Headspace sampling techniques

Prom the experimental point of view the static headspace sampling technique is very simple. The sample, either solid or liquid, is placed in a glass vial of appropriate size and closed with a Teflon-lined silicone septum. The 1 is carefully... 

Bicchi, C., Cordero, C. and Rubiolo, P. (2004) A survey on high-concentration-capability headspace sampling techniques in the analysis of flavors and fragrances. J. Chromatogr. Sci. 42, 402-409. 

Headspace Sampling Technique. The method used a new gas chromatographic desorption - concentration - GC introduction device (D.C.I.) based on dynamic headspace analysis and available from Delsi Instruments (Paris, France). This apparatus made it possible to isolate volatiles from both solid and liquid samples (4). 

A substantial amount of information on volatiles can be obtained with less than 30 g of each of these samples in a direct DHS/GC/MS analysis. DHS operation sweeps volatile flavors from the surface of food samples in a similar way as we sniff for the volatile flavors of a food. DHS does not require high sampling temperature or solvent for extraction and may be considered as a lcw-artifact arcma sampling technique. The concentrating effect of DHS provides better sensitivity than static headspace sampling. Techniques such as GC-coupled aroma perception and GC/MS identification can be used to complement other approaches in improvement of flavor quality of a variety of products. 

The headspace sampling technique developed in the present study to collect volatiles from cold stored Black Truffles performed adequately. Indeed, the aroma Isolate obtained was described as typical, and 11 minor compounds could be described for the first time as Black Truffle aroma constituents. Moreover, these results allowed the formulation of the first Nature-Identical Black Truffle aromatizer. 

The headspace sampling technique can yield useful results if sufficient numbers of samples can be collected to use statistical populations to suggest anomalous areas. One should always exercise caution, however, with respect to characterisation of gas composition, since evaporation during the collection stage always occurs, resulting in the relative depletion of the lighter gases. 

Before analysis, the bacterial cultures should be transferred into standard 20 ml headspace vials and sealed with PTFE-lined Teflon caps to equilibrate the headspace. Sample handling is a critical step affecting the analysis by E-nose. The quality of the analysis can be improved by adopting an appropriate sampling technique. To introduce the volatile compounds present in the headspace (HS) of the sample into the E-nose s detection system, several headspace sampling techniques have been used in E-nose. Typically, the methods of headspace sampling (Ayoko, 2004) include static headspace (SHS) technique, purge and trap (P T) technique, stir bar sorptive extraction (SBSE) technique, inside-needle dynamic... 

The different headspace sampling techniques can be classified into one-step procedures, such as static headspace, where an aliquot of the vapor phase is transferred in a closed container directly to the gas chromatograph, and two-step procedures, where the volatile analytes are transferred from the matrix of the headspace to a "trap" where they are released... 

Bicchi, C. Cordero, P. Rubiolo, P. (2004). A Survey on High-Concentration Capability Headspace Sampling Techniques in the Analysis of Flavors and Fragrances. /. Chromatogr. Sci., Vol.42, pp. 402-409, ISSN 00219665. 

Monomeric residues in polymeric formulations or products can be determined using headspace techniques. Thus, monomeric impurities in aqueous suspensions of polymers for subsequent processing can be determined as a means of reducing possible off-odors in the processed materials. In commercial polymers, monomeric species can be identified and quantified using headspace sampling techniques with the appropriate analytical method. Such monomers may be undesirable with respect to subsequent usage, especially as packaging for food that may then become tainted by the volatile species present. 

In a small number of selected examples it is possible to use headspace sampling techniques as part of an analytical procedure to determine involatile components in a sample. The headspace sampling usually follows a chemical treatment to produce a volatile compound from the analyte of interest. It is thus possible to determine fluoride in fluorinated milk following initial treatment to produce volatile trifluorosilane. 

The coupling of a pervaporator to a gas chromatograph is one of the most promising uses of pervaporation and is worth a more detailed discussion, because of the advantages that pervaporation presents as compared with both static and dynamic headspace sampling techniques. In the static approach, the sample is placed in a closed chamber and heated until the volatile compoimds in the headspace reach the equilibrium with the sample. Then, part of... 

Callus cultures were established with three olive (Olea europaea L.) varieties using a method reported previously (2). Volatiles were collected from the olive cultures (20g) using dynamic headspace sampling techniques described previously (3). Analysis of volatiles was performed using an Automatic Thermal Desorption System linked to a Perkin Elmer Autosystem GC. Lipoxygenase (LOX) activity of the cultures was assayed routinely using an oxygen electrode. 

VOC analysis by headspace sampling technique Purge-and-trap sampling technique... 

Heat extraction techniques for solid sample preparation in GC are static and dynamic headspace analysis (SHS, DHS, HS-SPME and HSSE), thermal desorption (TD-GC, TD-GC-MS), pyrolysis and thermochromatography. Nomenclature is not unambiguous as to DHS, TD and PT. The terminology purge-and-trap is usually preferred for the simplest dynamic technique in which it is not necessary to subject the sample to either solvents or elevated temperatures. Scheme 2.7 shows the family of headspace sampling techniques. Headspace sorptive extraction (HSSE) and HS-SPME represent high capacity static headspace. 

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