Raquel T Gettar

National Scientific and Technical Research Council, Buenos Aires, Buenos Aires F.D., Argentina

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Publications (20)38.31 Total impact

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    ABSTRACT: This study presents the analysis of two series of concentrations of airborne particulate matter (APM) collected in two exploratory campaigns aimed at elucidating the source–receptor problem (SRP) in the metropolitan area of Buenos Aires. Although several techniques have been previously applied to interpret these measurements, we have almost exclusively used here the method of angular distances among objects (ADO) to discuss its advantages as a tool in understanding environmental questions within the source–receptor framework. We present a simple method of calculating the ADO, explain its chemical interpretation and the information that is possible to get by classifying the angular distances. A comparison among ADO with principal component analysis and Kohonen artificial neural networks is also discussed.
    Water Air and Soil Pollution 01/2008; 188(1):235-245. · 1.75 Impact Factor
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    ABSTRACT: El objetivo de este trabajo es el estudio detallado de las características de los aerosoles atmosféricos (TSP, PM2.5-10 y PM2.5) mediante la aplicación de un conjunto de distintas técnicas analíticas complementarias PIXE, Cromatografía Iónica, Difracción de R-X y MEB/EDAX. El estudio de la composición química, iónica, elemental y morfológico a través de diversas técnicas analíticas permitió inferir las fuentes más probables de aerosoles que confluyen en el sitio de recolección. La identificación de las posibles fuentes se complementó mediante un estudio de retro-trayectorias aplicando un modelo de transporte y dispersión atmosférica. The aim of this study is the detailed analysis of atmospheric aerosol characteristics (TSP, PM2.5-10 and PM2.5) applying a variety of different and complementary analytical techniques: PIXE, Ion Cromatography, X-Ray Diffraction and MEB/EDAX. The chemical, ion, elemental and morphologic composition study allowed to identify the most probable sources of the collected aerosols. To further advance in the identification of the possible origin of the sampled aerosols, backward trajectories were obtained with the application of a transport and dispersion model.
    AIP Conference Proceedings 11/2007; 884(2007):74.
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    ABSTRACT: Normal-phase separation of technical grade nonylphenol (t-NP, about 90% 4-nonylphenol), 4-nonylphenol mono-ethoxylate (4-NP1EO) and 4-nonylphenol di-ethoxylate (4-NP2EO) was assessed, with the inclusion of column temperature as an active variable. The compound 2,4,6-trimethylphenol was evaluated for use as internal standard. Isocratic elution with 2-propanol/hexanes mixtures from an amino-silica column and spectrometric UV detection at 277 nm were employed. Technical nonylphenol presented a significant contribution from unknown substances that eluted with retention times similar to that of 4-NP1EO. GC-MS analysis of the unknowns allowed to identify them as isomers of 2-NP. The response of the system to joint variations in flow rate, eluent composition and column temperature was investigated by means of Doehlert statistical experimental design. A model for retention of the analytes as a function of the experimental variables was proposed, and separation selectivity was studied. Selection of the optimal working zone was made through desirability function (D) calculations. Potential co-elution of 2-NP isomers with 4-NP1EO was considered when optimizing the separation. The occurrence of a restricted region of the experimental space where baseline resolution of analytes, associated impurities and internal standard results feasible (D not equal to 0) is apparent.
    Journal of Chromatography A 08/2007; 1157(1-2):227-36. · 4.61 Impact Factor
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    ABSTRACT: A dual-detection technique, consisting of a combination of reversed-phase high-performance liquid chromatography and on-line detection of elemental boron in the column effluents by inductively coupled plasma optical emission spectrometry, was tested for drug analysis. The method was applied to assessing the chemical purity of p-boronophenylalanine (BPA), isotopically enriched in 10B. This compound is employed as a fructose complex solution for biodistribution studies in laboratory and clinical trials of boron neutron capture therapy. Besides the determination of the content of BPA, required for chemical quality controls of solutions of the complex used for infusions, resolution of mixtures of BPA and two usually accompanying residual impurities (phenylalanine and tyrosine) was achieved with UV detection. The limits of detection (in solution) were 1.5 and 0.6 ng ml-1, respectively. In addition, by monitoring a sensitive-element emission wavelength it was possible to jointly observe the elution of boron-containing compounds that may be transparent to UV radiation or to confirm the presence of boron in potential impurities accompanying the drug. Those impurities may arise from the BPA synthesis or may be produced by degradation during the aging of the solutions. Chromatographic peaks corresponding to the amino acids and also to a related inorganic compound were detected in BPA-fructose complex solutions that were stored for different times and under different conditions. An increase in the areas of the peaks attributed to tyrosine and phenylalanine was observed for BPA-fructose solutions stored refrigerated for 1 month to 1 year, suggesting that degradation processes able to reduce the amount of bioavailable BPA could be active.
