The formation of [M–H]⁺ ions in N‐alkyl‐substituted thieno[3,4‐c]‐pyrrole‐4,6‐dione derivatives during atmospheric pressure photoionization mass spectrometry

Abstract

[M-H](+) ions were detected in all the TPD derivatives studied here under the special experimental conditions during APPI, using a halogenated benzene dopant, and TPD containing substituted N-alkyl side chains with a minimum of four carbon atoms. Density functional theory calculations showed that for [M-H](+) ions to be formed under these conditions, the loss of hydrogen molecules from the [M + H](+) ions is proposed to be necessary.

7-Hydroxy-4-phenyl-1, 2-dihydroquinoline derivatives: synthesis via one-pot, three-component reaction and structure elucidation

“…Surprisingly [M-H] + and M +∙ peaks were observed in almost all investigated compounds instead of [M+H] + peaks which are observed only in 5c (Figure S48) and 5d (Figure S49) spectra, this indicated that these type of compounds produce [M-H] + , [M-H-H 2 ] + , [M-H 2 ] + and M +∙ positive ions by this soft ionization technique ( Table 2 ). [M-H] + peak is observed in all spectra which may appear due to; a) transfer of hydrogen atom from radical cation of analyte or b) by hydride removal from neutral molecule of analyte, or c) removal of H 2 from protonated molecule of analyte [ 69 , 70 , 71 , 72 ] All these three mechanisms may occur simultaneously or not depending on the structure of analyte molecule [ 73 ]. M +∙ observed in spectra of 5b, 5d, 5h, 5k and 5m (Figures S47, S49, S53, S56 and S58) may be due to photoionization process.…”

“…ions by this soft ionization technique (Table2). [M-H] þ peak is observed in all spectra which may appear due to; a) transfer of hydrogen atom from radical cation of analyte or b) by hydride removal from neutral molecule of analyte, or c) removal of H 2 from protonated molecule of analyte[69,70,71,72] All these three mechanisms may occur simultaneously or not depending on the structure of analyte molecule[73]. M þ• observed in spectra of 5b, 5d, 5h, 5k and 5m (Figures S47, S49, S53, S56 and S58) may be due to photoionization process.…”

Reactive Olfaction Ambient Mass Spectrometry

“…No particular trend was observed except that the analyte with highest proton affinity dominated the spectrum for mixture samples. For hydrocarbon analytes, both M +• and [M – H] + species were often observed together. , …”

“…For hydrocarbon analytes, both M +• and [M − H] + species were often observed together. 52,53 Quantification and Direct Biofluid Analysis. As already shown, vapor pressure is not a limiting factor in contained nAPCI MS.…”

Analysis of low molecular weight compounds using MALDI‐ and LDI‐TOF‐MS: Direct detection of active pharmaceutical ingredients in different formulations

“…It was even possible to detect the deprotonated molecule ([M‐H] + ) at m / z 473.2, which is rather common for tertiary amines. The formation of [M‐H] + is considered to occur through three possible mechanisms: (1) hydrogen atom transfer from the analyte radical cation, (2) loss of H 2 from the protonated analyte, or (3) hydride abstraction from the neutral analyte molecule . These mechanisms could be occurring simultaneously or not, depending on the analyte molecular structure.…”