Spectrometry, thermal desorption

Desorption ionization (DI). General term to encompass the various procedures (e.g., secondary ion mass spectrometry, fast-atom bombardment, californium fission fragment desorption, thermal desorption) in which ions are generated directly from a solid or liquid sample by energy input. Experimental conditions must be clearly stated. 

This article discusses why one would choose nonresonant multiphoton ionization for mass spectrometry of solid surfaces. Examples are given for depth profiling by this method along with thermal desorption studies. 

Diethyl sulphate and dimethyl sulphate Lab method using Tenax sorbent tube, thermal desorption and gas chromatography with mass spectrometry 89... 

We have undertaken a series of experiments Involving thin film models of such powdered transition metal catalysts (13,14). In this paper we present a brief review of the results we have obtained to date Involving platinum and rhodium deposited on thin films of tltanla, the latter prepared by oxidation of a tltanliua single crystal. These systems are prepared and characterized under well-controlled conditions. We have used thermal desorption spectroscopy (TDS), Auger electron spectroscopy (AES) and static secondary Ion mass spectrometry (SSIMS). Our results Illustrate the power of SSIMS In understanding the processes that take place during thermal treatment of these thin films. Thermal desorption spectroscopy Is used to characterize the adsorption and desorption of small molecules, In particular, carbon monoxide. AES confirms the SSIMS results and was used to verify the surface cleanliness of the films as they were prepared. 

Thermal desorption spectroscopy and temperature programmed reaction experiments have provided significant insight into the chemistry of a wide variety of reactions on well characterized surfaces. In such experiments, characterized, adsorbate covered, surfaces are heated at rates of 10-100 K/sec and molecular species which desorb are monitored by mass spectrometry. Typically, several masses are monitored in each experiment by computer multiplexing techniques. Often, in such experiments, the species desorbed are the result of a surface reaction during the temperature ramp. 

In a study on the identification of organic additives in rubber vulcanisates using mass spectrometry, Lattimer et al. [22] used direct thermal desorption with three different ionisation methods El, Cl and FI. Also, rubber extracts were examinated directly by four ionisation methods (El, Cl, FD and FAB). The authors did not report a clear advantage for direct analysis as compared to analysis after extraction. Direct analysis was a little faster, but the extraction methods were considered to be more versatile. 

T-MS). The main direct mass-spectral methods are thermal desorption and pyrolysis mass spectrometry. Several factors favour the efficiency at which volatiles can be removed from a polymeric matrix ... 

SFE-GC-MS is particularly useful for (semi)volatile analysis of thermo-labile compounds, which degrade at the higher temperatures used for HS-GC-MS. Vreuls et al. [303] have reported in-vial liquid-liquid extraction with subsequent large-volume on-column injection into GC-MS for the determination of organics in water samples. Automated in-vial LLE-GC-MS requires no sample preparation steps such as filtration or solvent evaporation. On-line SPE-GC-MS has been reported [304], Smart et al. [305] used thermal extraction-gas chromatography-ion trap mass spectrometry (TE-GC-MS) for direct analysis of TLC spots. Scraped-off material was gradually heated, and the analytes were thermally extracted. This thermal desorption method is milder than laser desorption, and allows analysis without extensive decomposition. 

PLE pressurized liquid extraction, SPE solid phase extraction, UE ultrasonic extraction, DSPE dispersive solid phase extraction, SBSE stir bar sorptive extraction, TD-GC-MS thermal desorption-gas chromatography-mass spectrometry, LAS linear alkylbenzene sulfonates, CDEAs coconut diethanol amides, NPEOs nonylphenol ethoxylates, DP degradation products, SPC sulphenyl carboxylates, PCDD dibenzo-p-dioxins (PCDD), PCDF dibenzofurans, PCBs biphenyls... 

Rodil R, Moeder M (2008) Development of a method for the determination of UV filters in water samples using stir bar sorptive extraction and thermal desorption-gas chromatography-mass spectrometry. J Chromatogr A 1179(2) 81—88... 

Tan BL, Hawker DW, Muller JF, Tremblay LA, Chapman HF (2008) Stir bar sorptive extraction and trace analysis of selected endocrine disrupters in water, biosolids and sludge samples by thermal desorption with gas chromatography-mass spectrometry. Water Res 42 404 112... 