    Analytical and Bioanalytical Chemistry 06/2007; 388(2):499-503. · 3.66 Impact Factor
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    ABSTRACT: Degradation of citric acid (Cit) at relatively high concentrations by photocatalysis over TiO2 under air bubbling and near UV-light was tested under different conditions. The reaction was improved by addition of H2O2, Fe(III) or both. Minor amounts of H2O2 were effective to enhance the oxidation and the mineralization. H2O2 addition impacts more on the initial rate, while the effect of Fe(III) is more important after prolonged irradiation. The kinetic profiles were analyzed and compared, and the best ratio of reagents was found (1:1:1 H2O2/Cit/Fe molar ratio). However, a lower amount of Fe (1:1:0.2 H2O2/Cit/Fe ratio) was also effective. Similar experiments under the optimal conditions in the absence of TiO2 were performed for comparison. When both H2O2 and Fe(III) were present, the behavior with and without TiO2 was very similar. So far, 3-oxoglutaric acid was detected as a reaction intermediate. A mechanistic analysis is initiated to explain some features of these complex systems.
    Applied Catalysis B: Environmental. 02/2007; 71(s 3–4):117–124.
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    ABSTRACT: Capillary electrophoresis based on non-aqueous solvent background electrolytes was employed, with single and multiple wavelength UV detection, to evaluate discrimination among oligomer components of mixtures of non-ionic, long chain nonylphenol ethoxylates (NPnEO, with n = number of ethoxy units) and their lipophilic degradation products. The tested organic solvents included acetonitrile, methanol, ethanol, 1- and 2-propanol, 1-butanol and tetrahydrofurane in the presence of sodium acetate. A rational variation of composition of background electrolyte solvent mixtures allowed to modify the mobility of electroosmotic flow and the type and degree of interactions between the ionic additive (sodium acetate) and the components of the analyte mixtures. The physicochemical properties of the solvents, such as dielectric constant, viscosity and electron donor-acceptor ability regarding the additive, were considered to improve the resolution of lipophilic compounds with less than three ethoxy groups and the discrimination attainable for longer chain oligomers. The studied methodologies also allowed discerning between surfactants of similar (nominal) ethoxy chain lengths. This was demonstrated by the different peak distribution patterns observed for NPnEO compounds with n = 7.5 and 10, respectively.
    Journal of Chromatography A 06/2006; 1116(1-2):277-85. · 4.61 Impact Factor
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    ABSTRACT: Different nebulizer/expansion chamber combinations were evaluated to assess their performance for sample introduction in the direct coupling with an axial view inductively coupled plasma multielement spectrometer for on-line determination of As and Se species previously separated by ion exchange–high performance liquid chromatography. The column effluents were injected into the plasma without prior derivatization. The instrument operation software was adapted for data acquisition and processing to allow multi-wavelength recording of the transient chromatographic peaks. After optimization of the chromatographic operating conditions, separation of mixtures of inorganic As and Se species, and of inorganic and two organic As species (monomethylarsonic and dimethylarsinic acids), was achieved with excellent resolution. Species discrimination from mixtures of As and Se oxyanions was further improved by the simultaneous element detection at specific analytical wavelengths. Three nebulizers and three spray chambers, employed in seven combinations, were tested as interfaces. Concentric nebulizers associated to a glass cyclonic chamber appear most suitable regarding sensitivity and signal to noise ratio. Measured element detection limits (3 σ) were around 10 ng ml− 1 for all the species considered, making the method a viable alternative to similar procedures that employ volatile hydride generation previous to sample injection into the plasma. Analytical recoveries both for inorganic and organic species ranged between 92 and 107%. The method was demonstrated to be apt for the analysis of surface waters potentially subjected to natural contamination with arsenic.
    Spectrochimica Acta Part B Atomic Spectroscopy 06/2005; · 3.14 Impact Factor
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    ABSTRACT: TiO2-heterogeneous photocatalysis of nitrilotriacetic acid (NTA) at pH 2.5 was studied to establish the kinetic regime and the reaction mechanism. Pure Degussa P-25 and Hombikat UV100 commercial samples were compared. A Langmuirian behavior was observed over P-25. Platinization of the Hombikat sample (0.5 wt.%) caused an important increase on the photocatalytic rate with a change in the kinetics from zero order in the pure precursors to first order in the platinized sample. The nature of the intermediates and their evolution with time were compared on all systems. Glycine, iminodiacetic and oxamic acids have been identified in different proportions, together with ammonium and glycolic acid, depending on the catalyst used. The rapid depletion of NTA was not accompanied by a corresponding total organic carbon (TOC) reduction, but 84% of TOC decrease was obtained on P25 after 24 h, a very reasonable result for refractory compounds. A detailed mechanism is proposed for the photocatalytic reaction, suggested to be the same over the three catalysts here tested.
