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by Keyword: Organic compounds


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Guamán, Ana V., Carreras, Alba, Calvo, Daniel, Agudo, Idoya, Navajas, Daniel, Pardo, Antonio, Marco, Santiago, Farré, Ramon, (2012). Rapid detection of sepsis in rats through volatile organic compounds in breath Journal of Chromatography B , 881-882, 76-82

Background: Sepsis is one of the main causes of death in adult intensive care units. The major drawbacks of the different methods used for its diagnosis and monitoring are their inability to provide fast responses and unsuitability for bedside use. In this study, performed using a rat sepsis model, we evaluate breath analysis with Ion Mobility Spectrometry (IMS) as a fast, portable and non-invasive strategy. Methods: This study was carried out on 20 Sprague-Dawley rats. Ten rats were injected with lipopolysaccharide from Escherichia coli and ten rats were IP injected with regular saline. After a 24-h period, the rats were anaesthetized and their exhaled breaths were collected and measured with IMS and SPME-gas chromatography/mass spectrometry (SPME-GC/MS) and the data were analyzed with multivariate data processing techniques. Results: The SPME-GC/MS dataset processing showed 92% accuracy in the discrimination between the two groups, with a confidence interval of between 90.9% and 92.9%. Percentages for sensitivity and specificity were 98% (97.5–98.5%) and 85% (84.6–87.6%), respectively. The IMS database processing generated an accuracy of 99.8% (99.7–99.9%), a specificity of 99.6% (99.5–99.7%) and a sensitivity of 99.9% (99.8–100%). Conclusions: IMS involving fast analysis times, minimum sample handling and portable instrumentation can be an alternative for continuous bedside monitoring. IMS spectra require data processing with proper statistical models for the technique to be used as an alternative to other methods. These animal model results suggest that exhaled breath can be used as a point-of-care tool for the diagnosis and monitoring of sepsis.

Keywords: Sepsis, Volatile organic compounds, Ion mobility spectrometer, Rat model, Bedside patient systems, Non-invasive detection


Oncins, Gerard, Vericat, Carolina, Sanz, Fausto, (2008). Mechanical properties of alkanethiol monolayers studied by force spectroscopy Journal of Chemical Physics , 128, (4), 044701

The mechanical properties of alkanethiol monolayers on Au(111) in KOH solution have been studied by force spectroscopy. The analysis of the vertical force versus penetration curves showed that monolayer penetration is a stepped process that combines elastic regions with sudden penetration events. The structural meaning of these events can be explained both by the creation of gauche defects on the hydrocarbon chains and by a cooperative molecular tilting model proposed by Barrena et al. [J. Chem. Phys. 113, 2413 (2000)]. The validity of these models for alkanethiol monolayers of different compactness and chain length has been discussed. The Young's modulus (E) of the monolayers has been calculated by using a recently developed model which considers the thickness of the monolayer as a parameter, thus allowing a decoupling of the mechanical properties of the thiol layer from those of the Au(111) substrate. As a result, the calculated E values are in the range of 50-150 Pa, which are remarkably lower than those previously reported in the literature.

Keywords: Adsorbed layers, AFM, Gold, Monolayers, Organic compounds, Self-assemblyYoung's modulus