In this report we present NEXAFS results for the kinetics of ethylidyne formation. Previous data is scarce and comes mostly from thermal desorption (TDS) experiments (2). The only reported study of isothermal rates of reactions for this system was done by Ogle et. al. using secondary ion mass spectrometry (SIMS) (10). 

Thermal desorption mass spectrometry is a rapid technique for the determination of oil in soils and sediments [9]. This method exhibited lower analytical variance compared to Soxhlet extraction, i.e. followed by conventional analysis. The analysis time for wet soil samples was about 20min. 

Robbat et al. [42] carried out on-site detection of polyaromatic hydrocarbons in soils using thermal desorption gas chromatography-mass spectrometry on hexane extracts of soils. 

The thermal desorption gas chromatography-mass spectrometry [42] described in section 2.4.1.2 has been applied to the determination of polyaromatic hydrocarbons in sediments. 

Kester [5] has discussed the application of the purge and trap gas chromatographic method to the determination of aliphatic chloro-compounds in soil. Following methanol extraction of the soil the extract is gas purged and the purge gases trapped on a Tenax silica gel/ charcoal trap followed by thermal desorption from the trap and examination by gas chromatography and mass spectrometry. Compounds that have been determined by this method are listed in Table 5.1. 

Valter B, Ram MK, Nicolini C (2002).Thermal desorption high-resolution mass spectrometry of mixed self-assembled monolayers on gold. Langmuir. 18 1535-1541. 

With a focus on trace forensic detection of explosives, especially for use in counterterrorism and to counter narcotics investigations, Fetterolf et al. [75] evaluated the use of ion mobility-mass spectrometry for explosives determinations. In this, explosives residues were collected on a membrane filter by a special attachment on a household vacuum cleaner. Although subsequent thermal desorption and analysis required only 5 s, fimits of detection for most common explosives were as low as 200 pg. The persistence of explosives on hands and transfer to other surfaces were also examined as were post-blast residues of NG on fragments of improvised explosive devices constructed with double-based smokeless powder. Finally, postblast residue from C-4, Semtex, and other explosives was found by IMS analyses on items of forensic and evidentiary value. These few out of many examples demonstrate that mobihty spectrometers are well suited tools for laboratory and on-site investigations, before and after the use of explosives. 

Ion mobility spectrometry (IMS [43]). Solid phase microextraction (SPME) using a 100 pm polydimethylsiloxane (PDMS) SPME fibre was used for head-space sampling and preconcentration of volatile markers of cocaine, MDMA and marijuana (methyl benzoate, piperonal and terpenes, respectively) in cargo containers. Analysis was then performed by IMS after thermal desorption of the drug markers from the fibre into the IMS analyser. 

Bianchi AP, Varney MS, Phillips J. 1991. Analysis of industrial solvent mixtures in water using a miniature purge-and-trap device with thermal desorption and capillary gas chromatography-mass spectrometry. J Chromatogr 557(l-2) 429-439. 

Argon is analyzed by mass spectrometry (characteristic ion m/z 40) or by gas-solid chromatography. Its concentration can be increased by several times by selective adsorption over a suitable adsorbent followed by thermal desorption of the gas onto the GC injection port. 

The presence of cyanamides of Cd and Pb in films of (Cd,Pb)S was confirmed by thermal desorption mass spectrometry [23]. Cyanamide (H2CN2) is a product of the decomposition of thiourea and forms sparingly soluble metal salts. The metal cyanamide content of the film varied from ca. 5% up to ca. 20% (by weight). The presence of the cyanamides decreased the intensity of the XRD reflections, presumably due to poorer crystallization of the sulphides. Interestingly, the photosensitivity of the films increased with higher metal cyanamide content, although whether this was due specifically to the presence of the cyanamide or to its effect on the crystal growth was not known. 

Oezel, M.Z., Goegues, R, Lewis, A.C., (2006) Determination of Teucrium chamaedrys volatiles by using direct thermal desorption-comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry. J. Chromatogr All 14 164-169. 

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