A resonance ionization detector (RID) based on the two-step laser-enhanced ionization of Mg in a ... more A resonance ionization detector (RID) based on the two-step laser-enhanced ionization of Mg in a miniature air–acetylene flame is described. The detector utilizes the 285.213 nm resonance absorption of Mg as the signal transition, i.e., photons to be measured. Magnesium atoms excited by absorption of photons at 285.2 nm were further excited to higher lying energy states by absorption of photons at 571.2 or 435.2 nm, from which collisional ionization could occur, or by absorption of photons at 300.9 nm, which directly ionized the excited Mg atoms via an autoionizing level above the ionization continuum. The miniature flame used (about 2 mm in diameter) had very low noise characteristics and the minimum detectable number of photons (MDP) was limited, in some instances, by the noise of the transimpedance amplifier used. The lowest MDP, obtained for the excitation scheme 3s21S (285.2 nm)→3p 1P0(435.2 nm)→6d 1D, was experimentally determined to be 1 × 103(7 × 10–16 J). The quantum efficiency of this excitation scheme, defined as the number of electrons created per photon absorbed at the signal transition (285.2 nm), was found to be 0.75. The spectral response bandwidth of the detector in the signal transition was determined to be mostly Lorentzian in nature, owing to pressure broadening in the atmospheric pressure flame, with a stray light rejection ratio of approximately 1 × 10–5 at 100 cm–1 displacement from the absorption maximum of the RID at 285.213 nm. An application of the RID is given in the detection of weak Raman scatter of carbon tetrachloride, chloroform and dimethyl sulfoxide.
The growing demand for high-purity quartz in the international market led to the systematic inves... more The growing demand for high-purity quartz in the international market led to the systematic investigation of the geochemical quality of this mineral in deposits Argentina. This study is a contribution to the scarce information on the geochemistry of quartz in Argentina. A total of 525 multielemental chemical analyses were performed with XRF spectrometry in less than 3 months. SiO2 concentration was calculated by difference from XRF impurity determinations. As a result of this study, 36 sites over 141 sampled deposits were identified as being of desirable quality. Low-Z oxides, considered critical impurities for quartz, were determined by atomic absorption spectrometry, only in samples of these selected sites, because of high XRF detection limits. The analytical results allowed the classification of the quality of quartz according to its environment and geological genesis. It could be determined that better purity quartz corresponds to veins far away from the Achala and Alpa Corral batholith and occurs in metamorphic rocks, followed by pegmatitic quartz from inside the batholith and lastly by quartz of well-known hydrothermal origin. Copyright 2004 John Wiley & Sons, Ltd.
Berichte Der Bunsengesellschaft Fur Physikalische Chemie, Nov 1, 1990
The quenching of the spin-orbit excited state of iodine atoms (I*) by ozone was measured in a fla... more The quenching of the spin-orbit excited state of iodine atoms (I*) by ozone was measured in a flash photolysis system monitoring the resonant absorption of I* at 206.2 nm. A quenching rate constant of (1.1 ± 0.1) · 10−11 cm3 s−1 was obtained at 300 K. This high value implies a reactive channel leading to the production of IO + O2. Indirect experimental observations confirm the presence of the latter species after the flash. A comparison of the present results with the reaction involving the fundamental state of atomic iodine is made. A strong spin-orbit effect is found. The rate constant for the quenching by O2 was also measured yielding a value of (2.7 ± 0.3) · 10−11 cm3 s−1.
