Liquid secondary ionization mass spectrometry

Lang SR, Staudenmann W, James P, Manz HJ, Kessler R, Galli B, Moser HP, Rummelt A, Merkle HP (1996) Proteolysis of human calcitonin in excised bovine nasal mucosa elucidation of the metabolic pathway by liquid secondary ionization mass spectrometry (LSIMS) and matrix assisted laser desorption ionization mass spectrometry (MALDI). Pharm Res 13 1679-1685. 

The principle of FAB, less frequently referred to as liquid secondary ionization mass spectrometry (LSIMS), is very similar to secondary-ion mass spectrometry (SIMS). However, FAB utilizes a liquid matrix, such as glycerol, in which a sample is dissolved. The matrix is used to enhance sensitivity and ion current stability. 

Two-dimensional NMR spectroscopy ((double quantum fdtering (DQF), correlation spectroscopy (COSY), hetero-nuclear multiple quantum correlation (HMQC), heteronuclear multiple bond correlation (HMBC)) as well as liquid secondary ionization mass spectrometry (LSI MS) and UV-Vis spectroscopies were used to establish crown structures of TTFs 33 ( =l-3). In the case of the macrocycle 33 ( = 1), two protons of each methylene group of the SCH2CH2O fragments were not identical and gave an AA BB system. This observation was in accordance with the expected low conformational mobility of the polyether bridge in ( )-33 ( = 1) as compared with (Z)-33 ( = 1). The macrocycle ( )-33 ( = 2) behaved similarly to ( )-33 ( =1), whereas the protons under discussion were equivalent in ( )-33 ( = 3) <2001CFJ447>. 

C. Dass and P. Mahalakshmi, Amino acid seqnence determination of phospho-enkephalins using liquid secondary ionization mass spectrometry. Rapid Commun. Mass Spectrom. 9, 1148-1154 (1995). 

Aberth, W.H. Burlingame, A.L. Effect of Primary Beam Energy on the Secondary-Ion Sputtering Efficiency of Liquid Secondary-Ionization Mass Spectrometry in the 5-30-KeV Range. Anal. Chem. 1988,60, 1426-1428. 

Mass Spectrometry. Mass spectrometry holds great promise for low-level toxin detection. Previous studies employed electron impact (El), desorption chemical ionization (DCI), fast atom bombardment (FAB), and cesium ion liquid secondary ion mass spectrometry (LSIMS) to generate positive or negative ion mass spectra (15-17, 21-23). Firm detection limits have yet to be reported for the brevetoxins. Preliminary results from our laboratory demonstrated that levels as low as 500 ng PbTx-2 or PbTx-3 were detected by using ammonia DCI and scans of 500-1000 amu (unpublished data). We expect significant improvement by manipulation of the DCI conditions and selected monitoring of the molecular ion or the ammonia adduction. 

Note. Abbreviations g.l.c., gas-liquid chromatography e.i.-m.s., electron-impact mass spectrometry c.i.-m.s., chemical-ionization mass spectrometry h.p.l.c., high-performance liquid chromatography h.p.a.e., high pH anion-exchange f.a.b.-m.s., fast-atom-bombardment mass spectrometry l.s.i.-m.s., liquid secondary-ion mass spectrometry n.O.e., nuclear Overhauser enhancement. Details of these methodologies are given in Ref. (3). 

Fast-atom bombardment (FAB) and liquid secondary-ion mass spectrometry (LSIMS) methods make up the category of the particle bombardment ionization. In both methods the analyte is dissolved in a liquid such as glycerol, thioglycerol, m-nitrobenzyl alcohol, or diethanolamine and about 1 1 is placed on a... 

Mass spectrometer or tandem mass spectrometer (JEOL, Micromass, MAT from ThermoFinnigan) equipped with direct insertion probe and fast atom bombardment (FAB) or liquid secondary ion mass spectrometry (LSIMS) for LC/MS or flow injection using continuous-flow FAB, mass spectrometer must be equipped with continuous-flow ionization source... 

Liquid Secondary Ion Mass Spectrometry Linear Time of Flight Matrix-Assisted Laser Desorption Matrix-Assisted Laser Desorption/Ionization Molecular Beam... 

