Biomedical subjects

F Borrull

Publications and source records attributed to F Borrull.

35 records · Page 2Linked to original sources

PubMed2000

Determination of phthalate esters in water samples by solid-phase microextraction and gas chromatography with mass spectrometric detection.

Solid-phase microextraction (SPME) with an 85 microm polyacrylate fiber, coupled to gas chromatography-mass spectrometry was used to determine six phthalate esters and bis(2-ethylhexyl) adipate in water samples. The variables affecting the SPME absorption process were optimized and the method developed was applied to analyze both tap and commercial mineral water samples as well as water from the Ebro river and fishing and industrial ports. For real samples, the linear range in full scan acquisition mode was between 0.02 and 10 microg l(-1) for most compounds, and the limits of detection of the method were between 0.006 and 0.17 microg l(-1). Commercial water samples contained in recipients which were made from different materials were analyzed, and the influence of the material of the recipients on the concentration of phthalates was evaluated.

Esters↗

PubMed2000

Comparative study of capillary zone electrophoresis and micellar electrokinetic capillary chromatography for the separation of naphthalenedisulfonate isomers.

We investigated the separation of a test mixture of nine substituted and unsubstituted naphthalenedisulfonate isomers by capillary electrophoresis with a UV diode array detector. In particular, we focused on how the composition of the running buffer affected the separation selectivity. When capillary zone electrophoresis was carried out, the best results were obtained when organic solvents such as ethanol or propan-2-ol were added. Eight peaks were baseline separated but in no case were all the unsubstituted isomers separated. Therefore, capillary electrophoretic separation of the compounds was examined in the presence of micellar agents, such as sodium dodecyl sulfate, polyethylene glycol dodecyl ether (Brij 35) and cetyltrimethylammonium bromide. All the substituted isomers and two of the unsubstituted isomers were well resolved within 20 min by micellar electrokinetic capillary chromatography when Brij 35 was used as micellar agent. Separations were reproducible, in terms of peak area and migration time, under these conditions.

Chromatography, Micellar Electrokinetic Capillary↗

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

Determination of amoxicillin in plasma samples by capillary electrophoresis.

We have developed a capillary zone electrophoresis (CZE) method for determining amoxicillin in animal plasma samples. Sample clean-up involved solid-phase extraction onto Sep-Pak C18 cartridges followed by elution with water-methanol (85:15). This paper describes two different techniques to increase the sensitivity of the CZE method: field-amplified sample injection (FASI) and electrokinetic injection. We have enhanced the detection limit to 280 micrograms l-1 by the FASI technique.

Amoxicillin↗

PubMed1999

Optimization of solid-phase microextraction conditions using a response surface methodology to determine organochlorine pesticides in water by gas chromatography and electron-capture detection.

A response surface methodology was applied to optimise the solid-phase microextraction (SPME) conditions using a polyacrylate-coated fiber to determine thirteen organochlorine pesticides from water. Analyses were performed using gas chromatography-electron-capture detection. Variables affecting absorption in both the headspace and immersion extraction were optimised by using a response surface generated with a Doehlert design, and the results were compared. The immersion SPME method was selected since higher recoveries were obtained for most of the compounds studied. The method developed was applied to the analysis of tap and Ebro river water samples. The linear range of most pesticides for real samples was found to be between 0.001 and 2.5 micrograms l-1 and the limits of detection were between 0.15 and 0.35 ng l-1. The repeatability and the reproducibility between days of the method (n = 6), expressed as relative standard deviation, for tap water spiked at a level of 1 ng l-1 were between 5.7 and 25.6% and between 7.6 and 26.5%, respectively.

Chromatography, Gas↗

PubMed1999

Solid-phase microextraction of the antifouling Irgarol 1051 and the fungicides dichlofluanid and 4-chloro-3-methylphenol in water samples.

Three pesticides usually added to paint formulations, Irgarol 1051, dichlofluanid and 4-chloro-3-methylphenol, were determined by solid-phase microextraction (SPME) with 85-micron polyacrylate fibers and gas chromatography-mass spectrometry. The parameters affecting the SPME process (the pH, the addition of salt to the sample, and the time and temperature of the absorption step) were optimized. The method developed was applied to the analysis of water samples from Ebro river, marinas and fishing ports. The method enables these compounds to be detected at concentrations between 0.2 and 3.0 micrograms l-1 under full scan conditions and between 0.05 and 0.08 microgram l-1 under SIM mode.

Absorption↗

PubMed1999

Evaluation of different electrolyte systems and on-line preconcentrations for the analysis of haloacetic acids by capillary zone electrophoresis.