    Journal of Applied Electrochemistry 01/2005; 35(7):733-740. · 1.84 Impact Factor
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    ABSTRACT: Buenos Aires Metropoli*tan Area (BAMA), composed by Buenos Aires city (34º 38’S, 58º 28’W) and 24 neighbouring districts, constitutes a huge urban conglomerate, with about 14 millioninhabitants and a surface of 4000 km2. It is the third megacity in Latin America and the 10th in the world. Airpollution in Buenos Aires is mainly due to traffic emissions, with an additional contribution from thestationary thermal power plants, located on the Río de la Plata shore. Several studies have shown that the airquality in BAMA is an issue of concern. However, the area still lacks an air-quality monitoring network. Asthe nature of air pollution problems is the result of several sources and transport, dispersion andtransformation mechanisms, there is an increasing interest to understand the complex and multiple factorsthat contribute to the air quality in a place. In some situations, and to some degree, there can be contributionsfrom natural local or remote sources. In order to advance in the characterization and understanding of therelative importance of the different air pollution sources along with the transport and dispersion mechanisms,aerosol samples were collected during 2003 and 2004 at a site located in BAMA (34º 34’S, 58º 31’W). Theprevailing meteorological conditions for each sampling period were analysed. Backward trajectories arrivingat the sampling site were obtained to explore the contributions from local and/or remote sources. Total,coarse and fine particle fractions were analysed by several techniques (gravimetry, scanning electronmicroscopy, PIXE (Particle Induced X-ray Emission) using 16O at 50 MeV energy, energy dispersive X-rayanalysis and X-ray diffraction, ion chromatography). The chemical and ion composition, besides morphologyand elemental composition allowed the identification of anthropogenic and natural sources as well ascontributions from remote regions. Aerosol composition measurements showed good correlation with themeteorological conditions and the possible source regions
    ENPROMER 2005 2nd Mercosur Congress on Chemical Engineering and 4th Mercosur Congress on Process Systems Engineering; 01/2005
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    ABSTRACT: Heterogeneous photocatalysis (HP) using UV/TiO 2 , photo-Fenton (PF) reaction using UV/Fe/H 2 O 2 and the combination UV/TiO 2 /Fe/ H 2 O 2 (HP–PF) were tested as processes to degrade oxalic acid (Ox) at relatively high concentrations (0.032 M). PF reactions were generally more efficient than HP including the reaction in the absence of H 2 O 2 . Oppositely to previous results (e.g., with EDTA), HP–PF combinations did not result, in the case of oxalate, better techniques for degradation than systems in the absence of TiO 2 . The kinetic behavior was not unique and two parameters were taken to evaluate the efficiency of each system: initial rates (R 0) and time to 95% of total mineralization (TOC 95). Addition of hydrogen peroxide improves the initial HP reaction rate and reduces TOC 95 . Addition of Fe 3+ also affects the reaction parameters but the effect of H 2 O 2 seems to be higher, at least under the present conditions. When both H 2 O 2 and iron were added simultaneously, the efficiency was higher. The optimal H 2 O 2 :Ox:Fe molar ratio was established and the results indicated that, at a fixed iron concentration, H 2 O 2 increased R 0 until a limit beyond which it did not cause any effect. No intermediates were formed in the reaction, oxalate being degraded directly to CO 2 . Analogies and differences with the EDTA system are presented. # 2005 Elsevier B.V. All rights reserved.
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    ABSTRACT: In this work, the comparison of 4-chlorophenol (4-CP) degradation by two different AOT processes has been performed: a) a homogeneous system with Fe(III)-NTA (1:1 complex), b) a TiO2/Fe(III)-NTA heterogeneous system. In both cases, NTA appears to play a positive role in the photochemical reaction. In the homogeneous system, the iron salt is the only absorbing species and is proved to be able to photoinduce 4-CP degradation ([4-CP] = 0.1-0.2 mM, [FeNTA] = 0.3-0.9 mM, pH 4, lambda = 365 nm). The progress of the reaction was positively affected by the FeNTA concentration, and the reaction kept going even after the total disappearance of FeNTA. However, 4-CP complete degradation requires the presence of oxygen, otherwise the reaction stops. In the heterogeneous system ([4-CP] = 2.0 mM, [FeNTA] = 1.0-2.0 mM, [TiO2] = 0.1 and 1.0 g L(-1), pH 3, lambda = 300-400 nm), an important effect of the complex on the degradation extent and on the initial reaction rate can be seen, which overcomes the effect of non-complexed Fe(III). This behaviour is more important at the highest TiO2 concentration.
