Estimation of comprehensive two-dimensional gas chromatographic response from one-dimensional gas chromatography data

Trabajo presentado a la XV Reunión Científica de la Sociedad Española de Cromatografía y Técnicas Afines (SECyTA) celebrada en Castellón de la Plana del 28 al 30 de octubre de 2015Optimization of a separation in comprehensive two-dimensional gas chromatography (GC×GC) requires the selection of an appropriate set column, and the optimisation of their respective dimensions, temperature programs and flow rates. Until not so long ago, a time consuming trial and error process was the only way to select the columns and chromatographic conditions for the two GC dimensions. During the last few years, several attempts have been proposed to estimate the chromatographic response in GC×GC [1-4]. Although most of these methods are helpful contributions, some of them focussed exclusively on the retention time estimation and do not consider the effect of peak width, also essential for a correct prediction of the chromatographic separation capability. Others are based on theoretical formulas not applicable to the extreme experimental conditions used in GC×GC, or are only valid for specific types of compounds or stationary phases: these models cannot be corrected for different separation problems. In this work, modelization of retention time and peak width has been carried out from experimental 1D GC data in order to estimate the response in GC×GC separation for different column sets operated under different flows and temperatures. Several theoretical and experimental models are proposed for estimation of 1D and 2D retention time and peak width; in experimental models, 1D GC data are required together with information on column characteristics and operation conditions. Models for hold-up time, retention factor and peak width were first validated in 1D GC from the fit between experimental and calculated data. Their validation in GC×GC was carried out by using n-alkanes and a mixture of disaccharides as their trimethylsilyl oxime derivatives. Comparison of experimental and estimated data showed good results for retention time in both first and second dimension. Peak widths presented, however, some errors, caused by the no consideration on estimation of the effect of the modulator or the rather unusual chromatographic conditions used. The developed programme is very versatile as it can be used for the calculation of the chromatographic response of compounds with different polarity and volatility, analysed under different pressures and temperature ramps, and with different sets of columns. [1] J.V. Seeley, E.M. Libby, K.A.H. Edwards, S.K. Seeley, J. Chromatogr. A 1216 (2009) 1650. [2] F.L. Dorman, P.D. Schettler, L.A. Vogt, J.W. Cochran, J. Chromatogr. A 1186 (2008) 196. [3] Y. Zhao, J. Zhang, B. Wang, S.H. Kim, A. Fang, B. Bogdanov, Z. Zhou, C. McClain, X. Zhang, J. Chromatogr. A 1218 (2011) 2577. [4] S. Zhu, S. He, D.R. Worton, A.H. Goldstein, J. Chromatogr. A 1233 (2012) 147. Acknowledgements: This work has been funded by Ministerio de Economía y Competitividad (project CTQ2012-32957), Comunidad Autónoma de Madrid (Spain) and European funding from FEDER program (AVANSECAL-CM S2013/ABI-3028) and Fundación Ramón Areces. ACS thanks Ministerio de Economía y Competitividad of Spain for a Ramón y Cajal contract.CTQ2012-32957Peer reviewe

Columnas capilares para la separación de enantiómeros en cromatografía de gases

Referencia OEPM: P200001452.-- Fecha de solicitud: 08/06/2000.-- Titular: Consejo Superior de Investigaciones Científicas (CSIC).Columnas capilares para la separación de enantiómeros en cromatografía de gases. Las columnas constan de un tubo de sílice vítrea, vidrio (puede ser tipo borosilicato, o bien sodocálcico u otro) o algún material similar en cuanto a características de composición, inercia química, y propiedades mecánicas. El tubo de sílice vítrea va recubierto externamente de poliimida para reforzar su estabilidad a la rotura. La longitud práctica de los tubos oscila entre 10 y 50 m de longitud, pudiendo variar entre 1 m y 200 m; el diámetro interno suele variar entre 0.1 y 0.5 mm. Las etapas más novedosas del producto son el tratamiento de la superficie interna del tubo capilar y la fase mixta empleada. El objeto de esta patente es la fabricación este tipo de columnas capilares son aptas para la separación de enantiómeros por cromatografía de gases.Peer reviewe

