Uniquely electrospraying

Another type of ion is formed almost uniquely by the electrospray inlet/ion source which makes this technique so valuable for examining substances such as proteins that have large relative molecular mass. Measurement of m/z ratios usually gives a direct measure of mass for most mass spectrometry because z = 1 and so m/z = m/1 = m. Values of z greater than one are unusual. However, for electrospray, values of z greater than one (often much greater), are quite coimnonplace. For example, instead of the [M + H]+ ions common in simple Cl, ions in electrospray can be [M + n-H]- where n can be anything from 1 to about 30. 

Electrospray is the softest mass spectrometry ionization technique and electrospray spectra therefore usually consist solely of molecular ions. Electrospray is unique, however, in that if the analyte contains more than one site at which protonation (in the positive-ion mode) or deprotonation (in the negative-ion mode) may occur, a number of molecular ions with a range of charge states is usually observed. For low-molecular-weight materials (< 1000 Da), the number of sites... 

API offers unique opportunities for the implementation of new sources or to develop new applications. Atmospheric pressure matrix assisted laser desorption (AP-MALDI) [21] can be mounted on instruments such as ion traps which were originally designed only for electrospray and LC-MS. New API desorption techniques such as desorption electrospray (DESI) [22] or direct analysis in real time (DART) [23] have been described and offer unique opportunities for the analysis of surfaces or of solid samples. 

Cr CNNi(tetren) 6](C104)9 is a red-purple solid, soluble in water-acetonitrile mixtures where the undissociated heptanuclear entity can be identified by electrospray ionization mass spectrometry. IR spectroscopy shows the presence of a unique /cn band at 2146 cm of the bridging cyano ligand and an intense band of the perchlorate anion at cr = 1090 cm The IR spectrum of the C-enriched compound prepared from K3[Cr( CN)6] displays a /cn band at 2103 cm The compound crystallizes in a trigonal system, space group R3, with parameters a = b = 15.274 A and c = 41.549 A. The magnetic properties indicate a ferro-... 

Because all library compounds must be monitored simultaneously, the compounds must be selected so that they have unique molecular weights. Also, one compound in the mixture should not suppress the ionization of another. Therefore, this approach is probably restricted to the screening of small combinatorial libraries that are similar in chemical structure and ionization efficiencies. Finally, the binding buffer used for affinity chromatography must be compatible with on-line APCI or electrospray mass spectrometry. This means that the mobile phase must be volatile and usually of low ionic strength (i.e., typically <40 mM for electrospray ionization). 

A variety of MS formats are widely accepted and applied in the pharmaceutical industry. The specific MS application is often defined by the sample introduction technique. The pharmaceutical applications highlighted in this article feature two types of sample introduction techniques dynamic and static. Dynamic sample introduction involves the use of high-performance liquid chromatography (HPLC) on-line with MS. The resulting liquid chromatography/mass spectrometry (LC/MS) format provides unique and enabling capabilities for pharmaceutical analysis. The electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) modes are the most widely used. Static sample introduction techniques primarily use matrix-assisted laser desorption/ionization (MALDI). ... 

Nawwar, M.A.M. Marzouk, M.S. Nigge, W. Linscheid, M. High-performance liquid chromatographic/electrospray ionization mass spectrometric screening for polyphenolic compounds of Epilobium hirsutum—The structure of the unique ellagitannin epilohamide. Mass Spectrom. 1997, 32, 645-654. 

Chemical characterization hypothesizes that certain molecules are unique and representative of individual microorganisms, and therefore the mass spectra can be characteristic of given species. A typical bacterial spectrum obtained by MALDI-TOF usually contains between 20 and 40 large peaks, mainly produced by proteins, phospholipids, and cyclic lipopeptides, in the MW range of 4—20 kDa.31 ESI is less frequently used samples containing intact cells can clog electrospray devices, and the formation of multiply charged species complicates the spectra. 

Sodeoka et al. have found fhat binuclear /z-hydroxo palladium complex 87 is an efficient catalyst of fhe asymmetric Mannich-type reaction of a-N-arylimino esters with SEE (Scheme 10.80) [226]. Mechanistic studies using NMR and electrospray ionization mass spectrometry suggest that a unique binuclear palladium-sandwiched enolate 88 is involved in fhe palladium-catalyzed reaction. 

In cases where the toxin is metabolized, excreted, or otherwise not available for immunological or chemical detection, it may be possible to verify an exposure to ricin or castor seeds for forensic purposes by detecting other unique components of the R. communis plant. PCR can detect residual castor seed DNA in most ricin preparations. Ricinine, an alkaloid (3-cyano-4-rnethoxy-A -rnethyl-2-pyridone) produced by castor seeds, has been proposed as a biomarker for ricin exposure the detection limit for ricinine by electrospray ionization tandem mass spectrometry is as low as 0.083 ng/mL in urine of exposed subjects (Johnson et al., 2005). 

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