Atmospheric pressure thermal desorption ionization

Paglia G, D Apolito O, Corso G. Precursor ion scan profiles of acylcarnitines by atmospheric pressure thermal desorption chemical ionization tandem mass spectrometry. Rapid Commun Mass Spectrom 2008 22 3809-3815. 

Thome FA, Heavner DL, Ingebrethsen BJ, Eudy LW, Green CR (1986) Environmental tobacco smoke monitoring with an atmospheric pressure chemical ionization mass spectrometer/mass spectrometer coupled to a test chamber. Proc 79th Annual Meet Air Pollution Control Assoc. Air Pollution Control Assoc, Pittsburgh, paper 86-37.6 Thompson CV, Jenkins RA, Higgins CE (1989) A thermal desorption method for the determination of nicotine in indoor environments. Environ Sci Technol 23 429-435 Thomson BA, Davidson WR, Lovett AM (1980) Applications of a versatile technique for trace analysis atmospheric pressure negative chemical ionization. Environ Health Perspect 36 77-84... 

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. 

El = electron ionization Cl = chemical ionization ES = electrospray APCI = atmospheric-pressure chemical ionization MALDI = matrix-assisted laser desorption ionization PT = plasma torch (isotope ratios) TI = thermal (surface) ionization (isotope ratios). 

Electrospray ionization [21] is one of the most widely utilized ionization techniques employed today for the analysis of thermally fragile molecules. As such, it has assumed an important role in the analysis of biologically important molecules. ESI is a desorption ionization technique. This means that ions are formed before or during the transition from the liquid phase and need not be volatilized in advance of the ionization event (as is the case for El, Cl, etc.). Like APCI and APPI, ESI occurs at atmospheric pressure outside the vacuum chamber of the mass spectrometer (Fig. 11.5). A solution of the analyte passes through... 

To perform mass spectrometry, one must make ions from neutral molecules. Ionization methods have advanced from the classic electron ionization (El), through chemical ionization, field desorption, fast atom bombardment (FAB), h 62 thermospray to the atmospheric pressure ionization (API) techniques currently favored. El is classic, but its is restricted to thermally stable, volatilizable compounds. Field desorption was always a specialized niche technique applicable to some larger compounds. Fast atom bombardment enjoyed a meteoric rise in use when it was first reported in 1981 but it has all but disappeared now, being replaced by the API tech-... 

Wu, J. et al., High-throughput cytochrome P450 inhibition assays using laser diode thermal desorption-atmospheric pressure chemical ionization-tandem mass spectrometry, Anal. Chem., 79, 4657, 2007. 

Laser desorption atmospheric pressure chemical ionization (LD-APCI) combines a laser system and an APCI source to desorb and ionize small chemical compounds on TLC plates (Figure 7.3) [29]. Vaporization and desorption of analytes from the TLC gel bed was achieved by surface heating with a continuous wave (CW) diode laser operated at 808 nm. It was reported that a laser power density of 10 W/cm enables desorption of analytes from white TLC plates. Furthermore, the application of a graphite suspension (10 mg/mL in isopropanol) on the TLC gel decreased the CW laser power required for analyte desorption to 10" W/cm. Thermally desorbed analytes were postionized by reacting with charged species generated by corona discharge of the air. The TLC LD-APCI/MS approach was first used to characterize... 

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