This study compares the sodium chromate, potassium hydrogenphthalate, 2,6-naphthalenedicarboxylic acid dipotassium and sodium tetraborate electrolyte systems, for determining haloacetic acids using capillary zone electrophoresis with and without modified electroosmotic flow. In order to detect low concentrations of these compounds, an on-line preconcentration step was carried out. Results were good when standard solutions were analysed, but when the method was applied to real samples, the sample had to be pretreated to decrease the interference of the matrix. For this reason, a solid-phase extraction process with LiChrolut EN cartridges was applied to clean up the sample before the injection.

Acetates↗

PubMed1998

Comparative study of a solid-phase extraction system coupled to capillary electrophoresis in the determination of haloacetic compounds in tap water.

This study compares four different commercial sorbents, LC-SAX (a quaternary ammonium anion exchanger), LiChrolut EN (a highly crosslinked styrene-divinylbenzene), Envi-Carb (a graphitized carbon black) and Oasis HLB [a macroporous poly(divinylbenzene-co-N-vinylpyrrolidone) copolymer], for the solid-phase extraction (SPE) of various haloacetic compounds from aqueous samples. The recoveries with the different sorbents were studied by coupling an off-line SPE system to capillary electrophoresis with indirect photometric detection. The recoveries were highest when LiChrolut EN was used. The limits of detection for the compounds are in the low microgram per litre range and the recovery values are over 80% for dichloroacetic acid and trichloroacetic acid, two of the most habitual haloacetic acids in chlorinated water, when 500 ml of standard solution was preconcentrated using this sorbent. Finally, the performance of the method with different water samples, the effect of chlorination in a treatment plant and the evolution of the haloacetic acids in the water distribution system were tested and the results were compared with those obtained using liquid-liquid extraction and gas chromatography-mass spectrometry.

Dichloroacetic Acid↗

PubMed1998

On-line coupling of solid-phase extraction to gas chromatography with mass spectrometric detection to determine pesticides in water.

A group of pesticides with different chemical structures was determined in water by on-line coupling of solid-phase extraction to gas chromatography with mass spectrometric detection through an on-column interface. A 10 mm x 2 mm I.D. precolumn packed with PLRP-S was selected for the solid-phase extraction process. The parameters affecting the transfer of the analytes from the precolumn to the GC system (e.g. flow-rate, temperature and solvent vapor exit time) were optimized. An organic modifier was added to the sample before the extraction process to avoid adsorption problems. The use of the MS detector under selected ion monitoring acquisition enabled the analytes to be quantified at sub microgram-per-litre levels preconcentrating only 10 ml of sample, and the limits of detection (S/N = 3) were between 2 and 20 ng l-1. The method was applied to the determination of the pesticides in tap and river water, and molinate was determined in Ebro river water.

Gas Chromatography-Mass Spectrometry↗

PubMed1998

Capillary zone electrophoresis with indirect UV detection of haloacetic acids in water.

A capillary zone electrophoresis (CZE) system for determining haloacetic acids in water was optimized with indirect photometric detection. Two different carrier electrolytes, potassium hydrogenphthalate and sodium 2,6-naphthalenedicarboxylate, were evaluated in terms of sensitivity and two different electroosmotic flow modifiers, tetradecyltrimethylammonium bromide and hexadecyltrimethylammonium bromide, were tested. Parameters such as electrolyte concentration and pH, and the concentration of the electroosmotic flow modifiers, which affect the CZE separations, were investigated. The method was used to determine haloacetic acids in chlorine tap water using the liquid-liquid extraction process.

Acetates↗

PubMed1998

Identification of pesticides by liquid chromatography--particle beam mass spectrometry using electron ionization and chemical ionization.

Liquid chromatography-mass spectrometry (LC-MS) with a particle beam (PB) interface is used to separate and identify a group of pesticides. The mass spectra obtained under the different ionization modes, electron ionization (EI) and positive and negative chemical ionization (PCI and NCI) are compared. The operating conditions under each mode, determined by studying the influence on the ion abundance of the ion source temperature of the EI mode, and the gas pressure and ion source temperature in the methane CI were optimized. EI was more sensitive than PCI and NCI and of the latter two modes, NCI gave higher responses, especially for organophosphorus compounds. When on-line solid-phase extraction-LC-PB-MS was applied to real samples, limits of detection in full scan mode were in the range of 0.5 and 10 micrograms l-1 for EI. The analysis of real samples by on-line solid-phase extraction-LC-PB-MS enabled EI detection of one of the pesticides studied and confirmation by PCI and NCI. The combined EI/CI information also enabled the detection of some non-target compounds.

Chromatography, Liquid↗

PubMed1998

New chemically modified polymeric resin for solid-phase extraction of pesticides and phenolic compounds from water.

