The fragmentation of negative ions generated by electron capture negative ion mass spectrometry: A review with new data

Abstract

Electron capture negative ion (ECNI) mass spectrometry is a technique used to detect trace levels of electrophilic compounds in complex matrices. ECNI mass spectra can also provide information regarding molecular structure. In this paper, current knowledge regarding the modes of negative ion formation under ECNI conditions is presented. Types of negative ions that have been observed in ECNI mass spectra are summarized based upon spectra that have appeared in the literature and upon the spectra of over 350 compounds that were measured in our laboratory. Factors that influence molecular ion stability and sensitivity to isomeric structures are addressed.

Gas chromatography coupled to electron capture negative ion mass spectrometry with nitrogen as the reagent gas – an alternative method for the determination of polybrominated compounds

“…Methane is almost exclusively used as the reagent gas in GC/ECNI‐MS 5, 8. A disadvantage of methane, however, is that it causes carbonization of the ion source,9, 10 which gives rise to high instrumental maintenance and short filament lifetimes 11.…”

Organic Iodine Compounds in Fine Particulate Matter from a Continental Urban Region: Insights into Secondary Formation in the Atmosphere

“…Due to their high electrophilicity, organohalogens have high selectivity and sensitivity when using an ECNI source. 25 Therefore, unknown organobromines and organochlorines can be detected in complex mixtures of environmental samples using an ECNI source with isotopic ratios (i.e., ∼1:1 for 79 Br: 81 Br and ∼3:1 for 35 Cl: 37 Cl). 15,16 However, this strategy is not applicable to organoiodines because iodine has only one natural stable isotope of 127 I. Alternatively, we used a high-resolution MS to screen I − , which is the major fragment of OICs generated by ECNI due to the fragile C−I bond and electrophilicity of iodine atom.…”

Oxidation reactions of dibenzothiophene subjected to negative chemical ionization with oxygen

“…[5]], as well as ions stemming from a complete oxidative degradation of 1 (e.g.. The ion [M + O 2 ] -, could either be a cluster ion between M and O 2 ' [9,10] (in which case it would belong to the ion-molecule-reaction products; the al- [30] can be excluded for reasons given below), or an oxidation product of 1 such as the corresponding sulfone 3 [3] or its rearrangement product, the sulfinate 4. In this case a surface-catalyzed reaction has to be taken into account.…”

“…These spectra differ grossly from those where 02 only plays a partial role as a contaminant: v. Ardenne et al [6], using a low pressure discharge in as side-products of aromatic compounds when nonreactive reagent gases are used [9,10]. Their genesis is explained by ion-molecule reactions of sample molecules with 0-' or OH-derived from trace amounts of O 2 and H 20 present in the ion source [9,10]. [M -H]-ions may either be formed by dissociative electron capture or by deprotonation by basic species such as 0-' or OH- [9,10].…”

“…Their genesis is explained by ion-molecule reactions of sample molecules with 0-' or OH-derived from trace amounts of O 2 and H 20 present in the ion source [9,10]. [M -H]-ions may either be formed by dissociative electron capture or by deprotonation by basic species such as 0-' or OH- [9,10]. Besides 0-' (which in the experiments of Hunt et al [2) was removed by the addition of H 2), the basic reagent ions°2 ' and OH- [11] are present in the 02 plasma and it is, therefore, rather surprising that M-' (m/z 184) should be observed [2] in the NO(02) mass spectrum of 1, whereas [M -H]-and not M-' is formed [8] even when electron capture promoting hydrocarbon reagent gases such as i-C 4 H lO are used.…”