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Desorption pressure

Direct analysis of solid samples or analytes present on solid surfaces without any sample preparation has always been a topic of interest. Desorption electrospray ionization (DESI) is an atmospheric pressure desorption ionization method introduced by Cooks et al., producing ions directly from the surface to be analyzed, which are then sampled with the mass spectrometer [22, 37]. DESI is based on charged liquid droplets that are directed by a high velocity gas jet (in the order of 300 m s ) to the surface to be analyzed. Analytes are desorbed from the surface and analyzed by mass spectrometer (Eig. 1.15). [Pg.20]

The oxygenated complex desorbed molecular oxygen on heating under reduced oxygen pressure. Desorption of oxygen, i.e. regeneration of the ferroheme complex,... [Pg.50]

Huikko, K., Oestman, P., Sauber, C., Mandel, F., Grigoras, K., Franssila, S., Kotiaho, T., and Kostiainen, R. (2003). Feasibility of atmospheric pressure desorption/ionization on silicon mass spectrometry in analysis of drugs. Rapid Commun. Mass Spectrom. 17 1339-1343. [Pg.357]

The outlet gas composition is not constant and depends on the level of pressure. Desorption of the high-molecular weight hydrocarbons happens mainly for pressure lower than 1 MPa. Between 3.5 MPa and 1 MPa, the equilibrium conditions between the gas and the adsorbed phase entail values of the different ratios systematically lower than 1. This is especially pronounced for the /-butane and the / -pentane. [Pg.74]

From the time of the second edition published in 2001 until now, much progress has been achieved. Several techniques have been improved, others have almost disappeared. New atmospheric pressure desorption ionization sources have been discovered and made available commercially. One completely new instrument, the orbitrap, based on a new mass analyser, has been developed and is now also available commercially. Improved accuracy in low-mass determination, even at low resolution, improvements in sensitivity, better detection limits and more efficient tandem mass spectrometry even on high-molecular-mass compounds are some of the main achievements. We have done our best to include them is this new edition. [Pg.502]

The adsorption isotherm starts at a low relative pressure. At a certcdn minimum pressure, the smallest pores will be filled with liquid nitrogen. As the pressure is increased still further, larger pores will be filled and near the saturation pressure, all the pores are filled. The total pore volume is determined by the quantity of gas adsorbed near the saturation pressure. Desorption occurs when the pressure is decreased from the saturation pressure. The majority of physisorption isotherms may be grouped into six types [9]. Due to capillary condensation, many mesoporous systems exhibit a distinct adsorption-desorption behaviour which leads to characteristic hysteresis loops (Type IV and V isotherms) whose shape is related to pore shape. Type I isotherms, characterised by a plateau at high partial pressure, are characteristic of microporous samples. A typical isotherm, representative of a mesoporous sample is given in Fig. 4.6, with a schematic representation of the adsorption steps. [Pg.80]

Traditionally, products and adsorbates had to be volatile enough so that they could be carried from the cell into the mass spectrometer, either by headspace sampling, or, more commonly for near-simultaneous analysis (referred to as differential electrochemical mass spectrometry), across a nanoporous, gas-permeable membrane (e.g., Teflon) supported at the tip of a microcapillary placed close to the electrode. Alternatively, a Pt-coated membrane electrode can be used. But the advent of the so-called soft atmospheric pressure desorption/ionization techniques associated with liquid chromatography-mass spectrometry has allowed the sampling of the solvent and involatile solutes directly. The spectra are more... [Pg.4454]

A turning point in atmospheric pressure desorption-ionization techniques for the analysis of chemical compounds was reached very recently with the introduction of DESI (U.S. Patent Application 20050230635). In this approach, charged droplets from an electrosprayed solution are directed toward a solid sample by means of a high-velocity gas stream. The charged droplets ablate the exterior of the sample, removing and ionizing chemical compounds present on the surface. Accordingly, DESI permits the direct analysis of condensed-phase samples with minimal or no sample preparation. [Pg.946]

