Effect of nitro groups and alkyl chain length on the negative ion tandem mass spectra of alkyl 3-hydroxy-5-(4′-Nitrophenoxy) and alkyl 3-hydroxy-5-(2′, 4′-dinitrophenoxy) benzoates

Abstract

Tandem mass spectrometric behaviour was studied for a small combinatorial library of alkyl 3-hydroxy-5-(4'-nitrophenoxy) benzoates (A1-A5) and alkyl 3-hydroxy-5-(2', 4'-dinitrophenoxy) benzoates (B1-B5). The spectra were recorded by negative ion electrospray low-energy collision induced dissociation (CID) tandem mass spectrometry. The product ion spectra of [M - H](-) of the benzoates A1-A5 are similar, as are those of benzoates B1-B5. However, the spectra of the B series compounds differ significantly from those of the A series owing to the second electron-withdrawing nitro substituent in the B compounds. In addition, the length of the alkyl chain has an effect on the fragmentation. However, both series of compounds exhibit an abundant nitrophenoxy ion formed by the loss of 3-hydroxybenzoate. This is at m/z 138 in A1-A5 and at m/z 183 in B1-B5. A precursor ion scan of the nitrophenoxy ion provides a rapid method to identify the synthesised compounds in this type of combinatorial mixture. Copyright 1999 John Wiley & Sons, Ltd.

High-Performance Thin-Layer Chromatography Method for Assessment of the Quality of Combinatorial Libraries, and Comparison with Liquid Chromatography−Ultraviolet−Mass Spectrometry

“…Thus, "cleave and analyze" methods with mass spectrometry (MS) are routinely used instead in the quality control of synthesis. The MS methods mostly are either flow injection analysis (FIA-MS) 5,8,17 or liquid chromatography-MS (LC-MS) combined with UV detection. 5,6 FIA-MS is a highly efficient method for rapid qualitative assessment of the synthesis library.…”

“…Thus, “cleave and analyze” methods with mass spectrometry (MS) are routinely used instead in the quality control of synthesis. The MS methods mostly are either flow injection analysis (FIA-MS) ,, or liquid chromatography−MS (LC−MS) combined with UV detection. , FIA-MS is a highly efficient method for rapid qualitative assessment of the synthesis library. However, the purity assessment is normally done by LC−MS, since impurities may suppress the ionization process in FIA-MS, especially electrospray ionization, reducing the reliability of the analysis.…”