International Journal of Environmental Analytical Chemistry, 2000
A phase-resolved luminescence system based on the use of a light emitting diode (LED) is applied ... more A phase-resolved luminescence system based on the use of a light emitting diode (LED) is applied to the trace determination of uranyl ion (UO2 ). The system performance is evaluated, phase resolved spectra of UO2 are shown as well as its lifetime determination using multifrequency phase resolved measurements. Analytical figures of merit are also presented for this system. A limit
Journal of the Chemical Society Faraday Transactions 2
The quenching of electronically excited iodine atoms l(2P1/2 ≡ I* ) by CH3 CN, CD3 CN, HCN, C2 H5... more The quenching of electronically excited iodine atoms l(2P1/2 ≡ I* ) by CH3 CN, CD3 CN, HCN, C2 H5 CN, and (CN)2 was studied. Good agreement was found for I* deactivation by acetonitrile and perdeuteroacetonitrile using two widely different techniques, namely time-resolved atomic absorption (TRAA) and chemical laser threshold gain (CLTG). The kinetic isotope effect determined, kH/ kD, was 2.2 ± 0.5 for both methods. This low value would support the existence of a noticeable reactive path and a possible channel assisted by a curve-crossing mechanism. Values here reported for the second-order rate constants for r* deactivation are, respectively, (1.2± 0.1)x10-13, (5.3±0.5)xl0-14, (3.3±0.2)x10-14, (1.3±0.1)x10-13, (2.2± 0.2) x 10-15 cm3 molecule-1 s-1 for CH3 CN, CD3 CN, HCN, C2 H5 CN and (CN)2, according to the TRAA method. Results from CLTG measurements are (1.6±0.1) x 10-13, (7.3±0.2)x 10-14 and (8.3±0.1)x 10-14 cm3 molecule -1 s-1 for CH3 CN, CD3 CN and HCN, respectively.
A graphite furnace is used to atomize samples which are transferred in an argon carrier gas to a ... more A graphite furnace is used to atomize samples which are transferred in an argon carrier gas to a low noise miniflame laser enhanced ionization detection system. Two step excitation is provided by dual Nd:YAG pumped dye lasers operating at 30 Hz. The limiting noise is 6 fC and the ionization yields near 0.8. Detection limits for Mg, Tl and In, limited by temporal probing inefficiencies and losses in sample transport, are ca. 10 fg.
RESUMEN Este trabajo presenta una experiencia de laboratorio destinada a que el alumno adquiera n... more RESUMEN Este trabajo presenta una experiencia de laboratorio destinada a que el alumno adquiera nociones básicas acerca de los conceptos de señal, ruido, error relativo, relación señal a ruido, y las aplique en la técnica de absorción UV-Vis para plantear estrategias destinadas a mejorarla calidad de la medición. Como parte de las actividades se analiza la variación de la relación señal a ruido para un conjunto de valores de absorbancia. En base a estas experiencias se puede deducir cuál es la fuente dominante de ruido para un determinado nivel de señal. Para la realización del práctico se puede utilizar cualquier espectrofotómetro que permita obtener en una forma sencilla la señal de absorción y su correspondiente ruido. Palabras claves: espectroscopía, absorción UV-Visible, relación señal a ruido
The objective of this research was to investigate the development of a reliable fingerprint from ... more The objective of this research was to investigate the development of a reliable fingerprint from elemental and isotopic signatures of Argentinean honey to assess its geographical provenance. Honey, soil, and water from three regions (Córdoba, Buenos Aires, and Entre Rı́os) were collected. The multielemental composition was determined by ICP-MS. δ(13)C was measured by isotopic ratio mass spectrometry, whereas the (87)Sr/(86)Sr ratio was determined using thermal ionization mass spectrometry. The data were analyzed by chemometrics looking for the association between the elements, stable isotopes, and honey samples from the three studied areas. Honey samples were differentiated by classification trees and discriminant analysis using a combination of eight key variables (Rb, K/Rb, B, U, (87)Sr/(86)Sr, Na, La, and Zn) presenting differences among the studied regions. The application of canonical correlation analysis and generalized procrustes analysis showed 91.5% consensus between soil, water, and honey samples, in addition to clear differences between studied areas. To the authors' knowledge, this is the first report demonstrating the correspondence between soil, water, and honey samples using different statistical methods, showing that elemental and isotopic honey compositions are related to soil and water characteristics of the site of origin.
