Biomedical subjects

R Batlle

Publications and source records attributed to R Batlle.

10 recordsLinked to original sources

PubMed2006

On-line strategies for determining trace levels of nitroaromatic explosives and related compounds in water.

We report the development and tests of several systems for the simultaneous determination of 18 energetic compounds and related congeners in untreated water samples. In these systems a Restricted Access Material trap or liquid-chromatography precolumn (with a C(18) or porous graphitic carbon, PGC, stationary phase) followed by a PGC analytical column are used for sample clean-up, enrichment and separation of the trace level analytes, which are then analyzed by mass spectrometry (MS). The relative merits of two MS ionization interfaces (atmospheric pressure chemical ionization, APCI, and atmospheric pressure photoionization, APPI) were also compared for the MS identification and quantification of these analytes. APCI was found to be superior in cases where both alternatives are applicable. A major drawback when applying APPI is that no signal is obtained for the cyclic nitramines and nitrate esters. Using APCI, a wide spectrum of unstable compounds can be determined in a single analysis, and the feasibility of using large volume samples (up to 100 mL) in combination with the sensitivity of the MS detection system provide method detection limits ranging from 2.5 pg/mL (for 2,4-dinitrotoluene and 2,6-diamino-6-nitrotoluene) to 563 pg/mL (for pentaerythritol tetranitrate, PETN), with repeatability ranging from 2 to 7%. Other chemometric parameters such as robustness, selectivity, repeatability, and intermediate precision were also evaluated in the validation of the extraction methods for use in water analysis. Tests with untreated groundwater and drinking water samples, spiked with 20 ng of the analytes, yielded results similar to those obtained with high purity water samples.

Analytic Sample Preparation Methods↗

PubMed2005

Solid- and vapor-phase antimicrobial activities of six essential oils: susceptibility of selected foodborne bacterial and fungal strains.

The antimicrobial activity of essential oils (EOs) of cinnamon (Cinnamon zeylanicum), clove (Syzygium aromaticum), basil (Ocimum basillicum), rosemary (Rosmarinus officinalis), dill (Anethum graveolens), and ginger (Zingiber officinalis) was evaluated over a range of concentrations in two types of contact tests (solid and vapor diffusion). The EOs were tested against an array of four Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, Enterococcus faecalis, and Listeria monocytogenes), four Gram-negative bacteria (Escherichia coli, Yersinia enterocolitica, Salmonella choleraesuis, and Pseudomonas aeruginosa), and three fungi (a yeast, Candida albicans, and two molds, Penicillium islandicum and Aspergillus flavus). The rationale for this work was to test the possibility of creating a protective atmosphere by using natural compounds that could extend the shelf life of packaged foodstuffs while minimizing organoleptic alterations. In the solid diffusion tests, cinnamon and clove gave the strongest (and very similar) inhibition, followed by basil and rosemary, with dill and ginger giving the weakest inhibition. The fungi were the most sensitive microorganisms, followed by the Gram-positive bacterial strains. The Gram-negative strain P. aeruginosa was the least inhibited. The composition of the atmosphere generated by the EOs, and their minimum inhibitory concentrations (MICs), were determined using a disk volatilization method, in which no inhibition from rosemary or basil was observed. Cinnamon and clove, once again, gave similar results for every microorganism. As a general rule, MIC (fungi) << MIC (bacteria) with no clear differences between Gram-positive or -negative strains except for P. aeruginosa, which was not inhibited by any of the EOs in the vapor phase. The atmosphere generated from the EOs was analyzed by means of solid-phase microextraction combined with gas chromatography-ion trap mass spectrometry. Differences among the volatiles in the EOs, which may be responsible for the differences in their antimicrobial performances, were found.

Anethum graveolens↗

PubMed2005

Supercritical fluid extraction of energetic nitroaromatic compounds and their degradation products in soil samples.

