purpose, six crops (banana, carrot, green bean, orange, peach and potato) were chosen for recovery and reproducibility studies. The general sample preparation included extraction with methanol followed by liquid-liquid partitioning and clean-up on Celite-charcoal adsorbent column of the vegetable extracts. ELISA samples consisted of a diluted LC extract in assay phosphate buffer (pH 7.5). The potential effect of methanol in these samples was evaluated. It was observed that a maximum content of 10% methanol present in the assay buffer could be tolerated without expressive losses in the ELISA performance. Under these conditions, a IC50 approximately 1.48 micrograms l-1 was obtained. A minimum matrix effect with a 1:50 dilution of the methanolic extracts in assay buffer was noticed, except for green bean samples that inhibited completely the assay. For the vegetable extracts, the ELISA sensitivities varied from 3.9 to 5.7 micrograms l-1, and good recoveries (82-96%) with R.S.D.s ranging from 5.7 to 12.1% were found. An excellent correlation between the LC-DAD and ELISA techniques was obtained. The confirmation of the carbaryl in less concentrated samples was achieved by LC-mass spectrometry interfaced with atmospheric pressure chemical ionisation. The [M + H]+ = 202 and [M + H-57]+ = 145 ions, equivalent to the protonated molecular and 1-naphthol ions, respectively, were used to carbaryl identification in these samples.

Brazil↗

PubMed1998

Photodegradation and stability of chlorothalonil in water studied by solid-phase disk extraction, followed by gas chromatographic techniques.

Photodegradation of chlorothalonil was studied in deionized and ground water with sunlight and Suntest apparatus, with and without FeCl3/H2O2 and TiO2/H2O2. After irradiation of the water samples spiked at 28-100 micrograms/l of chlorothalonil, the water solutions were preconcentrated using solid-phase disk extraction with C18 and analyzed by gas chromatography-electron capture and gas chromatography-mass spectrometric detection. The degradation products identified by GC-MS were: trichloro-1,3-dicyanobenzene, dichloro-1,3-dicyanobenzene and chloro-1,3-dicyanobenzene. The degradation kinetics followed a first order reaction and the R.S.D. of rate constants, for n = 3, varied from 2 to 14%. Halflives varied between 0.7 and 101 h. The stability of chlorothalonil on C18 Empore disks was also investigated at 20 degrees C, 4 degrees C and -20 degrees C for periods of up to 3 months. Chlorothalonil was not degraded on C18 Empore disks.

Chlorides↗

PubMed1998

Analysis and degradation study of glyphosate and of aminomethylphosphonic acid in natural waters by means of polymeric and ion-exchange solid-phase extraction columns followed by ion chromatography-post-column derivatization with fluorescence detection.

The quantitative trace determination of glyphosate and its major metabolite, aminophosphonic acid (AMPA) in natural waters was achieved by means of ion-exchange chromatography. Fifty ml of natural water sample was preconcentrated by a two-step procedure: first the sample was percolated through a polymeric cartridge, LiChrolut EN, then through an anion-exchange column mechanism, and finally analyzed by ion-exchange chromatography followed by post-column reaction coupled to a fluorimetric detector. Linear calibration graphs were obtained between 5 and 200 micrograms l-1. Limits of detection ranged from 2 micrograms l-1 of glyphosate and 4 micrograms l-1 of AMPA. A study of the degradation of glyphosate in environmental waters under characteristic conditions was carried out to figure out the main degradation pathways of this compound. Half-lives of glyphosate varied from 60 h for ground water samples exposed to sunlight to 770 h for those stored under dark conditions.

Chromatography, Ion Exchange↗

PubMed1998

Comparison of various sample handling and analytical procedures for the monitoring of pesticides and metabolites in ground waters.

Various sample handling techniques such as liquid-liquid extraction off-line and on-line, solid-phase extraction followed by either gas chromatography (GC) with electron-capture, flame photometric or mass spectrometric detection, or liquid chromatography (LC) with diode array detection were applied in the determination of a selected group of insecticides and fungicides in ground water samples at sub-micrograms/l levels. An evaluation of the advantages and drawbacks in the application of the proposed methodologies for water monitoring studies is discussed. For the selected group of pesticides studied, off-line C18 or polymeric cartridges followed by GC-MS using an ion trap analyzer have been revealed as the more powerful technique. But very polar compounds such as methamidophos or acephate have not been recovered with this procedure. On the contrary, on-line C18 LC-DAD offered a few drawbacks for the trace determination of a large group of pesticides as a consequence of many important interferences in the chromatographic traces. Other techniques evaluated were LC-MS and GC-MS using a quadrupole analyzer, which offered complementary information and were useful for a limited range of analytes. An interlaboratory study was performed using all the methodologies evaluated in this work and the results obtained showed a good agreement between all the applied techniques. The various methodologies were for a ground water pilot survey study in Almeria (Spain). Endosulfan was the most ubiquitous pesticide detected in this area.