Most of the mass spectrometry analyses are conducted under vacuum environment. However, ambient mass spectrometry is a rapidly growing field that provides fast and direct analysis of solid sample surfaces or liquid samples introduced on a suitable surface (Alberici et al. 2010 Weston 2010 Huang et al. 2010 Chen et al. 2010). For that, different ambient ionization MS methods, such as atmospheric pressure desorption/ionization on porous silicon (AP-DIOS) (Huikko et al. 2003), desorption electrospray ionization (DESI) (Takats et al. 2004), direct analysis in real time (DART) (Cody et al. 2005), desorption atmospheric pressure chemical ionization (DAPCI) (Takats et al. 2005), and desorption atmospheric pressure photoionization (DAPPI) (Haapala et al. 2007), have been successfully used in the direct analysis of compounds fi"om various samples, such as body fluids (Cody et al. 2005 Chen et al. 2006), finiits, plant leaves (Luosujarvi et al. 2010), milk (Yang et al. 2009), banknotes (Cody et al. 2005), textiles (Cody et al. 2005 Chen et al. 2007), and pharmaceutical formulations (Ifa et al. 2009 Gheen et al. 2010), just to mention a few, without any sample pretreatment. [Pg.768]

Ostman P, Pakaiinen JMH, Vainiotalo P, Franssila S, Kostiainen R, Kotiaho T (2006) Minimum proton affinity for efficient ionization with atmospheric pressure desorption/ionization on silicon mass spectrometry. Rapid Commun Mass Spectrom 20 3669-3673... [Pg.778]

Pihlainen K, Grigoras K, Franssila S, Ketola R, Kotiaho T, Kostiainen R (2005) Analysis of amphetamines and fentanyls by atmospheric pressure desorption/iortization on silicon mass spectrometry and matrix-assisted laser desorption/iortization mass spectrometry and its application to forensic analysis of drug seizures. J Mass Spectrom 40 539-545... [Pg.778]

PDI), the sample is dissolved in a volatile solvent and deposited on a nitrocellulose target material, which is subsequently bombarded with the fission fragments [33-37]. Maity mass spectra of PDl-MS show the occurrence of [M+Na]+ next to [M+H]+ [37], PDl-MS has been extensively used for the analysis of biological macromolecules, but has been superseded by MALDl. Atmospheric-pressure desorption ionization methods are briefly discussed in Sect. 7.2.7. [Pg.211]

In addition to DESI and AP-MALDI, a large variety of other, sometimes closely related, atmospheric-pressure desorption ionization techniques have been introduced in the past decade, connected to a huge number of acronyms. Van Beikel et al. [76] tried to classify these emerging techniques into four categories, i.e., (1) thermal desorption ionization, (2) laser desorption/ablation ionization, (3) liquid-jet and gas-jet desorption ionization, and (4) hquid extraction surface sampling probe ionization. [Pg.217]

Another interesting development in the field of synthetic polymer charaeteriza-tion is the emergence of ambient-pressure desorption ionization techrriques such as desorption electrospray ionization mass spectrometry (DESI-MS) and many... [Pg.325]

Eqs. (I l-S) and (11-6) give the velocities of adsorption front during high pressure adsorption and low pressure desorption, vh and vl denote linear gas velocities at high pressure and low pressure flow. [Pg.251]

Pressure Swing Adsorption (PSA) makes use of the fact that the amount of adsorbate, which can be deposited on the adsorbent, increases with increasing pressure. Adsorption occurs at high pressure, desorption at low pressure. This technique is applied for the adsorptive recovery of Oj and Nj from air. [Pg.18]

Figure 11-3. Nitrogen adsorption isotherms at 77 K, for a series of pure silica aerogels first densified under different isostatic pressures. Desorption isotherms were left out for clarity (Pirard, 2000b). Figure 11-3. Nitrogen adsorption isotherms at 77 K, for a series of pure silica aerogels first densified under different isostatic pressures. Desorption isotherms were left out for clarity (Pirard, 2000b).

See other pages where Desorption pressure is mentioned: [Pg.309]    [Pg.513]    [Pg.173]    [Pg.294]    [Pg.24]    [Pg.309]    [Pg.155]    [Pg.173]    [Pg.1548]    [Pg.309]    [Pg.1547]    [Pg.448]    [Pg.59]    [Pg.159]    [Pg.690]    [Pg.282]    [Pg.253]    [Pg.236]    [Pg.220]    [Pg.270]    [Pg.679]    [Pg.348]    [Pg.216]    [Pg.253]    [Pg.102]    [Pg.245]    [Pg.436]   
See also in sourсe #XX -- [ Pg.317 ]




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