    Water Science & Technology 02/2004; 49(4):123-8. · 1.10 Impact Factor
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    ABSTRACT: A complete study on the photocatalytic degradation of ethylenediaminetetraacetic acid (EDTA) over TiO2 has been initiated, to establish the influence of several parameters on the reaction rate, the nature of the intermediates and the kinetic regime. TiO2 (Degussa P25) suspensions containing EDTA at pH 3 at different concentrations were irradiated under near UV light. A Langmuirian behavior was observed, from which kinetic constants have been obtained. Experiments with 5.0 mM EDTA (zero order kinetic regime) were performed for 3 hours irradiation under different conditions. Under N2 bubbling, depletion of EDTA was very low. Under O2 bubbling, the concentration of EDTA decreased around 90%. However, the corresponding decrease of TOC ranged only between 4.5% and 9%. A higher TOC reduction (22% or more) was obtained by keeping the pH constant by HClO4 addition, or by hydrogen peroxide addition. Addition of 0.5 mM Fe(III) caused a dramatic increase on the initial rate of EDTA depletion and approximately a 32% TOC decrease. Analysis of the filtered solution was performed by ion chromatography and capillary electrophoresis to monitor the disappearance of EDTA and the formation of degradation products after different irradiation times. So far, glycine, ethylenediamine, formic acid, ammonium, iminodiacetic acid, oxalic acid and glyoxylic acid have been identified.
    Water Science & Technology 02/2001; 44(5):179-85. · 1.10 Impact Factor
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    ABSTRACT: The photocatalytic degradationof EDTA over TiO2 has been analyzed to establish the influence of oxidants on the reaction rate, the nature of the intermediates and the kinetic regime. Degussa P-25 suspensions containing EDTA at initial pH 3 in different concentrations were irradiated under near UV light. A Langmuirian behavior was observed. O2 at saturation concentrations was found to be crucial for EDTA degradation. The rapid depletion of EDTA was not accompanied by a corresponding TOC decrease, indicating formation of refractory intermediates. An enhancement in TOC reduction could be achieved by keeping pH constant or by hydrogen peroxide addition. Addition of Fe(III) caused a remarkable increase on the initial rate of EDTA consumption and also on TOC decrease. Changes in both parameters clearly increased under the simultaneous addition of Fe(III) and H2O2, until limiting values.
    International Journal of Photoenergy 01/2001; · 2.66 Impact Factor
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    ABSTRACT: The development of an analytical methodology for the specific determination of arsenite, arsenate and the organic species monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA), is described. The method is based on an ion chromatographic separation, coupled on-line to post-column generation of the gaseous hydrides by reaction with sodium tetrahydroborate in acidic medium. Detection and measurement were performed by inductively coupled plasma spectrometry operated in the atomic emission mode. Arsenic emission was monitored at 193.7 nm. Different types and sizes of anion-exchange columns, silica and polymeric, were tested using EDTA as eluent. Composition, acidity and flow-rate of the mobile phase were optimized in order to obtain the required resolution. Complete elution and resolution of the four species was achieved in about 6 min. Linear calibration curves were obtained in the 0.05-2 microg ml(-1) range for As(III), As(V) and MMA, and between 0.1 and 2.0 microg ml(-1) for DMA. The absolute limits of detection for 200-microl sample injections were in the ng range, with DMA the compound measured with less sensitivity. Results of the analyses of natural samples, such as river and ground waters spiked with the studied species, suggested that analyte recoveries might be dependent on the sample composition.