Chromatography, Gas↗

PubMed1998

Influence of the hapten design on the development of a competitive ELISA for the determination of the antifouling agent Irgarol 1051 at trace levels.

Enzyme-linked immunosorbent assays (ELISAs) with a high detectability have been developed for determination of the antifouling agent Irgarol 1051. The features of the resulting assays have been rationalized by using molecular mechanic calculations (MM2+) to correlate the chemical structure of different immunizing haptens and the corresponding avidities of the obtained antisera. The ability of Irgarol 1051 to compete for the antibody binding sites with 11 horseradish peroxidase enzyme tracers, differing in the chemical structures of the hapten, has been investigated. The present paper demonstrates that high-quality antibodies and, therefore, immunoassays reaching very low detection limits could be predicted by molecular modeling studies of the analyte conformations and of the immunizing haptens' geometries, hydrogen-bonding capabilities, and electronic distributions. Two of the ELISAs obtained have been optimized to obtain reproducible immunoassays. The dynamic ranges of both assays are between 30 and 200 ng/L, and the limits of detection are approximately 16 ng/L. The reported immunoassays have been evaluated and validated by analyzing spiked and real seawater samples. Irgarol 1051 has been found to be present in two of the geographical locations analyzed at concentration levels dependent on the time of year. The analytical results obtained with these immunoassays have been validated by chromatographic methods.

Animals↗

PubMed1998

Application of C18 disks followed by gas chromatography techniques to degradation kinetics, stability and monitoring of endosulfan in water.

A comparative degradation study of endosulfan spiked at 35 micrograms/l in water using photocatalysis with (FeCl3/H2O2)/(TiO2/H2O2) and photolysis using either a xenon arc lamp and/or sunlight was performed. After irradiation the water samples were preconcentrated using C18 solid-phase disk extraction and analysis by gas chromatography-electron capture and mass spectrometric detection. Endosulfan sulphate was found in the photodegradation studies. Endosulfan showed high stability in water when it was exposed to sunlight and xenon are lamp, but by means of photocatalysis with FeCl3/H2O2, TiO2/H2O2, the degradation was very fast with half lives varying from 59-98 min. The degradation kinetics followed a first order reaction and the R.S.D. of rate constants, for n = 3, varied from 4-17%. The stability of endosulfan on C18 Empore disks has been determined at 20 degrees C, 4 degrees C and -20 degrees C for periods up to 3 months. Endosulfan was not degraded on C18 Empore disks. Ground water samples from south of Spain (Almeria) were monitored during 1 year. The compounds alpha-, beta- and endosulfan sulphate were detected at concentration values varying from 0.5-540 ng/l.

Chromatography, Gas↗

PubMed1997

Identification of ionic chloroacetanilide-herbicide metabolites in surface water and groundwater by HPLC/MS using negative ion spray.

Solid-phase extraction (SPE) was combined with high-performance liquid chromatography/high-flow pneumatically assisted electrospray mass spectrometry (HPLC/ ESP/MS) for the trace analysis of oxanilic and sulfonic acids of acetochlor, alachlor, and metolachlor. The isolation procedure separated the chloroacetanilide metabolites from the parent herbicides during the elution from C18 cartridges using ethyl acetate for parent compounds, followed by methanol for the anionic metabolites. The metabolites were separated chromatographically using reversed-phase HPLC and analyzed by negative-ion MS using electrospray ionization in selected ion mode. Quantitation limits were 0.01 microgram/L for both the oxanilic and sulfonic acids based on a 100-mL water sample. This combination of methods represents an important advance in environmental analysis of chloroacetanilide-herbicide metabolites in surface water and groundwater for two reasons. First, anionic chloroacetanilide metabolites are a major class of degradation products that are readily leached to groundwater in agricultural areas. Second, anionic metabolites, which are not able to be analyzed by conventional methods such as liquid extraction and gas chromatography/mass spectrometry, are effectively analyzed by SPE and high-flow pneumatically assisted electrospray mass spectrometry. This paper reports the first HPLC/MS identification of these metabolites in surface water and groundwater.

