Enhanced ionization

Vol. 136. Laser-Enhanced Ionization Spectrometry. Edited by John C. Travis and Gregory C. Turk... 

Triethylamine (TEA) is sometimes used as an additive for signal enhancement. However, in the positive ESI mode, TEA readily ionizes to give an intense [M + H]+ ion at miz 102. This then suppresses the ionization of the less basic compounds in the positive ESI mode. In the negative mode, TEA can enhance ionization for certain compounds because of its basic properties. 

Wayne DM, Hang W, McDaniel DK, Fields RE, Rios E, Majidi V (2002) The thermal ionization cavity (TIC) source elucidation of possible mechanisms for enhanced ionization efficiency. Inti J Mass Spectrom 216 41-57... 

Photothermal Spectroscopy Methods for Chemical Analysis. By Stephen E. Bialkowski Element Speclatlon in Bioinorganic Chemistry. Edited by Sergio Caroli Laser-Enhanced Ionization Spectrometry. Edited by John C. Travis and Gregory C. Turk Fluorescence Imaging Spectroscopy and Microscopy. Edited by Xue Feng Wang and Brian Herman... 

H. Intracluster Reactions Initiated through Photon Absorption Resonant Enhanced Ionization... 

Laser enhanced ionization spectroscopy and resonance ionization spectroscopy... 

Neuroactive steroids are comparatively polar compounds that, in most cases, are derivatized by a suitable reagent before being analyzed by GC/MS. It is essential to add functional groups that enhance ionization efficiency, decrease polarity, and increase volatility of the steroid, thus making it more easily detected by GC/MS. Suitable derivatization of neuroactive steroids also results in enhanced sensitivity and specificity of mass spectra. 

The polarization effects of metals have a substantial impact particularly in two areas the promotion of the hydrolysis and other nucleophilic reactions of chelated ligands and the enhanced ionization of coordinated acidic ligands. Their importance has encouraged extensive attacks on the effects. 

An isotope dilution mass spectrometric method involves the addition of a known quantity of Tc followed by chemical separation, purification, and measurement of the Tc/ Tc isotopic ratio . An improved technique has been developed for the analysis of Tc in environmental samples. After spiking with Tc the isolated technetium is concentrated onto anion exchange beads. Determination of as little as 1 pg has been achieved through the enhanced ionization efficiency afforded by the resin bead source ... 

One has to emphasize that MS also is associated with several drawbacks when it comes to bioactivity screening. First of all, the optimum, native conditions for bioactivity screening (pH 7.2, addition of 150 mM sodium chloride) are entirely incompatible with optimum conditions for MS detection which, for ESI-MS, typically require acidic pH values and the presence of organic modifiers to enhance ionization properties of the analytes. Assay development for MS-based assays therefore mainly requires the testing of different assay conditions, particularly the replacement of nonvolatile buffers with MS-compatible volatile buffers. Furthermore, it is essential to monitor ion suppression effects, for example, by the... 

Heptafluoro- 1-butanol can be added postcolumn to give a final concentration of 0.1 % (v/v) to enhance ionization efficiency during electrospray. Typically, a 2% (v/v) solution in mobile phase is added at 50 pl/min to the HPLC column effluent at 1 ml/min. Addition of this reagent is optional. 

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