Hquid secondary ion mass spectrometry

Mass spectral analysis of quaternary ammonium compounds can be achieved by fast-atom bombardment (fab) ms (189,190). This technique rehes on bombarding a solution of the molecule, usually in glycerol [56-81-5] or y -nitroben2yl alcohol [619-25-0], with argon and detecting the parent cation plus a proton (MH ). A more recent technique has been reported (191), in which information on the stmcture of the quaternary compounds is obtained indirectly through cluster-ion formation detected via Hquid secondary ion mass spectrometry (Isims) experiments. 

Recent advances of mass spectrometry and chromatography, and their hyphenated technologies in lipidomics analyses have been reviewed by Li and coworkers [38]. Soft ionization techniques such hquid secondary ion mass spectrometry (LSI-MS) [39] and FAB [40] allowed the mass spectrometric analyses of polar thermally labile molecules of masses up to a few thousand daltons. Later, MALDI [41] and electrospray ionization (ESI) [42] permitted the direct analysis of native biomolecules within the megadalton masses without derivatization. 

D. M. Desiderio and X. Zhu, Quantitative analysis of methionine enkephalin and P-endorphin in the pituitary by hquid secondary ion mass spectrometry and tandem... 

Older soft ionization methods that are related to MALDl—such as fast atom bombardment (FAB), hquid secondary ion mass spectrometry (LSIMS), or field desorption (FD)— in principle have potential for the generation of intact gas-phase ions from noncovalent complexes. In particular, the extensive clustering often found in FAB-MS, which is generally thought of as a nuisance, can be viewed as evidence for this. However, the limitation of these methods lies in their inabiUty to ionize very large molecules. It is generally very difficult or impossible to obtain useful mass spectra from compounds with molecular weights above a few thousand daltons. For this reason, FAB-MS, LSIMS, and FD-MS only play a very minor role in this field. 

The use of separation techniques, such as gel permeation and high pressure Hquid chromatography interfaced with sensitive, silicon-specific aas or ICP detectors, has been particularly advantageous for the analysis of siUcones in environmental extracts (469,483—486). Supercritical fluid chromatography coupled with various detection devices is effective for the separation of siUcone oligomers that have molecular weights less than 3000 Da. Time-of-flight secondary ion mass spectrometry (TOF-sims) is appHcable up to 10,000 Da (487). 

Jabs, H.U., Assmann, G, Greifendorf, D., Benninghoven, A. (1986) High performance hquid chromatography and time-of-flight secondary ion mass spectrometry a new dimension in structural analysis of apolipoproteins. J. Lipid Res.,27, 613-621. 

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an extremely surface-sensitive analytical technique that uses a beam of hquid metal ions to probe the top one to three molecular layers of a sample, causing the emission of ions from the sample to be detected in a time-of-flight mass spectrometer, which gives detailed information about the specific molecules and atoms at a surfiice. 

Chace, D., Millington, D. (1994) Neonatal screening for inborn errors of metabohsm by automated hquid secondary ion tandem mass spectrometry. In New Horizons in Neonatal Screening, Proceedings of the 9th International Neonatal Screening Symposium, edited by Farriaux, J., Dhont, J. Amsterdam, The Netherlands Elsevier, pp. 373-377. 

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