Journal of the Chemical Society, Faraday Transactions 2, 1989
... Raul G. Badini, Leonor E. Pasteris, Gustavo A. Arguello* and Eduardo H. Staricco ( INFIQC), D... more ... Raul G. Badini, Leonor E. Pasteris, Gustavo A. Arguello* and Eduardo H. Staricco ( INFIQC), Departamento de Fisico-quimica, Facultad de Ciencias Quimicas, Universidad Nacional de Co'rdoba. ... Phys., 1984,81, 1337; (b) RJ Donovan and HM Gillespie, Chem. Phys. ...
The main goal of this study was to propose a reliable method to verify the geographical origin of... more The main goal of this study was to propose a reliable method to verify the geographical origin of meat, establishing the influence of soil and water on its isotopic and elemental composition. Thus, beef meat, soil, and water samples were collected from three major cattle-producing regions of Argentina (Buenos Aires, Córdoba, and Entre Ríos). Multielemental composition was determined on these three matrices by inductively coupled plasma mass spectrometry (ICP-MS), δ(13)C and δ(15)N by isotope-ratio mass spectrometry (IRMS), and the (87)Sr/(86)Sr ratio by thermal ionization mass spectrometry (TIMS). Soil and drinking water samples could be characterized and clearly differentiated by combining the isotopic ratios and elements, demonstrating differences in geology and climatic conditions of three regions. Similarly, meat originating at each sampling area was characterized and differentiated using only five key variables (Rb, Ca/Sr, δ(13)C, δ(15)N, and (87)Sr/(86)Sr). Generalized procrustes analysis (GPA), using the three studied matrices (soil, water, and meat) shows consensus between them and clear differences between studied areas. Furthermore, canonical correlation analysis (CCA) demonstrates significant correlation between the chemical-isotopic profile of meat with those corresponding to both soil and water (r(2) = 0.93, p < 0.001; and r(2) = 0.83, p < 0.001, respectively). So far, there are clear coincidences between the meat fingerprint and those from soil/water where cattle grew, presenting a good method to establish beef provenance. To the authors' knowledge this is the first report linking the influence of soil and water all together on the composition of beef, presenting the basis for the authentication of Argentinean beef, which could be extended to meat from different provenances.
A resonance ionization detector (RID) based on the two-step laser-enhanced ionization of Mg in a ... more A resonance ionization detector (RID) based on the two-step laser-enhanced ionization of Mg in a miniature air–acetylene flame is described. The detector utilizes the 285.213 nm resonance absorption of Mg as the signal transition, i.e., photons to be measured. Magnesium atoms excited by absorption of photons at 285.2 nm were further excited to higher lying energy states by absorption of photons at 571.2 or 435.2 nm, from which collisional ionization could occur, or by absorption of photons at 300.9 nm, which directly ionized the excited Mg atoms via an autoionizing level above the ionization continuum. The miniature flame used (about 2 mm in diameter) had very low noise characteristics and the minimum detectable number of photons (MDP) was limited, in some instances, by the noise of the transimpedance amplifier used. The lowest MDP, obtained for the excitation scheme 3s21S (285.2 nm)→3p 1P0(435.2 nm)→6d 1D, was experimentally determined to be 1 × 103(7 × 10–16 J). The quantum efficiency of this excitation scheme, defined as the number of electrons created per photon absorbed at the signal transition (285.2 nm), was found to be 0.75. The spectral response bandwidth of the detector in the signal transition was determined to be mostly Lorentzian in nature, owing to pressure broadening in the atmospheric pressure flame, with a stray light rejection ratio of approximately 1 × 10–5 at 100 cm–1 displacement from the absorption maximum of the RID at 285.213 nm. An application of the RID is given in the detection of weak Raman scatter of carbon tetrachloride, chloroform and dimethyl sulfoxide.
