Headspace analysis dynamic methods

Direct methods of analysis such as distillation [158,167,168], liquid-liquid extraction [ 159,169], headspace analysis [ 170-172], dynamic headspace analysis [157,173-178], and direct injection [179] have been used mainly for specific volatile components. 

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... 

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... 

Theirry, A., Maillard, M. B., and Le Quere, J. L. (1999). Dynamic headspace analysis of Emmental aqueous phase as a method to quantify changes in volatile flavor compounds during ripening. Int. Dairy. 9, 453-463. 

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). 

Soil spiked with trichloroethylene and toluene was analysed using a gas chromatograph equipped with a PT concentrator that was found to be replaceable by a headspace unit in order to simplify the overall assembly. The headspace analysis of soil samples was found to be restricted by incomplete desorption of the contaminants in soil-water mixtures this shortcoming, however, was effectively overcome by the addition of methanol. Henry s law constants for volatile organics in methanol must previously be determined if the method is to be applied to soils [142]. A comparison of the performance of static and dynamic (PT) headspace modes in the determination of nine VOCs in five different soils revealed poor PT recoveries in relation to those of static headspace (which ranged from 68 to 88%) the latter, however, required longer development times [143],... 

A dynamic headspace gas-partitioning method has been used to assess the effect of dissolved organic carbon on the value of H for mirex (Yin and Hassett 1986), and with a gas chromatographic detection system for analysis, this is applicable to native water samples containing mirex. 

Fig.l Headspace analysis and microextraction methods (here only the headspace mode is shown) used for the determination of fuel oxygenates, (a) Headspace analysis, (b) headspace solid-phase microextraction (HS-SPME) redrawn after [60], (c) solid-phase dynamic extraction (SPDE) redrawn after [61] and (d) liquid-phase microextraction (LPME) redrawn after [62]... 

Wasik and Brown (34) later modified McAuliffes static headspace method. They constructed a dynamic headspace analysis unit where... 

Various gas chromatographic (GC) methods, such as direct injection, dynamic headspace, and static headspace, have been used for the analysis of volatile products, resulting from the oxidative deterioration of vegetable oils. Though advantages and disadvantages are apparent with each GC method, for routine analyses, static headspace is the method of choice because it is rapid and requires no cleaning between samples. ... 

Table 3.2 Headspace analysis of oxidized soya bean oil (peroxide value 9.5) by three methods direct injection, dynamic headspace gas chromatography (HSGC) and static HSGC. OlOOH = oleic acid hydroperoxide LoOOH = linoleic acid hydroperoxide LnOOH = linolenic acid hydroperoxide.

Hagman and co-workers [3] and Schmidt and co-workers [4] used dynamic headspace analysis to study volatiles in polypropylene-polyethylene copolymers and PVC and polyethylene terephthalate. In the latter method [3], volatiles from PET and PVC were collected and separated by open tubular GC. Other solid polymer headspace methods discussed include hexane, tridicane and butylated hydroxytoluene in polypropylene [5], vinyl chloride, vinyl acetate, acetaldehyde and water in vinyl and acrylic polymers and polyolefins [6], ethyl acetate and toluene in laminated polyolefins [7], miscellaneous volatiles in polymers [8] and solvents retained in plastic films [9-12]. 

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

Trace component analysis will require some method of headspace concentration (dynamic headspace analysis), which permits sampling of large volumes of headspace (100-1000 L) thereby compensating for low headspace concentrations. 

Westendorf, R.G. (1985) A quantitation method for dynamic headspace analysis using multiple runs. J. Chromatogr. ScL,... 

Various methods have been used to investigate oral malodors including direct oral sampling for volatile sulfur materials and dynamic headspace analysis of incubated saliva. These approaches have been used in clinical evaluation of materials to ameliorate oral malodors as well as identifying all materials that contribute to the malodor or are indicators of oral disease (23-27). SPME analysis has been used to sample human breath (28). In this study, systemic air from diabetics was analyzed for ethanol, acetone, and isoprene. 

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). 

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... 

Small solid seuaples can be analyzed directly by dynamic headspace sampling using a platinum coil and quartz crucible pyrolyzer and cold trap coupled to an open tubular column (341,369,379). This method has been used primarily for the analysis of mineral samples and of additives, catalysts and byproducts in finished polymers which yield unreliable results using conventional headspace techniques owing to the slow release of the volatiles to the headspace. At the higher temperatures (450-1000 C) available with the pyrolyzer the volatiles are more readily and completely removed from the sample providing for quantitative analysis. 

Applications The potential of a variety of direct solid sampling methods for in-polymer additive analysis by GC has been reviewed and critically evaluated, in particular, static and dynamic headspace, solid-phase microextraction and thermal desorption [33]. It has been reported that many more products were identified after SPME-GC-MS than after DHS-GC-MS [35], Off-line use of an amino SPE cartridge for sample cleanup and enrichment, followed by TLC, has allowed detection of 11 synthetic colours in beverage products at sub-ppm level [36], SFE-TLC was also used for the analysis of a vitamin oil mixture [16]. 

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). 

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