Acetamides↗

PubMed1997

Stability of pesticides stored on polymeric solid-phase extraction cartridges.

The stability of four pesticides (desethylatrazine, fenamiphos, fenitrothion and fonofos) was examined under different storage conditions after preconcentration in disposable solid-phase extraction (SPE) cartridges containing new polymer sorbent materials (Hysphere-1, IST EnviroLut and LiChrolut). Complete recovery for all the compounds was observed in precolumns kept at -20 degrees C for 1 month when preconcentrating 26 ml of ground water sample spiked at 10 micrograms/l. Degradation of fenamiphos and fenitrothion occurred in precolumns stored at 4 degrees C and at room temperature after 1 month. Fonofos was stable when compared to their storage in C18 precolumns. Problems in the quantification of the analytes after storage at 4 degrees C and at room temperature were encountered due to the presence of many interfering peaks in the chromatograms. Analysis of blanks with C18 precolumns was carried out, to determine the interferences. The stability of the pesticides was also examined in acidifed and non-acidified ground water in order to compare it to the stability of pesticides stored on SPE cartridges. Significant losses of fenamiphos and fenitrothion were achieved and were related to the pH of the water sample and their chemical structure. Finally, the new polymeric sorbent Hysphere-I was evaluated in terms of breakthroughs and compared with those of C18, obtaining higher recoveries for desethylatrazine.

Atrazine↗

PubMed1997

Determination of polar priority phenols at parts per trillion levels in water using on-line liquid-solid extraction followed by liquid chromatography with coulimetric detection.

A high-sensitivity method for the determination of polar phenolic compounds in water samples was developed. Water samples were preconcentrated using on-line solid-phase extraction with LiChrolut EN sorbent and afterwards were analyzed by liquid chromatography and dual coulimetric detection. The first electrode was set at low potential (250 mV) for sample clean up whereas the second one was used for analytical purposes. The system could not be used in its reductive form due to the lack of reversibility on the electrochemical behaviour of nitrophenols. Detection limits at part per trillion level were obtained using only 5 ml of water. Additionally, the large cell constant of the coulimetric detector lead to low values of coefficients of variation (+/- 6) when working with river water.

Chromatography, High Pressure Liquid↗

PubMed1996

Determination of parts per trillion levels of organophosphorus pesticides in groundwater by automated on-line liquid-solid extraction followed by liquid chromatography/atmospheric pressure chemical ionization mass spectrometry using positive and negative ion modes of operation.

Liquid chromatography/atmospheric pressure chemical ionization mass spectrometry with positive and negative ion modes of operations was used for the trace determination of several organophosphorus pesticides, (E)- and (Z)-mevinphos, dichlorvos, azinphos-methyl, azinphosethyl, parathion-methyl, parathion-ethyl, malathion, fenitrothion, fenthion, chlorfenvinphos, and diazinon, in groundwater. This method required only 100 mL of water, and it was combined with a prior automated online liquid-solid extraction step using an OSP-2 autosampler containing C18 cartridges. The limit of quantitation (LOQ) varied between 5 and 37 ng/L in positive ion (PI) mode. Under negative ion (NI) mode of operation, only the parathion group (both parathions and fenitrothion) had a better sensitivity as compared to that in PI mode, with a LOQ of 5-15 ng/L, whereas the rest of pesticides had 2-4 times higher LOQs as compared to those in PI mode. Selected ion monitoring of the group-specific fragment of the organophosphorus pesticides, e.g., [(CH3O)2PO2]- or the [M + H]+ ions, under NI or PI mode, respectively, was used. Sample cone voltage varied from 10 to 130 V. This parameter influenced the transmission and fragmentation of quasi-molecular ions, and it was optimized to achieve identification capabilities with the highest sensitivity. At 20 V, good fragmentation was obtained for most of the studied analytes. The system was used for the certification of a groundwater sample spiked at the nanograms per liter level with organophosphorus pesticides provided by Aquachek.

Chromatography, Liquid↗

PubMed1995

Trace determination of herbicides in estuarine waters by liquid chromatography-high-flow pneumatically assisted electrospray mass spectrometry.