    Journal of Chromatography A 08/2000; 884(1-2):211-21. · 4.61 Impact Factor
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    ABSTRACT: The use of Eriochrome Black T in an alkaline, 40% methanol solution was found to be appropriate as post-column reagent for the determination of rare earths by ion chromatography. Detection of individual lanthanides and lanthanum was carried out at 512 nm and 650 nm after separation by dynamic cation exchange chromatography with gradient elution on C18 column and employing a solution containing alpha-hydroxyisobutiric acid/sodium octanesulfonate at pH 3.8 as eluent. The effect of the presence of micelles in the post-column reagent was studied. Sensitivities obtained by the addition of the cationic surfactants cetylpyridinium chloride (CPC) and hexadecyltrimethylammonium bromide (CTAB) were lower than those measured without surfactant addition. In some cases, the signal was totally suppressed. No change in sensitivity was observed with non-ionic (Triton X-100) or anionic (sodium dodecylsulphate, SDS) surfactants but a slight improvement in the baseline noise was observed with the SDS. An evaluation of the influence of chemical and operational variables on the post column reaction (PCR) reagent was carried out either by spectrophotometric tests or by chromatographic experiments. A comparison was performed between three PCR reagents: Eriochrome Black T and xylenol orange in the presence of a cationic surfactant and arsenazo III. Calibration response was linear up to an analyte concentration of 5.0 micrograms ml-1. Absolute detection limits lower than 7 and 17 ng were obtained at the detection wavelengths of 650 nm and 512 nm respectively, for all the natural lanthanides and lanthanum.
    Journal of Chromatography A 10/1999; 855(1):111-9. · 4.61 Impact Factor
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    ABSTRACT: The presence of the cationic surfactants cetylpyridinium chloride and hexadecyltrimethylammonium bromide in an alkaline 40% methanol medium was found to enhance sensitivity when xylenol orange is employed as the post-column reaction reagent for the determination of lanthanides by dynamic ion chromatography. Detection of individual lanthanides was carried out at 618 nm after separation by cation-exchange chromatography with gradient elution on a C18 column. The eluent was α-hydroxyisobutyric acid-sodium octanesulfonate, pH 3.8. Sensitivity enhancements by factors of three to six, compared with xylenol orange alone, were achieved at a cationic surfactant concentration of 2.4 mM. The calibration response was linear in the 0.05 to 5 μg ml−1 analyte concentration range. Limits of detection below 3 ng were obtained for all the natural lanthanides and lanthanum. No sensitivity enhancement effects were observed with anionic (sodium dodecyl sulfate) and non-ionic (Triton X-100) surfactants under the conditions tested.
    Journal of Chromatography A 01/1997; 770(1):75-83. · 4.61 Impact Factor
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    ABSTRACT: The chelating agent 1,2-diaminocyclohexanetetraacetic acid (DCTA) was tested as an eluent for the separation and determination of inorganic anions (Cl−, NO3−, CO42−) and some selected metals using single-column ion chromatography with ultraviolet detection. The effects of pH and eluent concentration on retention times for the system were studied to overview the possibilities of attaining optimum separations. The metals studied included Fe(III), Cr(III), Y(III), La(III), Nd(III), Gd(III), Ba(II), Ca(II), Cd(II), Co(II), Cu(II), Hg(II), Mg(II), Ni(II), Pb(II), Sr(II), Zn(II) and Mo(VI). The detection limits were generally below 0.5 μg ml−1. Results for the analysis of synthetic samples and drinking water are presented.
    Journal of Chromatography A - J CHROMATOGR A. 01/1995; 706(1):115-119.
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    ABSTRACT: A precise and rapid procedure for the determination of metallic macro-components in ceramic superconductor samples of the LaSrCuO type is described. Lanthanum, strontium and copper are determined by ion chromatography using a complexing mobile phase (EDTA solution) and UV detection. Calibration graphs were linear in the concentration ranges 0.4–100, 0.1–100 and 0.05–100 μg ml−1, respectively, and practical determination limits of 0.1, 0.04 and 0.025 μg ml−1 of La(III), Sr(II), Cu(II) ions, respectively, were achieved.
    Analytica Chimica Acta. 01/1993; 283(1):350-353.
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    ABSTRACT: Degradation of citric acid (Cit) at relatively high concentrations by photocatalysis over TiO 2 under air bubbling and near UV-light was tested under different conditions. The reaction was improved by addition of H 2 O 2 , Fe(III) or both. Minor amounts of H 2 O 2 were effective to enhance the oxidation and the mineralization. H 2 O 2 addition impacts more on the initial rate, while the effect of Fe(III) is more important after prolonged irradiation. The kinetic profiles were analyzed and compared, and the best ratio of reagents was found (1:1:1 H 2 O 2 /Cit/Fe molar ratio). However, a lower amount of Fe (1:1:0.2 H 2 O 2 /Cit/Fe ratio) was also effective. Similar experiments under the optimal conditions in the absence of TiO 2 were performed for comparison. When both H 2 O 2 and Fe(III) were present, the behavior with and without TiO 2 was very similar. So far, 3-oxoglutaric acid was detected as a reaction intermediate. A mechanistic analysis is initiated to explain some features of these complex systems.