The growing demand for high-purity quartz in the international market led to the systematic inves... more The growing demand for high-purity quartz in the international market led to the systematic investigation of the geochemical quality of this mineral in deposits Argentina. This study is a contribution to the scarce information on the geochemistry of quartz in Argentina. A total of 525 multielemental chemical analyses were performed with XRF spectrometry in less than 3 months. SiO2 concentration was calculated by difference from XRF impurity determinations. As a result of this study, 36 sites over 141 sampled deposits were identified as being of desirable quality. Low-Z oxides, considered critical impurities for quartz, were determined by atomic absorption spectrometry, only in samples of these selected sites, because of high XRF detection limits. The analytical results allowed the classification of the quality of quartz according to its environment and geological genesis. It could be determined that better purity quartz corresponds to veins far away from the Achala and Alpa Corral batholith and occurs in metamorphic rocks, followed by pegmatitic quartz from inside the batholith and lastly by quartz of well-known hydrothermal origin. Copyright 2004 John Wiley & Sons, Ltd.
Berichte Der Bunsengesellschaft Fur Physikalische Chemie, Nov 1, 1990
The quenching of the spin-orbit excited state of iodine atoms (I*) by ozone was measured in a fla... more The quenching of the spin-orbit excited state of iodine atoms (I*) by ozone was measured in a flash photolysis system monitoring the resonant absorption of I* at 206.2 nm. A quenching rate constant of (1.1 ± 0.1) · 10−11 cm3 s−1 was obtained at 300 K. This high value implies a reactive channel leading to the production of IO + O2. Indirect experimental observations confirm the presence of the latter species after the flash. A comparison of the present results with the reaction involving the fundamental state of atomic iodine is made. A strong spin-orbit effect is found. The rate constant for the quenching by O2 was also measured yielding a value of (2.7 ± 0.3) · 10−11 cm3 s−1.
International Journal of Environmental Analytical Chemistry, 2000
A phase-resolved luminescence system based on the use of a light emitting diode (LED) is applied ... more A phase-resolved luminescence system based on the use of a light emitting diode (LED) is applied to the trace determination of uranyl ion (UO2 ). The system performance is evaluated, phase resolved spectra of UO2 are shown as well as its lifetime determination using multifrequency phase resolved measurements. Analytical figures of merit are also presented for this system. A limit
Journal of the Chemical Society Faraday Transactions 2
The quenching of electronically excited iodine atoms l(2P1/2 ≡ I* ) by CH3 CN, CD3 CN, HCN, C2 H5... more The quenching of electronically excited iodine atoms l(2P1/2 ≡ I* ) by CH3 CN, CD3 CN, HCN, C2 H5 CN, and (CN)2 was studied. Good agreement was found for I* deactivation by acetonitrile and perdeuteroacetonitrile using two widely different techniques, namely time-resolved atomic absorption (TRAA) and chemical laser threshold gain (CLTG). The kinetic isotope effect determined, kH/ kD, was 2.2 ± 0.5 for both methods. This low value would support the existence of a noticeable reactive path and a possible channel assisted by a curve-crossing mechanism. Values here reported for the second-order rate constants for r* deactivation are, respectively, (1.2± 0.1)x10-13, (5.3±0.5)xl0-14, (3.3±0.2)x10-14, (1.3±0.1)x10-13, (2.2± 0.2) x 10-15 cm3 molecule-1 s-1 for CH3 CN, CD3 CN, HCN, C2 H5 CN and (CN)2, according to the TRAA method. Results from CLTG measurements are (1.6±0.1) x 10-13, (7.3±0.2)x 10-14 and (8.3±0.1)x 10-14 cm3 molecule -1 s-1 for CH3 CN, CD3 CN and HCN, respectively.
A graphite furnace is used to atomize samples which are transferred in an argon carrier gas to a ... more A graphite furnace is used to atomize samples which are transferred in an argon carrier gas to a low noise miniflame laser enhanced ionization detection system. Two step excitation is provided by dual Nd:YAG pumped dye lasers operating at 30 Hz. The limiting noise is 6 fC and the ionization yields near 0.8. Detection limits for Mg, Tl and In, limited by temporal probing inefficiencies and losses in sample transport, are ca. 10 fg.