Comparative analysis of the alkyl breakdown products from soil humic acids by thermal and wet chemical degradation methods

6 pages. Comunicación presentada al citado simposio, celebrado del 17-20 de septiembre, 2002, en Leoben (Austria).Total amounts and distribution patterns of alkyl degradation compounds were analyzed in soil humic acids isolated from a variety of continental Mediterranean ecosystems in Central Spain. Soil physical and chemical characteristics, humic acid composition and biomarker assemblages were studied in 16 representative, undisturbed or degraded forest ecosystems including broad-leaved autochthonous forests, bush formations, cultures, pastures and pine forests. The humic acid fraction of these soils was previously characterized by routine spectroscopic methods (UV-visible, FTIR, 13C and 15N CPMAS NMR). In the present study qualitative and quantitative features of the alkyl domain of humic acids are examined by comparing the structural information provided by independent destructive techniques, with special emphasis on the mild alkaline degradation (sodium perborate) and thermal degradation by Curie-point pyrolysis.Peer reviewe

Comportamiento al cultivo experimental en Aragón de Lippia alba para la normalización de la materia prima obtenida

Dentro de un amplio proyecto de normalización de productos naturales obtenidos de especies de la flora aromática latinoamericana, en el presente trabajo se presenta el estudio del comportamiento de los tres años iniciales de adaptación a cultivo de la especie Lippia alba (Fam. Verbenáceas), en diferentes condiciones agroclimáticas dentro la Comunidad Autónoma de Aragón. El material vegetal procedía de dos quimiotipos correspondientes a poblaciones de Uruguay y Costa Rica. La experimentación se realizó en parcelas de ensayo en Teruel y Ejea de los Caballeros (Zaragoza, España). La respuesta de adaptación a las zonas ensayadas ha sido diferente para cada uno de los quimiotipos estudiados. Ninguno de los dos ha soportado las condiciones agroclimáticas de la zona de Teruel, mientras que en Ejea de los Caballeros solamente se ha adaptado el quimiotipo Uruguay. El factor limitante ha sido fundamentalmente las bajas temperaturas durante los meses de invierno. Se ha realizado un seguimiento para cada espécimen de planta en cada una de las fases del cultivo con tratamiento individualizado planta a planta con el fin de comprobar su grado de selección. La biomasa producida ha proporcionado muestras normalizadas para comprobar su respuesta en materia seca y aceite esencial. El aceite esencial se ha obtenido por dos diferentes métodos de extracción, hidrodestilación y con dióxido de carbono supercrítico. Asimismo, se ha efectuado la analítica de los extractos obtenidos de las plantas en estudio. Químicamente, se ha confirmado el mantenimiento de las características del quimiotipo adaptado al cultivo en Aragón

Annex Troubleshooting

The chapter provides some typical examples of chromatograms and contour plots where some of the most common problems of GCxGC can visually be identified. These problems are explained and the most plausible practical solutions are described. The high speed and the special requirements of the 2D separation, the GCxGC transfer process becomes particularly delicate or prone to problems during method development. Peak shape and eventually GCxGC resolution are affected by both categories of parameters. The types of troubleshooting observed in GCxGC are chromatographic peak distortion and analyte degradation, programmed temperature separations, wraparound, and modulation process. Low programming temperature rates of the 1D column can result in widening of the chromatographic peak, which in addition can show a typical asymmetry (tailing peak) derived from extra column effects and from active points in the column. In GCxGC, slow temperatures ramps should be preferred when working with oven programmed temperature because the application of fast oven temperature ramps can adversely affect the possible 2D structure and peak shape visualization in the contour plot as well as the separation itself. Wraparound occurs when the retention time of a compound in the 2D column exceeds the modulation period. It can be identified in the 2D profile by the elution of the affected compound during the subsequent modulation cycle(s). The enhanced separation power provided by GCxGC can partially be lost if the resolution achieved in the first dimension is not preserved during modulation and separation in the second dimension.Peer reviewe

