Headspace methods

Committee for Analytical Methods for Residue of Pesticides and Veterinarian Products in Foodstuffs by Headspace Method, of MAFF, Report by the Panel of the Determination of Dithiocar-bamate Residues, Ana/yit, 106,781 (1981). 

Headspace methods provide an indirect method of sample analysis suitable for the determination of organic volatiles [11,318-323]. The gas diase in contact with the sample and not the sample matrix itself is taken for analysis. If the sample is in thermodynamic equilibrium with the gas phase in a closed thermostated vessel, then this method of analysis is referred to as static headspace. If a carrier gas is passed over the sample and the sample volatiles accumulated in a cryogenic or sorbent trap, then the method is generally referred to as dynamic headspace. If the carrier gas is introduced below the surface of... 

Parameters influencing the performance of headspace methods include sample preparation, sample temperature, equilibration time, carrier gas pressure, pressurisa-tion time, sampling time and transfer line temperature. For validation of headspace instrumentation, see Kolb and Ettre [207],... 

SHS-GC is amongst the best methods of choice for volatile monomer analysis and effectively gives both isolation and preconcentration of the analyte in one step. Headspace methods are used extensively for... 

EPICS-static headspace method-GC/FID, Miller Stuart 2000)... 

Miller, M.E., Stuart, J.D. (2000) Measurement of aqueous Henry s law constants for oxygenates and aromatics found in gasolines by the static headspace method. Anal. Chem. 72, 622-625. 

Corwen [58] used this method for the analysis of ketones and aldehydes in seawater. Halocarbons were similarly separated from environmental samples by Kaiser and Oliver [59]. There have been many other applications of the technique [60-69]. The major advantage of the headspace method is simplicity in handling the materials. At most, only one chemical, the salt used in the salting-out procedure, needs to be added and in most cases the headspace gas can be injected directly into a gas chromatograph or carbon analyser. On the other hand the concentration of organic materials present is limited by the volume of seawater in the sample bottle. This is very much a batch process. 

In this method volatile organic matter in seawater is concentrated on a Tenax GC solid adsorbent trap and dry-ice trap in series. The trapped organic material is then desorbed and oxidised to carbon dioxide, which is measured with a non-dispersive infrared analyser. A dynamic headspace method was used for the extraction with the assistance of nitrogen purging. Dynamic headspace analysis [184] is an efficient extraction procedure. The efficiency of extraction... 

Vinyl chloride monomer (VCM) is the main substrate for the manufacture of polymers used as packaging materials for food. Since VCM is considered by lARC to be a human carcinogen, monomer levels in PVC food packaging materials are strictly controlled. To ensure a safe product, the residual content of VCM in the finished material or article is limited to one mg per kg in the final product (Council Directive 78/142/EEC). Furthermore, VCM should not be detectable in foodstuflfs. Commission Directives 80/766/EEC and 81/432/ EEC give the method of analysis for official control of the VCM level in food packaging materials and in foods - gas-phase chromatography using the headspace method, after dissolution or suspension of samples in N,N-dimethylacetamide. Both residual monomer content of the polymer and... 

Iliuta, M.C. and Larachi, F. Solubility of dimethyldisulfide (DMDS) in aqueons solntions of Fe(HI) complexes of trans-1,2-cyclohexanediaminetetraacetic acid (CDTA) using the static headspace method. Fluid Phase Equlllb., 233(2) 184-189,2005. 

Robbins, G., Wang, S., and Stuart, J.D. Using the static headspace method to determine Henry s law constants. Anal. Chem., 65(21) 3113-3118, 1993. 

The number of volatile compounds collected from white bread by the dynamic headspace method are presented per class in Table II. The values give only a partial impression, because they depend strongly on the conditions used for isolation and detection of volatile compounds. Overall this method seems to release 1/3 of the total number of compounds published for white bread (5). So, the data obtained can only be used for studying differences compared to control samples. 

Table II. Number of volatile compounds detected in white bread samples with the dynamic headspace method...

The analyses of the flavour composition of yellow passion fruits were performed by four dilferent isolation techniques, namely vacuum headspace sampling (VHS), the dynamic headspace method, simultaneous distillation and extraction at atmospheric pressure, and simultaneous distillation and extraction under reduced pressure [62]. Significant differences were found not only in the chemical composition of the resultant extracts but also in their sensory properties. The most representative and typical extract was obtained by VHS. 

The key advantage of this headspace method, compared to static headspace analysis, is the sensitivity obtained. While static headspace shows the status at equilibrium and can measure thermodynamic constants, purge-and-trap or dynamic headspace can measure the kinetics of... 

Werkoff, P., Giintert, M., Krammer, K Sommer, H., and Kaulen, J. 1998. Vacuum headspace method in aroma research Flavor chemistry of yellow passion fruits. J. Agric. Food Chem. 46 1076-1093. 

Stuart et al. [ 184] studied the analysis of volatile organic compounds in soil using an automated static headspace method. Recoveries increased in the or-... 

C, soil, sand and loess, sorption isotherm-headspace method, Grathwohl 1990)... 

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