This paper explores the use of supercritical fluid extraction (SFE), in combination with various analyte collection strategies, for extracting energetic nitroaromatic compounds and their degradation products from soil samples. The required selectivity has been achieved by a combination of an SFE program and active trapping. Several different collection strategies were tested, using a selection of liquids (methanol, toluene, methyl tert-butyl ether, acetonitrile), inert and solid-phase extraction materials (Nexus, Oasis, LiChrolut), and 1-cm liquid chromatography precolumns (porous graphitic carbon, PGC). The best results were obtained using SFE in combination with a PGC precolumn. This setup allows on-line cleanup of the extract, and comparable results were obtained using either GC-ECD or GC-chemical ionization-MS for confirmatory analysis. The time required for a complete analysis was less than 60 min, and only 1 mL of toluene was needed for a 0.5-g representative sample. In contrast, the EPA standard method 8330 required 18-h sonication and 20 mL of acetonitrile for a 4.0-g sample and further time for sample cleanup and HPLC analysis. The method presented here provides method detection limits in the low-nanogram range, with relative standard deviations lower than 7%. The optimized method has been compared and validated with EPA method 8330 in terms of efficiency parameters such as robustness, accuracy (trueness and precision), and capability of detection. The validation demonstrated that the two analytical methodologies give comparable performance for the determination of nitroaromatic compounds, but SFE is superior for analyzing amine degradation products.

Journal Article↗

PubMed2003

Determination of nitroaromatic compounds in air samples at femtogram level using C18 membrane sampling and on-line extraction with LC-MS.

This paper explores the use of C18 solid-phase extraction membranes for sampling very low concentrations of nitroaromatic compounds in the atmosphere. After sampling, analytes trapped in the membrane are desorbed on-line directly by a chromatographic mobile phase. The analytes are then separated onto a porous graphitic carbon (PGC) HPLC column. Finally, they are analyzed by an LC-MS/MS detector equipped with an atmospheric pressure chemical ionization (APCI) interface. The method was validated by controlled exposure of the membranes to standard gaseous mixtures of 2,4,6-trinitrotoluene (TNT) and 2,4-dinitrotoluene (2,4-DNT). The developed method was fully characterized, and no breakthrough was observed when sampling volumes up to 9.2 m3. Analyses of membranes following medium- and long-term storage demonstrated that samples could be stored on the C18 membranes without degradation or losses. In addition, the results obtained with this technique were compared with those obtained by a gas chromatographic method in which analytes were collected on Tenax TA and thermally desorbed. The developed method allows sampling at flow rates of 15 L/min and has method detection limits in the femtogram/liter range, with a relative standard deviation lower than 10%. An additional advantage of this method is that it separates most of the TNT and DNT isomers, as demonstrated by applying the method to the analysis of headspace over military-grade TNT explosives.

Journal Article↗

PubMed2001

Determination of gaseous toluene diisocyanate by use of solid-phase microextraction with on-fibre derivatisation.

An SPME method was developed for sampling gaseous 2,4-toluene diisocyanate (2,4-TDI) involving derivatisation of the isocyanate by reacting with dibutylamine (DBA). The TDI-DBA derivative thus formed was determined by LC-MS-MS utilising atmospheric pressure chemical ionisation (APCI). As a first step, DBA was loaded onto a poly(dimethylsiloxane)/divinylbenzene (PDMS-DVB) fibre coating by direct vapour-phase extraction of a highly concentrated diethyl ether solution of DBA. The DBA-loaded fibre was then exposed to an artificially generated atmosphere of gaseous 2,4-TDI. The linearity of the method ranged from 52.8 to 3100 microg m(-3) (6.8 to 400 ppbv) with a sampling time of 60 min. The proposed method has been applied to 2,4-TDI determination in an artificially generated dynamic standard atmosphere, yielding an approximate method detection limit (MDL) of 2 microg m(-3) (0.25 ppbv). This concentration is one twentieth of the Occupational Safety and Health Administration (OSHA) 8-hour time-weighted average (TWA) exposure limit. The sampler with the PDMS-DVB-DBA coating was found to be stable and retains the required amount of DBA for at least 10 days, an important feature for sampling systems with potential in-situ applications.

Journal Article↗

PubMed2001

Development of a personal isocyanate sampler based on DBA derivatization on solid-phase microextraction fibers.