Mass spectra were obtained with the following conditions ES (Electrospray) on anLCTOF MICROIVIASS El (Electronic Impact) and D/CI (Desorption/Chemical Ionization ammonia) on a SSQ7000 FINNIGAN LSIMS (Liquid Secondary Ion Mass Spectrometry) with a SCIEX PERKIN ELMER (Cs 35 KeV 3-nitrobenzyl alcohol matrix). 

There are numerous other ionization methods, but they have limited applications. Fast atom bombardment (FAB), also known as liquid secondary ion mass spectrometry (LSIMS), was one of the early methods developed for the ionization of polar molecules. FAB is based on bombarding analytes in a matrix of low volatility, such as glycerol, with accelerated energetic neutral atoms (argon or xenon) or ions (cesium) that wiU sputter [M + H]+ ions from the surface. Although of major importance during its heyday, FAB has been superseded by ESI. 

See also Mass Spectrometry Overview Ionization Methods Overview Eiectron Impact and Chemical Ionization Atmospheric Pressure Ionization Techniques Electrospray Liquid Secondary Ion Mass Spectrometry Matrix-Assisted Laser Desorption/lonization Mass Separation Ion Traps Time-of-Flight. 

Chemical reactions at the gas-surface interface can be followed by monitoring gas-phase products with, for example, a mass spectrometer, or by directly analyzing the surface with a spectroscopic technique such as Auger electron spectroscopy (AES), photoelectron spectroscopy (PES), or electron energy loss spectroscopy (EELS), all of which involve energy analysis of electrons, or by secondary ionization mass spectrometry (SIMS), which examines the masses of ions ejected by ion bombardment. Another widely used surface probe is low-energy electron diffraction (LEED), which can provide structural information via electron diffraction patterns. At the gas-liquid interface, optical reflection elHpsometry and optical spectroscopies are employed, such as Eourier transform infrared (ET IK) and laser Raman spectroscopies. 

Of the two related techniques, FAB found far greater use in studies of enantioselective discrimination as compared to other desorption/ionization methods, such as MALDI and secondary ion mass spectrometry (SIMS). Chan and coworkers demonstrated enantiodiscrimina-tion of amino acids by a-, P-, and y-cyclodextrins using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) [28]. The observed levels of enantioselectivity were found to be dependent on the size of cyclodextrin cavities, as well as on the length and functionality of the amino acid side chain. Vairamani and coworkers demonstrated discrimination of amino acid methyl esters using various monosaccharide hosts by liquid secondary ion mass spectrometry (LSIMS) [29]. It is curious that more work has not been done using these sources. MALDI, in particular, is a simple and straightforward technique. Various researchers have demonstrated the observation of noncovalent complexes [30-32], for example, between peptides and proteins, but relatively little work has been performed that focuses on studying enantioselective noncovalent interactions by MALDI-MS. 

Chapter 6, titled Selection of Ionization Methods of Analytes in the TLC-MS Techniques provides an overview of mass spectrometric techniques that can be coupled with TLC and act as specific detectors in this hyphenated approach. The mass spectrometric techniques discussed in this chapter are secondary mass spectrometry (SIMS), liquid secondary ion mass spectrometry (LSIMS), fast atom bombardment (FAB), matrix-assisted laser desorption/ionization (MALDI), atmospheric pressure matrix-assisted laser desorption/ionization (AP-MALDI), electrospray ionization (ESI), desorption electrospray ionization (DESI), electrospry-assisted laser desorption/ionization (ELDI), easy ambient sonic spray ionization (EASI), direct analysis in real time (DART), laser-induced acoustic desorption/electrospray ionization (LIAD/ESI), plasma-assisted multiwavelength laser desorption/ionization (PAMLDI), atmospheric-pressure chemical ionization (APCI), and dielectric barrier discharge ionization (DBDI). For the sake of illustration, the authors introduce practical examples of implementing TLC separations with detection carried out by means of individual mass spectrometric techniques for the systematically arranged compounds belonging to different chemical classes. 

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