Mass spectrometry sample conditioning

Z. Takats, J. M. Wiseman, B. Gologan, and R. G. Cooks. Mass Spectrometry Sampling Under Ambient Conditions with Desorption Electrospray Ionization. Science, 306(2004) 471-473. 

Takats, Z. Wiseman, J. M. Gologan, B. Cooks, R. G. Mass spectrometry sampling under ambient conditions with desorption electrospray... 

Local considerations. There are many other local factors which dictate the path of method development. An increasingly common example is the development of a method which, as well as serving for quantitation, may be directly transferred to HPLC-mass spectrometry (commonly referred to as LC-MS) to allow the identification of minor components in a sample. This is achievable if the desired separation can be obtained using an ammonium acetate buffer instead of the more usual phosphate buffer. On the other hand, if it was intended that the unknown minor components should be isolated in milligram quantities to allow full structural elucidation using techniques such as H NMR as well as mass spectrometry, then conditions would be developed especially for the isolation unless the conditions for quantitative work coincidentally also lent... 

Approximately 10% Of the sediment and organism samples were analyzed by combined high resolution gas chromatography-mass spectrometry. Samples were analyzed on a Hewlett-Packard Model 5992B computerized GC-MS system (Hewlett-Packard, Avondale, PA) equipped with a 30 m DB-5 fused silica capillary column. Running conditions were a follows carrier gas = helium column flow... 

Takats Z, Wiseman JM, Gologan B, Cooks RG (2004) Mass spectrometry sampling under ambient conditions with desorption electrospray ionization. Science 306 471-473 Takats Z, Cotte-Rodriguez I, Talaty N, Chen H, Cooks RG (2005) Direct, trace level detection of explosives on ambient surfaces by desorption electrospray ionization mass spectrometry. Chem Commun 15 1950-1952... 

Takats, Z., Wiseman, J.M., Gologan, B. and Cooks, R.G., Mass spectrometry sampling under ambient conditions with desorption electrospray ionization. Science, 306, 471-473 (2004). Cody, R.B., Laramee, J.A. and Durst, H.D., Versatile new ion source for the analysis of materials in open air under ambient conditions. Anal. Chem., 77, 2297-2302 (2005). 

If a sample solution is introduced into the center of the plasma, the constituent molecules are bombarded by the energetic atoms, ions, electrons, and even photons from the plasma itself. Under these vigorous conditions, sample molecules are both ionized and fragmented repeatedly until only their constituent elemental atoms or ions survive. The ions are drawn off into a mass analyzer for measurement of abundances and mJz values. Plasma torches provide a powerful method for introducing and ionizing a wide range of sample types into a mass spectrometer (inductively coupled plasma mass spectrometry, ICP/MS). 

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. 

The control of materials purity and of environmental conditions requires to implement physico-chemical analysis tools like ESC A, RBS, AUGER, SEM, XTM, SIMS or others. The principle of SIMS (Secondary Ion Mass Spectroscopy) is shown in Eig. 31 an ion gun projects common ions (like 0+, Ar+, Cs+, Ga+,. ..) onto the sample to analyze. In the same time a flood gun projects an electron beam on the sample to neutralize the clusters. The sample surface ejects electrons, which are detected with a scintillator, and secondary ions which are detected by mass spectrometry with a magnetic quadrupole. 

In the vast majority of GC-MS applications, the chromatographic conditions employed have little or no effect on the operation of the mass spectrometer. This means that the spectrometer may be tuned for optimum performance and a number of samples containing different analytes can be analysed without operator intervention. This is not the case with LC-MS where the chromatographic conditions will invariably have a significant, compound-dependent, effect on the mass spectrometry conditions required to obtain useful analytical data. 

The o-dichlorobenzene extracts were combined and analyzed by GLC. Four peaks were observed under standard GLC conditions in the 10 to 15 min retention time range which is characteristic of hexachloro-dibenzo-p-dioxins (sample 1 in Table IV). The mixture was fractionally sublimed (120° to 175°G/1 mm). The major crop was harvested at 175 °G and recrystallized from anisole. Analysis of this material by GLG indicated that two isomeric hexachlorodibenzo-p-dioxins were present (sample 2). Overall yield (1.5 grams) of the product was 1-3% at 99+% purity, as determined by GLG and mass spectrometry. 

The pretreatment conditions were the same as those for IR study of adsorbed pyridine. The sample pretreated in a vacuum was exposed to ca. 300Torr D2 at different temperatimes for 1 h. After cooling to room temperature, the sample was outgassed for 10 min prior to TPD run. TPD was run at a heating rate of lOK min 1, and the desorbed gases were analyzed by mass spectrometry. 

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