Publications by authors named "Gabriel Bilmes"

8 Publications

  • Page 1 of 1

Laser-Induced Breakdown Spectroscopy (LIBS) Quality Control and Origin Identification of Handmade Manufactured Cigars.

Appl Spectrosc 2015 Oct;69(10):1205-9

Centro de Investigaciones Opticas (CONICET-CICPBA), Camino Centenario e/505 y 508, 1897 La Plata, Argentina.

Tobacco is an agricultural product originating in America that is obtained by processing the leaves of various plants of the genus Nicotiana tabacum. It is the inedible product occupying the most plantings in the world, according to a recent report from the United Nations Food and Agriculture Organization. It is consumed in various ways, but the most popular form of consumption is, undoubtedly, by smoking cigarettes. A particular segment of the tobacco industry is the manufacturing of handmade cigars, which for some third-world countries is an important source of income. There are different qualities of cigars, and a major problem is the adulteration that occurs, for example, when authentic high-quality leaves are replaced by lower quality leaves. A factor that influences the quality of the cigars is the smoke combustion process, which depends on several factors, particularly the composition of the leaves. We present a simple and quick technique for the quality control and origin identification of handmade cigars that measures the Mg/Ca ratios in the tobacco leaves and wrappers of the cigars using laser-induced breakdown spectroscopy.
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http://dx.doi.org/10.1366/15-07935DOI Listing
October 2015

Application of laser-induced breakdown spectroscopy (LIBS) and neural networks to olive oils analysis.

Appl Spectrosc 2013 Sep;67(9):1064-72

Departamento de Química Analítica. Facultad de Ciencias Químicas, Universidad Complutense, 28040 Madrid, Spain.

The adulteration and traceability of olive oils are serious problems in the olive oil industry. In this work, a method based on laser-induced breakdown spectroscopy (LIBS) and neural networks (NNs) has been developed and applied to the identification, quality control, traceability, and adulteration detection of extra virgin olive oils. Instant identification of the samples is achieved using a spectral library, which was obtained by analysis of representative samples using a single laser pulse and treatment by NNs. The samples used in this study belong to four countries. The study also included different regions of each country. The results obtained allow the identification of the oils tested with a certainty of more than 95%. Single-shot measurements were enough for clear identification of the samples. The method can be developed for automatic real-time, fast, reliable, and robust measurements, and the system can be packed into portable form for non-specialist users.
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http://dx.doi.org/10.1366/12-06916DOI Listing
September 2013

Photophysical behavior of new acridine(1,8)dione dyes.

Photochem Photobiol Sci 2013 Nov;12(11):1968-75

Laboratorio de Espectroscopia Atómica y Molecular, Universidad Industrial de Santander, A.A. 678, Bucaramanga, Colombia.

The photophysical behavior of five acridine(1,8)dione dyes of biological interest was studied by absorption and fluorescence spectroscopy, photoacoustics and time resolved phosphorescence techniques. The results obtained in ethanol and acetonitrile solutions show that the main spectroscopic and photophysical parameters of these compounds depend strongly on both the solvent and oxygen concentrations. Oxygen completely quenched the triplet state of all dyes. In nitrogen-saturated solutions, quantum efficiencies of triplet formation in ethanol were lower than those in acetonitrile.
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http://dx.doi.org/10.1039/c3pp50159kDOI Listing
November 2013

Photoacoustic and luminescence characterization of nitrogen heterocyclic aromatic UV-MALDI matrices in solution.

Photochem Photobiol Sci 2012 Jun 23;11(6):1062-8. Epub 2012 Mar 23.

CIHIDECAR-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Pabellón II, 3 Ciudad Universitaria, (1428) Buenos Aires, Argentina.

A group of nitrogen heterocyclic aromatic compounds used, among others, as UV-MALDI matrices was studied. By using spectroscopic, luminescence and photoacoustic techniques, as well as time resolved phosphorescence for singlet oxygen production determination, the behaviour of 9-aminoacridine (9AA), 3-aminoquinoline (3AQ), 2-(2-aminoethylamino)-5-nitropyridine (AAN) and 3,4-dihydro-7-methoxy-1-methyl-9H-pyrido[3,4-b] indole (harmaline, HLA) in acetonitrile solutions is described. The results show that for these compounds radiationless processes that release prompt heat to the media are a quite important deactivation mechanism.
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http://dx.doi.org/10.1039/c2pp05388hDOI Listing
June 2012

A new method for relative Sr determination in human teeth enamel.

J Anthropol Sci 2011 1;89:153-60. Epub 2011 Jul 1.

