Headspace analyzers static

Schoenmakers et al. [72] analyzed two representative commercial rubbers by gas chromatography-mass spectrometry (GC-MS) and detected more than 100 different compounds. The rubbers, mixtures of isobutylene and isoprene, were analyzed after being cryogenically grinded and submitted to two different extraction procedures a Sohxlet extraction with a series of solvents and a static-headspace extraction, which entailed placing the sample in a 20-mL sealed vial in an oven at 110°C for 5,20, or 50 min. Although these are not the conditions to which pharmaceutical products are submitted, the results may give an idea of which compounds could be expected from these materials. Residual monomers, isobutylene in the dimeric or tetrameric form, and compounds derived from the scission of the polymeric chain were found in the extracts. Table 32 presents an overview of the nature of the compounds identified in the headspace and Soxhlet extracts of the polymers. While the liquid-phase extraction was able to extract less volatile compounds, the headspace technique was able to show the presence of compounds with low molecular mass... 

Static headspace GC involves heating the sample in an air-tight environment until the volatile lipids in the food reach an equilibrium with those in the surrounding air. The air above the sample (headspace) is then sampled and analyzed. Flame ionization detection (GC-FID) can be used for quantification and mass-selective detection (GC-MS) can be used for compound identification. This protocol also outlines semiquantitative and quantitative approaches for determination of volatile lipid concentration, and is particularly designed for analysis of a meat sample. 

In flavor analysis, the most frequent use of volatile traps is in analyzing the flavor compounds in foods using purge-and-trap or dynamic headspace, followed by GC-MS or GCO. Additionally, the traps can be used to measure static headspace and air-matrix partition coefficients where air is pushed out of an equilibrated cell containing the sample onto a volatile trap (Chaintreau et al., 1995). Volatile traps have been also used for flavor release measurements during eating (Linforth and Taylor, 1993) or simulated eating (Roberts and Acree, 1995). 

The ease of initial sample preparation is one of the clear advantages of static headspace extraction. Often, for qualitative analysis, the sample can be placed directly into the headspace vial and analyzed with no additional... 

Quadrapole mass analyzers are by far the most common type of mass spectrometer in use today and the literature on these type of analyzers is extensive. Quadrapole mass analyzers are often thought of as mass filters because they can be tuned to transmit ions of a narrow range of mass/charge (w/z) ratios. Fig. 6 shows a generalized block schematic of a quadrapole mass spectrometer. A typical quadrapole instrument separates ions with different masses by application of a combination of static and radio frequency electric fields to four cylindrical rods. A headspace gas sample is introduced at an inlet and fed into an ion source where electrons are emitted from a filament and ionize the sample gas. The sample ions are then accelerated in an electrical field and are injected into the opening at the center of the rods. In the simplest systems, one pair of rods is connected and attached to the positive... 

Ereeze-dried MlOO and M180 samples were rehumidified by storing them for at least 1 week in vacuum desiccators at relative humidities of 66 and 54%, respectively, at 25°C. The rehumidified samples were stored at 45, 50, and 60°C in order to study the release of aroma compoimds as a function of storage time. The release of benzaldehyde and ethyl acetate was analyzed using static headspace gas chromatography (EB 40 XC, Perkin Elmer, USA) and an electronic nose (Gas Detector MGD-1, Environics Ltd, Finland). 

Gas chromatographic (GC) methods have been used for determining volatile oxidation products. Static headspace, dynamic headspace or direct injection methods are the three commonly used approaches. These methods were compared in an analysis of volatile compounds in an oxidized soybean oil. It was found that each method produced significantly different GC profiles (Frankel 1985). The dynamic headspace and direct injection methods gave similar results, but the static headspace is more sensitive to low molecular weight compounds. Lee and co-workers (1995) developed a dynamic headspace procedure for isolating and analyzing the volatiles from oxidized soybean oil, and equations were derived from theoretical considerations that allowed the actual concentration of each flavor component to be calculated. 

Eight different lime and lemon flavor formulations were provided by a commercial flavor company (Table I). Six replicas of each flavor were analyzed using 7.5 uL aliquots. The aliquots were placed in 10 mL vials which were crimped and equilibrated for 15 minutes at 60 °C before static headspace sampling. The headspace parameters were 15 min incubation, 65 °C syringe, 0.75 min flushing of syringe after injection, cycle time of 4 min. Two mL were filled and injected at a 250 uL/s. There is no column for a separation prior to the mass selective detector (MSD), the entire headspace of each sample is introduced into the MSD. 

It should be stressed that the use of a general pharmacopeial method is not a reason not to validate the latter when analyzing a particular substance. The matrix effect, in particular, has to be investigated when using the static headspace mode of injection. 

If the components of interest in a solid or liquid sample are volatile, a good way to analyze them is to examine the concentration of these analytes in the gas phase above the matrix (headspace) when in a closed container, either by taking a sample directly from the gas phase or trapping and concentrating the gas prior to analysis. This type of extraction techniques are known as headspace analysis (Smith, 2003) the analysis and subsequent separation of volatile substances is normally carried out by the technique of gas chromatography, which is a mature technology, reliable and supported by a large body of work. The sample can be in contact and in equilibrium with the extractant gas (static or equilibrium headspace), or volatile compormds can be extracted by a steady stream of inert gas (dynamic headspace). 

The four most common approaches to quantitative static headspace gas chromatography calibration are external standard, internal standard, standard addition and multiple headspace extraction (MHE). The choice of technique depends on the type of sample being analyzed (Slack et al, 2003). 

Static headspace gas chromatography is a mature and reliable technique it is considered the technique of choice for the analysis of ethanol in biological samples, and is therefore jrresent in the vast majority of forensic laboratories around the world with the qualified personnel to operate it however, the applicability of this technique is not limited to this test and can be used for the analysis of various substances with minimal modifications, providing proper calibration and proper handling of matrix effects, excellent validation parameters, along with a clean injection. So, with this technique, various substances can be analyzed without the need of additional methods, and that would allow forensic laboratories to expand the number of cases they can take care of, with a minimal investment. 

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