High-flow pneumatically assisted electrospray (ESP) was applied to the characterization of triazine (atrazine, simazine, ametryne, cyanazine, deethylatrazine and deisopropylatrazine), phenylurea (chlortoluron++, isoproturon, diuron, linuron and diflubenzuron) and other priority herbicides (alachlor, metolachlor). In LC-ESP-MS the [M+Na]+ ion was used as the base peak in most cases, with the exception of chlorotriazines, which showed [M+H]+ as the base peak. When LC-TSP-MS was used, [M+H]+ was the base peak for many of the pesticides, with the exception of linuron and diflubenzuron, which showed [M+NH4]+ as the base peak. The ESP results were compared with those obtained with thermospray (TSP). LC-TSP-MS offered greater sensitivity for triazines than phenylurea herbicides, whereas the use of LC-ESP-MS offered an enhancement in sensitivity for phenylurea herbicides. As regards the fragmentation obtained using both techniques, ESP offered a considerable amount of structural information for the different chlorotriazines studied when the extraction voltage was increased from 20 to 40 V. Liquid-liquid extraction with dichloromethane was used for the trace enrichment of the different herbicides in estaurine water samples from the Elorn river (France). The presence of the different triazine metabolites, atrazine, simazine, metolachlor, isoproturon and diuron was confirmed by both LC-MS techniques.

Chromatography, High Pressure Liquid↗

PubMed1995

Determination of organophosphorus pesticides and their transformation products in river waters by automated on-line solid-phase extraction followed by thermospray liquid chromatography-mass spectrometry.

The trace-level determination of ten priority organophosphorus (OP) pesticides (e.g., chlorpyrifos-methyl, diazinon, disulfoton, fenthion, fenamiphos) and various transformation products (TPs; e.g., disulfoton sulfoxide, fenthion sulfoxide etc.) using automated on-line solid-phase extraction (SPE) with C18 precolumns followed by LC-MS and thermospray interface with time-scheduled selected-ion monitoring (SIM) was developed. Two main ions (usually [M+H]+ and [M+NH4]+ or [M+CH3CN]+) were used for each pesticide in the positive ion (PI) detection mode, while [M-H]- and [M+HCOO]- ions were used in the negative ion (NI) mode. The proposed method requires 100 ml of sample for a limit of detection (LOD) of 0.01-0.1 microgram/l. Calibration graphs were constructed by preconcentrating 100 ml of water spiked with the pesticide mixture at various concentrations (from 0.025 to 2 microgram/l). Good linearity was observed for most of the analytes studied. The experimental setup described in this paper was applied to study the kinetics of degradation of ten organophosphorus pesticides in spiked river water samples. The different samples were first analyzed by an automated on-line precolumn exchange system (OSP-2) followed by LC with diode array detection. To confirm the identity of the organophosphorus pesticides detected, the samples were then analyzed by automated on-line SPE-LC-MS. The method permitted unequivocal identification of many of the TPs formed during the experiments, e.g., the oxo-derivatives of chlorpyrifos-methyl, temephos and pyridafenthion, fenamiphos sulfoxide. Many of these TPs are here reported for the first time since previously used MS-based techniques were not sensitive enough.

Biodegradation, Environmental↗

PubMed1995

Dioxins, furans and AHH-active PCB congeners in eggs of two gull species from the western Mediterranean.

Polychlorinated biphenyls, dibenzodioxins and dibenzofurans were analysed in eggs of a protected gull species, the Audouin's Gull (Larus audouinii) and compared to those of the Yellow-legged Gull (Larus cachinnans), both breeding in the Western Mediterranean (Ebro Delta and Medes Islands, respectively). Differences in concentrations as well as in congener profiles reflected differences in both habitat and diet of the two species. Levels of AHH-active PCB congeners were lower in Yellow-legged Gull (0.4-1.6 micrograms/g d.w) than in Audouin's Gull eggs (1.2-33.9 micrograms/g d.w.). These concentrations, expressed in international toxic equivalence factors (i-TEQ/g d.w.), were on average 24 times higher in the Audouin's gull. I-TEQ levels due to dioxins were also higher in this species by a factor of ca. 7. I-TEQ levels related to PCBs resulted 90-230 times higher than those of dioxins and furans. Thus, AHH-inducing PCBs might represent even higher toxicological hazards than dioxins and furans to some populations of seabirds. The necessity of assessing the impact of these compounds in rare and protected species is pointed out.

Animals↗