Centro de Investigaciones Opticas, (CONICET La Plata, CIC), CC 124, 1900, La Plata, Argentina.

We present a new method to determine Sr/Ca changes in hard dental tissues based on laser ablation and spectroscopic detection. By using femtosecond Laser Induced Breakdown Spectroscopy (fs-LIBS), we micro mapped the relative amount of strontium in the enamel of three human lower third molar. We also analyzed the Sr/Ca ratio along the striae of Retzius. Results show that microlibs allows detection of variation in relative Sr/Ca ratio through enamel. The same values of Sr/Ca ratio were found along a single stria. The method has a precision better than 95% and is sensitive enough to detect Sr/Ca ratio variations among striae and within stria. Fs-LIBS generates information in a fast and simple way that can be used by non-specialists to make inferences about diet or mobility in human populations and fossil hominids.
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http://dx.doi.org/10.4436/jass.89012DOI Listing
April 2012

Comparative photophysical investigation of oxygen and sulfur as covalent linkers on octaalkylamino substituted zinc(II) phthalocyanines.

Photochem Photobiol Sci 2008 Jun 14;7(6):738-47. Epub 2008 Apr 14.

INQUIMAE-CONICET and Departamento de Química Inorgánica, Analítica y Química Física, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Ciudad Universitaria, Ciudad Autónoma de Buenos Aires, Argentina.

This work describes a systematic comparison of oxygen and sulfur as covalent linkers on octasubstituted zinc(II) phthalocyaninates. Most photophysical parameters that make phthalocyanines technologically relevant, e.g. molar absorption coefficients, fluorescence, triplet and singlet oxygen quantum yields, are essentially unaffected by the substitution. The energy content of the first triplet state was observed to be close to the first singlet state of molecular oxygen for both spacers, as follows from photoacoustic determinations. Nonetheless, a bathochromic shift of 30 nm in the absorption and emission maxima, and of 60 nm in the triplet-triplet absorption spectra were observed when alkyloxyl and alkylsulfanyl moieties were alternatively present. Fluorescence quantum yields proved to be much more sensitive towards aggregation than the absorption spectra. Therefore, a novel fluorescence data analysis provided aggregation parameters and photophysical properties of the monomeric species. It was observed that the tendency towards dimerization is slightly higher with sulfur linkers. These results set a foundation for the rational design of conveniently substituted phthalocyaninates with different connectors between the macrocycle and the side chains.
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http://dx.doi.org/10.1039/b802709aDOI Listing
June 2008

Identification and measurement of dirt composition of manufactured steel plates using laser-induced breakdown spectroscopy.

Appl Spectrosc 2004 Dec;58(12):1475-80

Centro de Investigaciones Opticas (CONICET-CIC) y Universidad Nacional de La Plata, Casilla de Correo 124, (1900) La Plata, Argentina.

Laser-induced breakdown spectroscopy (LIBS) was used for the characterization of the main components of the surface residual dirt produced in cold-rolled steel plates as a consequence of the manufacturing stages. At laser fluences between 0.05 J/cm(2) < F < 0.30 J/cm(2), dirt ablation takes place without any contribution from the substrate. Results show that the main components of the dirt are fine particles of Fe mostly homogeneously distributed in a thin layer of grease and soaps. In the primary stages of the manufacturing process carbon residuals can also be found. By measuring light emission from the lambda = 495.9 nm line of Fe(I) after laser ablation, we developed a real-time on-line method for the determination of the concentration of iron particles present in the surface dirt. The obtained results open new possibilities in the design of real-time instruments for industrial applications as a quality control of products and processes.
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http://dx.doi.org/10.1366/0003702042641425DOI Listing
December 2004

The photophysics of nitrocarbazoles studied by using spectroscopic, photoacoustic and luminescence techniques.

Photochem Photobiol Sci 2003 Jul;2(7):808-16

Centro de Investigaciones Opticas (CONICET-CIC), Casilla de Correo 124, (1900) La Plata, Argentina.

The photophysical behaviour of 1-nitrocarbazol and 3-nitrocarbazol in different organic solvents has been studied by using spectroscopic, luminescence and photoacoustic techniques. Absorption spectra and triplet state transient spectra were recorded and formation quantum yields and lifetimes determined. Phosphorescence emission at 77 K and laser induced luminescence in acetonitrile solution at 298 K for the nitrocarbazoles were studied. Results are discussed in terms of the optimized structure of 1-nitrocarbazole and 3-nitrocarbazole and compared with that of carbazole. The nitro group attached to the carbazole moiety induces important changes in the photophysical behavior of those compounds.
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http://dx.doi.org/10.1039/b304520jDOI Listing
July 2003