RESUMEN Este trabajo presenta una experiencia de laboratorio destinada a que el alumno adquiera n... more RESUMEN Este trabajo presenta una experiencia de laboratorio destinada a que el alumno adquiera nociones básicas acerca de los conceptos de señal, ruido, error relativo, relación señal a ruido, y las aplique en la técnica de absorción UV-Vis para plantear estrategias destinadas a mejorarla calidad de la medición. Como parte de las actividades se analiza la variación de la relación señal a ruido para un conjunto de valores de absorbancia. En base a estas experiencias se puede deducir cuál es la fuente dominante de ruido para un determinado nivel de señal. Para la realización del práctico se puede utilizar cualquier espectrofotómetro que permita obtener en una forma sencilla la señal de absorción y su correspondiente ruido. Palabras claves: espectroscopía, absorción UV-Visible, relación señal a ruido
The objective of this research was to investigate the development of a reliable fingerprint from ... more The objective of this research was to investigate the development of a reliable fingerprint from elemental and isotopic signatures of Argentinean honey to assess its geographical provenance. Honey, soil, and water from three regions (Córdoba, Buenos Aires, and Entre Rı́os) were collected. The multielemental composition was determined by ICP-MS. δ(13)C was measured by isotopic ratio mass spectrometry, whereas the (87)Sr/(86)Sr ratio was determined using thermal ionization mass spectrometry. The data were analyzed by chemometrics looking for the association between the elements, stable isotopes, and honey samples from the three studied areas. Honey samples were differentiated by classification trees and discriminant analysis using a combination of eight key variables (Rb, K/Rb, B, U, (87)Sr/(86)Sr, Na, La, and Zn) presenting differences among the studied regions. The application of canonical correlation analysis and generalized procrustes analysis showed 91.5% consensus between soil, water, and honey samples, in addition to clear differences between studied areas. To the authors' knowledge, this is the first report demonstrating the correspondence between soil, water, and honey samples using different statistical methods, showing that elemental and isotopic honey compositions are related to soil and water characteristics of the site of origin.
Journal of the Chemical Society, Faraday Transactions 2, 1989
... Raul G. Badini, Leonor E. Pasteris, Gustavo A. Arguello* and Eduardo H. Staricco ( INFIQC), D... more ... Raul G. Badini, Leonor E. Pasteris, Gustavo A. Arguello* and Eduardo H. Staricco ( INFIQC), Departamento de Fisico-quimica, Facultad de Ciencias Quimicas, Universidad Nacional de Co'rdoba. ... Phys., 1984,81, 1337; (b) RJ Donovan and HM Gillespie, Chem. Phys. ...
The main goal of this study was to propose a reliable method to verify the geographical origin of... more The main goal of this study was to propose a reliable method to verify the geographical origin of meat, establishing the influence of soil and water on its isotopic and elemental composition. Thus, beef meat, soil, and water samples were collected from three major cattle-producing regions of Argentina (Buenos Aires, Córdoba, and Entre Ríos). Multielemental composition was determined on these three matrices by inductively coupled plasma mass spectrometry (ICP-MS), δ(13)C and δ(15)N by isotope-ratio mass spectrometry (IRMS), and the (87)Sr/(86)Sr ratio by thermal ionization mass spectrometry (TIMS). Soil and drinking water samples could be characterized and clearly differentiated by combining the isotopic ratios and elements, demonstrating differences in geology and climatic conditions of three regions. Similarly, meat originating at each sampling area was characterized and differentiated using only five key variables (Rb, Ca/Sr, δ(13)C, δ(15)N, and (87)Sr/(86)Sr). Generalized procrustes analysis (GPA), using the three studied matrices (soil, water, and meat) shows consensus between them and clear differences between studied areas. Furthermore, canonical correlation analysis (CCA) demonstrates significant correlation between the chemical-isotopic profile of meat with those corresponding to both soil and water (r(2) = 0.93, p < 0.001; and r(2) = 0.83, p < 0.001, respectively). So far, there are clear coincidences between the meat fingerprint and those from soil/water where cattle grew, presenting a good method to establish beef provenance. To the authors' knowledge this is the first report linking the influence of soil and water all together on the composition of beef, presenting the basis for the authentication of Argentinean beef, which could be extended to meat from different provenances.
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