Aislamiento y caracterización de la fracción húmina del suelo mediante despolimerización con perborato de sodio

1 página, 1 figura. Ponencia presentada a la IX Bienal de la Real Sociedad Española de Historia Natural. Sevilla, 25-30 de septiembre, 1989.La imposibi1idad de aislar cuantitativatente la húmina de los suelos (fracción orgánica insoluble a todos los valores de pH) en un estado de alteración aceptab1e ha supuesto una gran limitación en los estudios sobre su naturaleza química.Peer reviewe

Plantas y cultura: análisis químico de extractos naturales con actividad microbicida e insecticida. Aplicaciones a materiales históricos con biodeterioro.

Trabajo presentado en el Simposio Medio Ambiente en Museos. Tecnologías sostenibles para la preservación de colecciones de arte contemporáneo, celebrado en el Museo de Arte Reina Sofía (Madrid) los días 15, 16 y 17 de junio de 2015.Comunidad Autónoma de Madrid (Spain) and European funding from FEDER program (AVANSECAL-CM S2013/ABI-3028)Peer reviewe

Presence of some cyclitols in honey

Quercitol (1,3,4/2,5-cyclohexanepentol), pinitol (3-O-methyl-chiro-inositol), 1-O-methyl-muco-inositol and muco-inositol have been identified for the first time in edible honeys by GC–MS of their O-trimethylsilyl derivatives, using their Kovats indices and mass spectral data. Individual cyclitol content (including myo-inositol for comparison) was estimated by using phenyl-β-glucoside as internal standard. Myo-inositol and pinitol were present in the 28 examined honey samples; quercitol, methyl-muco-inositol and muco-inositol were only detected in some samples. The presence, in honey, of these compounds could be used to distinguish among honey types, since they probably are collected by bees from wild plants.This work was financed by Programa Apı́cola Nacional (Project API99-0166), supported by the EU and Ministerio de Agricultura, Pesca y Alimentacion of Spain and by Programa Nacional de Alimentación (CAL01-066-C7-5), supported by Instituto Nacional de Investigación y Tecnologı́a Agraria y Alimentaria of Spain.Peer reviewe

Gas chromatographic-mass spectrometric method for the qualitative and quantitative determination of disaccharides and trisaccharides in honey

An improved method has been developed to identify and quantify honey disaccharides and trisaccharides by gas chromatography and mass spectrometry. The procedure, based on mass spectral and retention data (“retention time windows”) determined on two capillary columns with different stationary phases allowed the identification and quantitation in honey of 16 disaccharides and 9 trisaccharides, some of which were not previously identified by GC. The reliability of the analytical results was considerably improved by the use of this procedure: several unidentified disaccharides and trisaccharides were detected, and their presence was taken into account in the quantification.This work was financed by the Programa Apícola Nacional (Project API99-016) with the support of the EU and the Ministerio de Agricultura, Pesca y Alimentación (Spain), and by the Programa Nacional de Alimentación run by the Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (Project CAL01-066-C7-5).Peer reviewe

Volatile components in microwave- and conventionally-heated milk

Raw milk was microwave-heated in two different modes: at 120°C using closed vessels, and at 70–90°C using a continuous flow device. Conventional heatings were carried out at the same temperatures, using a glycerol bath or a water bath instead of the microwave oven. Samples were analyzed following a dynamic headspace method; the volatile components were quantified by GC and identified by GC–MS. Volatile composition was similar using both heating systems, although when milk was heated in closed vessels some quantitative differences were found between microwave and conventional heating. The latter results were attributed to the unevenness of microwave heating inside the vessels, whereas the continuous flow device seemed to allow a very uniform heating.This work was supported by the Comission of European Communities (Contract 1116/92 ESP 4-III) and Comunidad Autónoma de Madrid (Project COR-0025/94). E.V. acknowledges a grant from Comunidad Autónoma de Madrid.Peer reviewe