Determination of sub-ppb epichlorohydrin levels in water by on-line solid-phase extraction liquid chromatography/tandem mass spectrometry

A new sensitive and selective method based on on-line solid-phase extraction (SPE) coupled to liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) using a triple quadrupole mass spectrometer has been developed for the determination of epichlorohydrin (ECH) in different types of water samples. ECH is not easily determined directly by ESI-MS as it is not readily ionized, and it has a low molecular mass and high polarity. Thus, prior derivatization of ECH was necessary, employing 3,5-difluorobenzylamine as a derivatizing agent with Fe(III) as a catalyst. In order to achieve accurate quantification, correcting for matrix effects, losses in the derivatization process and instrumental deviations, isotope labelled ECH (ECH-d(5)) was added as an internal standard (IS) to the water samples. The method was validated based on European SANCO guidelines using drinking and other types of treated water spiked at two concentration levels (0.1 and 1.0 microg/L), the lower level having been established as the limit of quantification (LOQ) of the method. Satisfactory accuracy (recoveries between 70 and 103%), precision (RSD 0.99) were obtained. The limit of detection (LOD) was set up at 0.03 microg/L. The method was applied to different water samples (drinking water and water samples collected from a municipal treatment water plant). In order to enhance confidence, five selected reaction monitoring (SRM) transitions were acquired, thus obtaining a simultaneous reliable quantification and identification of ECH in water, even at sub-ppb level

Relaci?n del grado de cumplimiento de gobierno corporativo en la rentabilidad y costo de la deuda financiera en las empresas mineras del Per? que cotizan en la BVL durante los a?os 2014-2018

La implementaci?n de pr?cticas de gobierno corporativo trae consigo mejoras en la gesti?n, generan eficiencia y a?aden valor a las empresas y hoy es un tema relevante en las empresas del mundo debido a los problemas de agencia y de asimetr?a de informaci?n que se han intensificado por la formaci?n de grandes empresas, por la separaci?n de la propiedad y la gesti?n. En el Per?, el gobierno corporativo se ha vuelto relevante por una necesidad de mayor transparencia y divulgaci?n de la informaci?n necesaria para la toma de decisiones y nos hemos centrado en el sector miner?a debido a la importancia econ?mica del pa?s

Gravitational Smearing of Minimal Supersymmetric Unification Predictions

A short and mean paper.Comment: 10 pages total + 1 postscript figure (included), revised: all lines are TRULY < 70 characters long (try it!); LBL-32905, UCB-PTH-92/3

Life history and production of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) in the lower Ebro river: a comparison after 18 years. Aquat Insects 2008; 30

The life history of the burrowing mayfly Ephoron virgo (Olivier, 1791) (Ephemeroptera: Polymitarcyidae) was studied during spring and summer 2005 in the lower Ebro river (Catalonia) and compared to a previous study performed in 1987 (Iba´n˜ez, Escosa, Mun˜oz an

Cinco momentos de arquitectura y urbanismo: El Banco de la Rep?blica en Ibagu?, 1925-1992.

135 p.La historia de la arquitectura y el urbanismo del Banco de la Rep?blica en Ibagu? consta de cinco momentos en los que la entidad configur? uno de los sistemas de espacio p?blico y calidad arquitect?nica m?s relevantes de la ciudad. ?C?mo se realizaron estas transformaciones? Aqu? se presenta desde el primer edificio Art D?co en la ciudad historicista, a principios del siglo XX, hasta los procesos de financiaci?n de la infraestructura del ferrocarril del Tolima, las plazas de mercado, el edificio indigenista que reemplaz? al colegio de San Sim?n, la plazoleta y el centro cultural Dar?o Echand?a