Pyrolysis headspace

Liquid (solvent) extraction is not the only way of sample preparation, but stands along with various forms of heat extraction (headspace, thermal desorption, pyrolysis, etc.) and with laser desorption techniques. 

Diffusive sampler Membrane extraction (MESI) Liquid-liquid extraction (LLE) Solid-phase extraction (SPE) SPE-PTV-GC Solid-phase microextraction (SPME) Headspace GC (SHS, DHS) Large-volume injection (LVI) Coupled HPLC-GC Membrane extraction (MESI) Difficult matrix introduction (DMI) Conventional solvent extraction methods 1 Pressurised solvent extraction methods Headspace GC (SHS, DHS) Thermal desorption (TD, DTD) Pyrolysis (Py) Photolysis Photon extraction (LD) Difficult matrix introduction (DMI)... 

Various ancillary GC techniques are headspace GC (Section 4.2.2), thermal desorption GC, pyrolysis GC, hyphenated methods (Chapter 7), multidimensional techniques (Section 7.4.1) and process GC. 

The most common precolumn chromatographic techniques discussed here are SFE (Section 3.4.2), SPE (Section 3.5.1) and SPME (Section 3.5.2). However, sampling methods such as thermal desorption, pyrolysis and headspace (Section 4.2.2) may also be classified in this category. 

The method allowed the authors to characterise a pine pitch (viscous tar derived from the distillation of wood of pine trees). The main constituents detected by headspace SPME result from the pyrolysis of the lignin, guaiacol (11) and its p-w-alkyl derivatives [methyl... 

Implementation The GC-MS of the sample headspace finds no perfume compounds. The cream is found to be greater than 80-wt% organic matter. Pyrolysis-GC-MS identified significant levels of glucose polymers, which were confirmed by FTIR to be either cellulose or starch. The iodine test revealed that the glucose polymer was starch. Further GC-MS analysis did not find cholesterol, but did find trace levels of a cholesterol degradation product. 

EXMAT - A Linked Network of Expert Systems for Materials Analysis. Seven individual expert systems comprise EXMAT (1) problem definition and analytical strategy (2) instrumental configuration and conditions (3) data generation (4) chemometric/search algorithms (5) results (6) interpretation (7) analytical goals. Dynamic headspace (DHS)/GC and pyrolysis GC (PGC)/concentrators... 

Inks and prints are analysed in order to ensure safety. This includes testing for harmful substances with potential to migrate into food. Environmental pressure may result in a demand for testing, for example, vegetable oils versus petroleum distillates. There might also be a need to determine the content of aromatic compounds in the ink in order to avoid odour and taint problems. For chemical analysis of prints and determination of ink components a number of methods are available, such as pyrolysis, infra-red spectrometry, gas chromatography and mass spectrometry. Volatile compounds are usually analysed by a headspace technique. The progress in chemical analysis is so rapid that any method may be considered obsolete after a limited number of... 

The combination of a SPME device with a pyrolysis gas chromatographic (GC) IMS system improved the limit of detection of tributylphosphate (TBP, which served as a simulant) in water by a factor of 20 compared to the same system without the SPME device. SPME fibers were also used to sample headspace vapors of several types of nerve agents, and the fibers were introduced directly into a modified ESI source for subsequent detection by IMS and mass spectrometry (MS). A SPME-IMS system, with thermal desorption, was also used to screen soil samples for precursor and degradation products of CWAs, and it was found that fibers of polydimethyl-siloxane (PDMS) were superior to PDMS-divinylbenzene fibers. ... 

Paper (which is primarily cellulose), printing ink, writing ink, and photocopy toners have all been analyzed by pyrolysis, sometimes independently as pure materials and sometimes intact as a fragment of a document. Zimmerman et al. used pyrolysis-GC to extend the specificity of toner identification in photocopies. Ballpoint pen ink, various papers, and photocopy toners have been analyzed using a combination of headspace sampling and pyrolysis by Wampler and Levy. ... 

See also Activation Analysis Neutron Activation. Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Chromatography Overview Principles. Gas Chromatography Pyrolysis Mass Spectrometry. Headspace Analysis Static Purge and Trap. Infrared Spectroscopy Near-Infrared Industrial Applications. Liquid Chromatography Normal Phase Reversed Phase Size-Exclusion. Microscopy Techniques Scanning Electron Microscopy. Polymers Natural Rubber Synthetic. Process Analysis Chromatography. Sample Dissolution for Elemental Analysis Dry... 

While liquid-liquid, headspace, and sorbent-based extractions are perhaps the most commonly nsed and pnbhshed sample preparation techniqnes for GC, there are numerous additional techniques to consider. While we do not attempt to fully describe every technique that has ever been nsed, the techniques described below are certainly of importance in the arsenal of sample preparation techniques for GC. These include supercritical-fluid extraction, accelerated solvent extraction, microwave-assisted extraction, pyrolysis, thermal desorption, and membrane-based extractions, pins comments on antomation and derivatization. 

As mentioned previously, the most common container for fire debris is an unused metal paint can. Normally a hole is punched in the lid of the can and sealed with tape before the can is sampled. Samples are typically heated in an oven or on a hot plate for 10-30 min at temperatures of 50-90°C. If enough accelerant is present to cause an odor, the analyst may elect to sample the container at room temperature. Heating samples that contain water above 90° C may cause the container to vent or burst. In addition, over heating the sample may cause pyrolysis of debris and complicate the interpretation of an already complex chromatogram. Typically, 0.5-3 mL of headspace vapor is removed from the... 

The first preliminary work in which vapor examination of headspace samples was used for the analysis of traces of accelerants was reported by Midkiff and Washington in 1972 (180). Since then many studies have been performed in regard to heating conditions, container size, sample size, the effect of water, the degree of interference from pyrolysis products, and the chromatographic conditions, including the type and dimension of column. 

Thermal evolution analysis is an excellent tool for polymer studies complementary to other thermal techniques such as DTA, TG and pyrolysis. Its applications include thermal degradation studies, determination of additives and contaminants, polymer composition and structure identifications. With small variations, the apparatus can also be used for vapour pressure measurements, and for determination of odorous materials in polymer systems. Coupling of TEA to GC for the identification of effluents is practicable and useful. TEA-CT-GC was used for the analysis of volatiles from ABS 10 ppb of styrene but negligible acrylonitrile was detected in the headspace of a typical ABS resin [42]. 

Chances for successful identification and quantification are considerably enhanced when analytes are separated. For solutions, chromatography is the supreme tool, whereas for solids some form of thermal treatment may achieve fractionation of matter according to volatility. Vapour evolution from polymers may be controlled and studied by various means, such as sublimation, thermal distillation, vacuum TG-MS, thermal evolution analysis (TEA) including TVA, headspace techniques or thermal desorption. It is obviously desirable that evaporation of the additives takes place below the decomposition temperature of the polymer. In principle, this can also be realised in thermal-programmed pyrolysis (dry distillation in vacuum). Desorption processes are controlled by diffusion. 

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. 

Sharma N, Jain A, Verma KK (2011) Headspace solid-phase microextraction and on-fibre derivatization of primary aromatic amines for their determination by pyrolysis to aryl isothiocyanates and gas chromatography-mass spectrometry. Anal Methods 3(4) 970-976. doi 10.1039/C0AY00745E... 

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