Extraction dynamic headspace

Bianchi, F., Careri, M., and Musci, M. (2005). Volatile norisoprenoids as markers of botanical origin of Sardinian strawberry-tree (Arbutus unedo L.) honey Characterisation of aroma compounds by dynamic headspace extraction and gas chromatography-mass spectrometry. Food Chem. 89,527-532. 

Some methods are available for determining -hexane in urine and tissues. A modified dynamic headspace extraction method for urine, mother s milk, and adipose tissue has been reported (Michael et al. 1980). Volatiles swept from the sample are analyzed by capillary GC/FID. Acceptable recovery was reported for model compounds detection limits were not reported (Michael et al. 1980). A solvent extraction procedure utilizing isotope dilution followed by GC/MS analysis has been reported for tissues (White et al. 1979). Recovery was good (104%) and detection limits are approximately 100 ng/mL (White etal. 1979). 

Dynamic headspace-extraction stripping and purge-and-trap methodology are used most often for determination of M-hcxanc in water and hazardous wastes. Dynamic headspace extraction techniques have been applied to water samples (Roberts and Burton 1994) and sediment (Bianchi et al. 1991). Detection limits of 0.5 g/L were reported for lake water (Roberts and Burton 1994) and 20 ng/kg (ppt) for sediment (Bianchi et al. 1991). Supercritical fluid extraction (SFE) is a relatively new technique that has been applied to -hcxane in soil (Yang et al. 1995). Membrane extraction of M-hexane from water samples has been developed to provide online, continuous monitoring (Wong et al. 1995 Xu and Mitra... 

A first approach to analyze such volatiles is the application of the AEDA on extracts prepared by dynamic headspace extraction. An apparatus used for the extraction especially of solid foods is shown in Figure 5 [55]. The powdered material is placed into a rotating cylinder and the volatiles are continuously flushed onto a polymer material (Tenax( )) by using a stream of helium (1 L/min). After 3 hr the volatiles are desorbed from the polymer by elution with a small amount of diethyl ether and evaluated by AEDA after concentration. Since different yields may change the composition of the volatiles during headspace extraction [7], it is essential to sensorially evaluate the flavor of the extracts in comparison with the food flavor itself. The following examples show applications of this method on fresh and stored wheat bread crust [55] and on fresh rye bread crust [P. Schieberle and W. Grosch, unpublished results]. 

Figure 5. Apparatus used for the dynamic headspace extraction of solid foods. (1) Carrier gas (He) inlet, (2) belt transmission, (3) glass cylinder (99 x 8.5 cm), (4) Tenax trap (16 x 1.8 cm), (5) thermostat [adapted from reference 55],...

For the analysis of trace quantities of analytes, or where an exhaustive extraction of the analytes is required, purge and trap, or dynamic headspace extraction, is preferred over static headspace extraction. Like static head-space sampling, purge and trap relies on the volatility of the analytes to achieve extraction from the matrix. However, the volatile analytes do not equilibrate between the gas phase and matrix. Instead, they are removed from the sample continuously by a flowing gas. This provides a concentration gradient, which aids in the exhaustive extraction of the analytes. 

In dynamic headspace extraction (purge and trap extraction mode), the constant passage of carrier gas through a warmed sample (purge), followed by trapping of the purged volatiles on a sorbent (trap) and desorption into a gas chromatograph take place. 

WENZL T and lankmayr e p (2002), Comparative studies of the static and dynamic headspace extraction of saturated short chain aldehydes from ceUulose-based packaging materials , Anal Bioanal Chem, ill, 649-653. 

Although a dynamic headspace extraction (HS) method was often applied for the analysis of yogurt flavor (Imhof and Bosset, 1994), simultaneous distillation extraction... 

In-tube extraction, automated dynamic headspace extraction technique using a packed syringe needle, injection by thermal desorption in a GC injector. 

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