Sustancias volátiles implicadas en las fermentaciones alcohólica y acética

Tesis doctoral inédita leída en la Universidad Autónoma de Madrid, Facultad de Ciencias, Departamento de Química. Fecha de Lectura: 01-01-198

Direct headspace sampling with on-column thermal focusing in capillary gas chromatography

A simple and inexpensive home-made device for thermally focusing the chromatographic band in a short length of the capillary column itself is described. The system allows one to optimize the direction and the effect of the thermal gradients established during the cryofocusing and thermal focusing and also provides an effective and rapid desorption of the sample. As a result, a simultaneous double thermal focusing effect, which improves the chromatographic resolution of the less retained solutes, is achieved. Examples of headspace analysis performed with the proposed device are included.Peer reviewe

Evaluation of a PTV injector for quantitative analysis of volatile compounds at low concentrations

The performance of a PTV injector operated in the solvent venting mode with Tenax in the glass insert was evaluated with synthetic mixtures containing 5 to 50 ng of n-alkanes, ethyl esters, n-alcohols, and carboxylic acids. The influence of the sampled amount, the injected volume, and the nature of the solvent on accuracy and precision were studied. Coefficients of variation of relative (normalized) peak areas and absolute peak area ratios of each compound to the standard are of the order of 5 %.Peer reviewe

Gas chromatographic analysis of free carboxylic acids in foods using a micropacked column

A micropacked column packed with FFAP 4% on desilanized Volaspher A-2 is proposed for determining free carboxylic acids (C2–C20, and C16:1, C18:1, C18:2, C18:3, i-C4 and i-C5) without derivatization. The column has high efficiency and separates several carboxylic acids in extracts of food samples without a separate acid extraction. For very complex real mixtures, an additional extraction provides an excellent acid profile. Thermal degradation was not observed for unsaturated acids and the accuracy and precision of the analysis were good.This work was made possible by financial assistance from the Commission Asesora de Investigacion Cientifica y Tecnica, Project 237/84. T.H. is grateful to the Ministerio de Educacion y Ciencia for a grant.Peer reviewe

Comparison of the performances of hot and cold sample introduction with a programmed-temperature vaporizer in the split and splitless modes

The performances of hot and cold sample introduction with a programmed-temperature vaporizer operated in the split and splitless modes were compared. Synthetic mixtures of n-alkanes, ethyl esters, n-alkanols and carboxylic acids were tested using both Tenax GC or Volaspher A-2 as packing materials. Cold temperature-programmed injection in the splitless mode with Tenax as the packing material provided good accuracy and precision for quantitative measurements.This work was made possible by financial assistance from the Comision Asesora de Investigation Cientifica y Tecnica, Proyect 237/84. T.H. and E.L. are grateful to the Ministerio de Educacion y Ciencia and the Instituto de Cooperation Iberoamericana, respectively, for grants.Peer reviewe

Capillary gas chromatographic determination of volatiles in solid matrices by direct introduction using a programmable-temperature vaporizer

A simple method for the rapid and reliable analysis of solid matrices by direct introduction in the glass liner of a programmed-temperature vaporizer is proposed. The procedure requires only very small sizes (about 0.1 mg), does not require pretreatment or concentration steps and can be carried out in less than 40 min. A comparison between composition data obtaned from Rosmarinus officinalis leaves analysis by both simultaneous distillation extraction and direct introduction of the plant in the programmed-temperature vaporizer is also included. The proposed procedure allows the reproducible determination of the volatile composition of a plant with coefficients of variation of less than 5%.This work was made possible by financial assistance from the Comision Interministerial de Ciencia y Tecnologia, Proyect ALI-88-0237. One of the authors (T.H.) thanks the Ministerio de Education y Ciencia for a grant.Peer reviewe

Use of micropacked columns for quantitative SFC

The performance of a type of micropacked column for the quantitative SFC analysis of samples containing solutes at very different concentrations has been studied. The chromatographic characteristics of the column were compatible with high sample volume loadability, and at the same time adequate efficiency and low pressure drop. In order to increase both the separating power and sample capacity of the column, the percentage liquid phase loading was optimized. The accuracy, precision, and detection limit obtainable with the micropacked column are compared with the performance of a wall coated open tubular capillary column having the same phase ratio.Peer reviewe

On-line SFE-SFC coupling using micropacked columns

Short Communication.Peer reviewe

Stereodifferentiation of some chiral aroma compounds in wine using solid phase microextraction and multidimensional gas chromatography

The stereodifferentiation of some chiral components of importance for the character or intensity of wine aroma was achieved with headspace solid phase microextraction and multidimensional gas chromatography coupled to mass spectrometry. Chiral evaluation of linalool and 2,3-butanediol is performed in less than 75. min (overall analysis time) using a polydimethylsiloxane/divinylbenzene fibre during the sample concentration step and permethylated β-cyclodextrin as the chiral stationary phase in the main column of the multidimensional system. Enantiomeric excesses of linalool and percentage values of 2,3-butanediol stereoisomers were determined in three different white wines. © 2010 Elsevier Ltd.Peer Reviewe

Sensory profile of wines. Quality index

Peer reviewe