Isolation of volatiles

Fig. 5. Usual apparatus for the isolation of volatile and/or unstable compounds by evaporation or distillation in vacuo and condensation in a cooled receiver.

Maignial, L., Pibrot, P., Bonetti, G., Chaintrau, A., and Marion, J. P. (1992). Simultaneous distillation-extraction under static vacuum Isolation of volatile compounds at room temperature. J. Chromatogr. A 606, 87-94. 

Distillation is a suitable technique for the isolation of volatile organic compounds from liquid samples or the soluble portion of solid samples [24,27-30]. The physical basis of separation depends on the distribution of constituents between the liquid mixture and the vapor in equilibrium with that mixture. The more volatile constituents are concentrated in the vapor phase, which is collected after condensation. The effectiveness of the separation is dependent on the physical properties of the... 

Applications Simultaneous steam distillation-solvent extraction has been in use for many years [163]. Steam distillation combined with continuous liquid extraction is an efficient technique for the removal and isolation of volatile compounds in various matrices (environmental,... 

Many factors affect the volatile composition of fruit and vegetables, e.g. genetics, maturity, growing conditions and postharvest handling. Furthermore, preparation of the fruits and vegetables for consumption and the method for isolation of volatile compounds may change the volatile profile and key aroma compounds compared to non-processed fruits and vegetables. 

The compact distillation unit shown in Fig. 16.1 has been designed for the rapid and careful isolation of volatiles from the non-volatile food components [15]. This technique, denoted SAFE, is suitable for solvent extracts, aqueous samples, or matrices with high oil content. 

Table 16.1 Reactions leading to artefacts during isolation of volatiles ...

A contemporary of the method just described is the use of an absorbent (e.g. C-18) bonded onto granular or disk-type supports (solid-phase extraction [5]). The granular material is used in cartridge form (typically less than 5 ml), while disk forms are placed in a funnel/holder such as shown in Fig. 18.1b. A liquid (e.g. water, milk, or juice) would be passed through the cartridge (or filter disk), the analytes absorbed in the stationary matrix, the absorbent washed with water, and then the analytes of interest eluted from the absorbent with an organic solvent. This method has found limited use in the isolation of volatiles from foods but continues to find significant application in the analytical field overall [6]. 

Leahy, M.M. and Reineccius, G.A. 1984. Comparison of methods for the isolation of volatile compounds from aqueous model systems. In Anal. Volatiles Methods Appl., Proc. - Int. Workshop (P. Schreier, ed.) pp. 19-47. Walter de Gruyter, Berlin. 

Schultz, T.H., Flath, R.A., Mon, T.R., Eggling, S.B., andTeranishi, R. 1977. Isolation of volatile components from a model system. J. Agric. Food Chem. 25 446-449. 

Transfer the sample to an extraction apparatus or headspace adsorption device for the isolation of volatiles. 

It was also applied for the on-line isolation of volatile metals such as... 

Numerous reviews have appeared in the literature dealing with the isolation of volatile compounds from foods (1-6). Therefore, it appears of greater value to present some of the more recent developments in this area rather than repeat what is currently already reviewed. 

Isolation of Volatile Compounds from Oat Oil. Four oil samples were obtained from each oat variety, as shown in Figure 1. Each oil was isolated, in triplicate, for its volatile fraction by means of molecular vacuum distillation. The equipment used has been previously described (11, 12). Aliquots of 5.0 grams were used. The isolation was performed at room temperature and proceeded for 4 hours from the time secondary vacuum was... 

Figure 1. Isolation of volatile flavor compounds from the lipid fraction of dehulled oat seeds.

Isolation of Volatiles by Simultaneous Distillation/ Extraction. The dark brown reaction mixture was placed in a 4 1 round bottom flask and continuously extracted for seven hours with 200 ml pentane/diethy1 ether (1 1) at atmospheric pressure according to the procedure described by Likens/Nickerson. The pentane/ether extract... 

Borges, P., Pino, J. and Rosado, A. (1 990) The isolation of volatile oil from coriander fruit by steam distillation. Nahrung 34(9), 831-834. 

Fig. 25. The seven nuclear decay chains attributed to the decay of 269Hs leading to 265Sg, 26lRf and 257Lr or 270Hs leading to 266Sg and 262Rf registered in the COLD detector after chemical isolation of volatile tetroxides. Figure reproduced form [79].

The isolation of volatile flavor compounds from foods represents a major problem in einalytical studies of food flavor. Headspace methods are especially attractive since they are rapid, simple and measure what is typically presented to the nose. 

Isolation of Volatiles from Tomato Condensate. Condensate from commerical tomato paste production using vacuum concentration was stored at 5°C in the dark and used within a few days. 

Isolation of Volatiles for Quantitative Studies. The method used was essentually the same as that described previously (2). The whole tomato sample (lOOg at 25°C) of pieces cut from 3- different tomatoes was blended for 30 seconds (using a Waring blender with blades rotating at 13670 rev/min). The mixture was allowed to stand at room temperature for 180 seconds longer and... 

The reagent is suggested by W. Triebs for the isolation of volatile ketones from natural sources. Condensation with a ketone is conducted by refluxing with the reagent in aqueous alcohol buffered with sodium acetate. The reaction mixture is extracted with ether for removal of nonketonic material, the aqueous solution is treated with hydrochloric acid, and the ketone liberated is removed by steam distillation. 

Isolation of Volatiles. An aliquot of blended pulp (1.2 kg) was diluted with distilled water (700 mL) in a 3-L three-neck flask and vacuum distilled (25-30°C/l mm Hg). Distillation continued for 2.5 to 3 h yielding approximately 500 mL of distillate which was collected in two liquid nitrogen cooled traps. A total of 3.6 kg of fruit pulp was distilled in three batches. The distillates were combined and immediately frozen until use. The combined distillate was extracted in 250 mL batches for 20 h with 60 mL trichloro-fluoromethane (Freon 11, b p 23.8°C) using a continuous liquid-liquid extractor. The trichlorofluoromethane was distilled through a 120 x 1.3 cm glass distillation column, packed with Fenske helices, prior to use. Each extract was carefully concentrated to approximately 100 pL by distillation of solvent using a Vigreux column (16 cm), and a maximum pot temperature of 30°C. 

Isolation of volatile compounds by simultaneous steaia distillation-hexane extraction (SDE) Frozen burley tobacco stalks (1-4 kg) were cut perpendicular to the main axis into 0.5-cra sections and placed in a 12-L flask with 4 L of distilled water. The flask contents were steam distilled for 4 h in a continuous extraction apparatus of the type described by Likens and Nickerson... 

Isolation of volatile compounds by headspace trapping on Tenax A diagram of the glass-Teflon Tenax trap is shown in Figure 1. The... 

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