RESUMEN
The thermoxidation of biodiesel was monitored using different spectroscopic techniques: UV-Vis and MIR absorption, Raman spectroscopy, and visible fluorescence. As the oxidation progressed, the UV-Vis absorption spectra showed an increase in the spectral range between 34,000 and 26,000â¯cm-1, while two main fluorescence bands (under ultraviolet excitation) were observed at around 21,000 and 15,000â¯cm-1. The UV-Vis absorption and fluorescence intensities presented opposite behavior during the processes, irrespective of the temperature used (90, 140, or 190⯰C). These effects could be explained by the consumption of natural antioxidants, followed by the formation of primary oxidation compounds. The Raman and MIR absorption results indicated the existence of a cis-trans isomerization effect, followed by the formation of hydroperoxides during the oxidation, with the behavior being the same as that revealed by the UV-Vis absorption and fluorescence analyses. The comparison, under the same conditions, of different spectroscopy techniques that can be used to monitor the stages of thermoxidation of soybean biofuel provides important information for selection of an appropriate technique for evaluating biodiesel integrity.
Asunto(s)
Biocombustibles/análisis , Glycine max/química , Calor , Espectrometría de Fluorescencia/métodos , Espectrofotometría Ultravioleta/métodos , Espectrometría Raman/métodos , Oxidación-ReducciónRESUMEN
We have been able to discriminate different castes and sexes of ants in the same colony by measuring cuticular hydrocarbon levels with Fourier transform infrared photoacoustic spectroscopy, compared by canonical discriminant function analysis. We have now applied this methodology to various colonies of two species of ants of the genus Ectatomma in the Brazilian Cerrado. There were clear interspecific differences in cuticular hydrocarbons of these ants, with a small intraspecific variation. The differences between colonies were greater in E. brunneum than in E. vizottoi. Genetic differences among the colonies and species were well estimated by Fourier transform infrared photoacoustic spectroscopy and statistical analyses.
Asunto(s)
Hormigas/química , Hidrocarburos/análisis , Proteínas de Insectos/química , Animales , Brasil , Proteínas de Insectos/análisis , Especificidad de la Especie , Espectroscopía Infrarroja por Transformada de Fourier/métodosRESUMEN
We have been able to discriminate different castes and sexes of ants in the same colony by measuring cuticular hydrocarbon levels with Fourier transform infrared photoacoustic spectroscopy, compared by canonical discriminant function analysis. We have now applied this methodology to various colonies of two species of ants of the genus Ectatomma in the Brazilian Cerrado. There were clear interspecific differences in cuticular hydrocarbons of these ants, with a small intraspecific variation. The differences between colonies were greater in E. brunneum than in E. vizottoi. Genetic differences among the colonies and species were well estimated by Fourier transform infrared photoacoustic spectroscopy and statistical analyses.