A new chemically modified polymeric resin, with an o-carboxybenzoyl moiety, is developed to be used in the on-line solid-phase extraction (SPE) of some pesticides and phenolic compounds from aqueous samples, in order to obtain better breakthrough volumes than other commercial sorbents. The chemical introduction of this moiety improves the efficiency of SPE by providing better surface contact with aqueous samples. This synthesized sorbent enables higher volumes of sample to be concentrated for determining polar compounds. When analyzing real samples, tap and river waters, different quantities of sulphite were added to decrease the initial band due to fulvic and humic acids. The matrix peaks decreased and there were no losses in the studied compounds observed when 500 and 1000 microliters of 10% Na2SO3 solution for every 100 ml of sample were added to tap and river water, respectively.

Fresh Water↗

PubMed1997

Determination of polycyclic aromatic hydrocarbons in waters by use of supercritical fluid chromatography coupled on-line to solid-phase extraction with disks.

The potential of supercritical fluid chromatography (SFC) coupled on-line to solid-phase extraction (SPE) with disks for determining sixteen different polycyclic aromatic hydrocarbons (PAHs) was assessed. A preliminary study of the chromatographic separation was conducted that led to the use of SPE coupled to SFC for improved detection limits. Disks of two different materials, i.e., C18 and polystyrene-divinylbenzene, were assayed in terms of the variables influencing the extraction step. C18 disks provided the best results, with detection limits ranging from 0.1 to 1.5 micrograms l-1. The ensuing method was applied to river and tap water with good repeatability and reproducibility, and no interference from the sample matrix.

Chromatography, Liquid↗

PubMed1997

Solid-phase extraction of phenols and pesticides in water with a modified polymeric resin.

A comparative study of a chemically modified polymeric resin which has a benzoyl group and several commercial sorbents, such as PLRP-S, Envi-chrom P and LIChrolut EN, for the solid-phase extraction of various phenolic compounds and pesticides was carried out. Selectivity and breakthrough volumes for these compounds with different sorbents were studied by coupling an on-line solid-phase extraction system with a modified liquid chromatograph equipped with a UV detector. After determining the chromatographic conditions, linearity range and detection limits, the method was applied to the determination of these compounds in drinking and surface water. For 25 ml of sample, the recovery was > 70% for all the compounds, except for 4-nitrophenol (62%), and detection limits were between 0.2 and 0.8 microgram I-1.

Chromatography, Liquid↗

PubMed1996

On-line solid-phase extraction coupled to supercritical fluid chromatography to determine phenol and nitrophenols in water.

Determining of phenol and nitrophenols using solid-phase extraction on-line coupled to supercritical fluid chromatography (SFC) is studied. SFC quickly separated the compounds studied, in less than 6 min, and solid-phase extraction was used to decrease the limits of detection. C18, PLRP-S and a highly cross-linked styrene-divinylbenzene copolymer in a 10 x 3 mm I.D. laboratory-packed precolumn were tested comparatively as sorbents in the preconcentration step. Tetrabutylammonium bromide was used as ion-pair reagent in the extraction process to increase breakthrough volumes, mainly for phenol. Performance of the method was checked with tap and river waters.

Chromatography, High Pressure Liquid↗

PubMed1993

Determination of phenols at the ng/1 level in drinking and river waters by liquid chromatography with UV and electrochemical detection.

Solid-liquid extraction of samples and liquid chromatography with UV and electrochemical detection with laboratory-made microcolumns were applied to the separation and identification of phenols and substituted phenols in waters. The compounds mainly studied were the eleven phenols considered as priority pollutants by the US Environmental Protection Agency. Chromatographic separation was carried out with several water-methanol isocratic mobile phases; use of the autoincrement mode of the electrochemical detector allowed the compounds in the samples to be confirmed. The chromatographic system worked automatically. The detection limits obtained with prior concentration of the samples were 40-600 ng/l, depending of the phenol. Electrochemical detection was used for the determination of phenols in river and drinking waters; phenols at the ng/l level was detected.

Chromatography, Liquid↗

PubMed1992

Determination of carboxylic acids, sugars, glycerol and ethanol in wine and grape must by ion-exchange high-performance liquid chromatography with refractive index detection.

Method to determine the major carboxylic acids, sugars, glycerol and ethanol in wine and grape must was developed using an ion-exchange column and refractive index detector. A solid-phase extraction method with a strong anion exchanger was used to determine these compounds in sweet wines and in grape musts. With this method it is possible to determine malic acid in sweet wines and in grape musts without interference from sugars. This high-performance liquid chromatographic method was compared with standard methods of analysis. There was good agreement in the accuracy and precision of the compared methods.

Carbohydrates↗