Headspace trapping

When a comparative analysis of the headspace volatiles of living and picked osmanthus flowers was performed by the dynamic headspace trapping method using Tenax GC, even more dramatic differences were observed, shown in Table 20 (60). 

A number of different set-ups can be used. Figure G 1.2.2 shows one possible set-up of dynamic headspace trapping. Normally, the vessel contains the food product, an inlet for nitrogen gas, and an outlet connected to the trap. The inlet could be directed through the liquid food, often called purge-and-trap, or above the food, often called dynamic headspace sampling. 

Prepare dilute solution of sample in MeoH introduce into headspace trap... 

Volatile Compounds from Vegetative Tobacco and Wheat Obtained by Steam Distillation and Headspace Trapping... 

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

Figure 4. Dynamic headspace trapping of using Tenax traps...

Table 1 shows that the steam distillation-extraction of a large quantity of mushrooms yielded the most complete and complex sample for volatile analysis, when compared to the sorptive stirrer-bar and headspace trapping. The sorptive stirrer bar tends to extract fewer polar components and the headspace trapping is limited by volatility. A comparison of extraction techniques including supercritical fluid extraction as applied to Shiitake mushrooms is reported by Charpentier et al (18). 

In direct headspace analysis, the sample e g. serum or urine, is equilibrated with the headspace in a suitable container. A protion of headspace gas is then injected for analysis. More elaborate headspace trapping devices combine separation of the volatiles from the sample matrix with subsequent enrichment of the constituents. Such a system, suitable for small volumes of body fluids, is known as the transevaporator sampling technique. It contains a microcolumn packed with Porasil E (pore silica gel), into which the sample is injected. In one mode of use, helium is passed through the column to remove the volatiles which are then collected in a trap (Tenax-GC, a porous polymer, 2,6-diphenyl-p-phenylene oxide). 

Identified by Merritt and Robertson (1966) in their coffee aroma (see Section 5.B), by Ho etal. (1993) in the volatile compounds of a roasted Colombian coffee (headspace trapping with short-path thermal desorption GC/MS), the concentration given is 0.1 ppm. 

Shimoda M., Wada K. and Osajima Y. (1984b) Aroma of coffee VI. Effect of temperature of headspace trapping apparatus on quantification of coffee volatiles. Nippon Shokuhin Kogyo Gakkaishi (J. Jpn. Soc. Food Sci. Technol) 31, 805-9. (Chem. Abstr. 102, 147641). 

Most essential oils are complex mixtures involving from a few to several hundred compounds. The techniques for collecting floral fragrances and other similar mixtures of essential oils have been reviewed (Charlwood and Chari-wood, 1991a Gershenzon and Croteau, 1990, 1991 Hills and Schutzman, 1990). Extraction with supercritical liquids and headspace trapping are useful to avoid decomposition of essential oil components. 

Grecsek, H. Analysis of fuel oxygenates by US EPA Method 8260B using headspace trap with GC/MS. http //las.perkinelmer.com/content/ApplicationNotes/fueloxygenateshstrap-gcmslar. pdf, 2005. 

Hildebrand, Volatile compounds from vegetative tobacco and other plants obtained by steam distillation and headspace trapping, la. "Biogenesis of aroma," T. H. Parliment and R. Croteau, eds., American Chemical Society Symposium Series, No. 317, ACS, Washington, D.C. (in press). 

JS Elmore, DS Mottram. Extraction of novel thiazoles and 3-thiazolines from cooked beef by headspace trapping onto Tenax. In CJ Mussinan, MJ Morello,... 

Figure 7 Typical solvent desorption headspace trap, (a) Glass capillaries (b) glass wool (c) Porpak Q (d) microliter syringe (e) ampoule.

The Zenith trap constructed from GC capillary tubes obtained from Supelco (26) was directly compared to conventional dynamic headspace with a Tenax trap by simultaneous collection of the scent of a blue hyacinth flower. The resulls obtained from the bundled capillaries are compared to the Tenax headspace trapping system in Table 2. It was concluded that the Zenith trap is comparable to... 

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