The design and evaluation of a portable diffusive sampler for isocyanates is described. The sampler employs dibutylamine (DBA) loaded onto 60-microm polydimethylsiloxane-divinylbenzene (PDMS-DVB) solid-phase microextraction (SPME) fibers. The DBA-isocyanate derivative is then desorbed by sonication and analyzed by LC-MS using atmospheric pressure chemical ionization (APCI). The samplers are calibrated (i.e. the uptake rate is calculated) by exposing them to a known concentration of hexamethylene diisocyanate (HDI) in a standard gas-generation chamber. The uptake rate for the proposed method, at room temperature (25 degrees C), is 1.13 pg (min ppb(v))(-1) and the method detection limit is 3.2 microg m(-3), equivalent to less than 10% of the airborne time-weighted average (TWA) exposure limits recommended by both the National Institute for Occupational Safety and Health (NIOSH) and the American Conference of Governmental Industrial Hygienists (ACGIH). Practical points that should be considered when using the SPME device as a diffusive sampler are discussed.

Air Pollutants, Occupational↗

PubMed1999

Use of solid-phase microextraction for the analysis of bisphenol A and bisphenol A diglycidyl ether in food simulants.

A new method has been developed to simultaneously analyse bisphenol A (BPA) and bisphenol A diglycidyl ether (BADGE) in aqueous based food simulants. The method consists on direct immersion solid-phase microextraction (SPME) of the analytes from the liquid matrix and subsequent chromatographic analysis by gas chromatography-mass spectrometry. Using the proposed method, a whole analysis (including chromatographic step) can be completed in less than 40 min, with minimum sample handling. The SPME method shows good analytical performance for simultaneous BPA and BADGE analysis, except for BADGE determination in the aqueous alcohol (simulant C) solution. Detection limits ranging from 0.1 to 2.0 ng/g for BPA and from 13 to 15 ng/g from BADGE were obtained, with a linear range from the low-ng/g to several-microg/g range for BPA and from 0.1 microg/g to 40 microg/g for BADGE. A possible optimisation method has been also developed and introduced.

Benzhydryl Compounds↗

PubMed1999

Assessing the suitability of recycled plastics used as agricultural soil covers: migration study and experimental harvest.

The present work is focused on evaluating the suitability of recycling postconsumer agricultural plastic films again for the same use. The criteria to assess the suitability was based on migration study. Both overall and specific migration tests were performed, and the results obtained (ranging from 0.14 to 1.27 mg/dm(2) for overall migration and from not detectable to 6.98 microg/dm(2) for specific migration) show how, from this point of view, the recycled material can be safely proposed to be used again as agricultural soil covers. A theoretical discussion about the migration process is also presented and a simple mathematical model was applied to the data obtained, showing how total migration which is experimentally detected is theoretically predictable. These conclusions found were used to design and develop a controlled crop of tomato by using this recycled film. The use of the recycled plastic in the whole process and the behavior and properties of the pesticides absorbed in the postconsumer film are discussed.

Agriculture↗

PubMed1998

Design of a test for migration studies in the vapour phase.

A new test for migration studies in the vapour phase has been developed. The system consists of placing the packaging material containing the potential migrants in a glass vial together with the solid adsorbent, Tenax GC. The vial is introduced into an oven at a controlled temperature for different periods of time. Once the migration test has finished, Tenax is extracted by supercritical fluid chromatography (SFE) and analysed by GC-ECD. Migration conditions of 7 days at 80 degrees C are proposed. The results obtained are discussed.

Adsorption↗

PubMedDate not supplied

Determination of plastic monomers in water by solid-phase microextraction coupled with liquid chromatography.

A method is presented for the determination of 2 major plastic monomers, terephthalic acid and vinyl acetate, which are widely used to manufacture plastics that come in contact with foods. The analytes are extracted from aqueous solution by using solid-phase microextraction, followed by quantitation by liquid chromatography (LC) with UV detection. Multivariate optimization was applied and is described. The optimized method has linear ranges of 5-150 microg/g for terephthalic acid and 7.5-100 microg/g for vinyl acetate. Coefficients of variation at a spiking level of 20 microg/g were 13.6% for terephthalic acid and 3.1% for vinyl acetate; detection and quantitation limits were 0.59 and 1,99 microg/g, respectively, for terephthalic acid and 1.56 and 5.20 microg/g, respectively, for vinyl acetate. The characteristics of both the extraction technique and its coupling with LC are described and discussed.

Chromatography, Liquid↗