The ion‐trap mass spectrometer in ion structure studies. The case of [MH]⁺ ions from chalcone

Abstract

The study of electron ionization (EI) induced decomposition patterns is usually undertaken by extensive metastable-ion investigations, mainly depending on spectra of the unimolecular decomposition of parent ions carried out in double-focusing instruments.By such an approach, in the last decades most of the definitive data on ion structures and on the mass spectrometric behaviour of many classes of compounds have been achieved. Unfortunately, single-quadrupole analysers do not give any definitive information on the unimolecular decomposition pathways of selected species; only by collision experiments in triple-stage quadrupolar systems can such data be obtained.','The ion-trap mass spectrometer3 (ITMS) offers a particularly interesting mass spectrometric approach due to its ability to store ions for further experiments, first of all being mass analysis. In particular, the use of a supplementary AC voltage (the so-called 'tickle' voltage) leads to effective collision-induced decompositions of preselected ionic species, even in cases where the energy deposition into the stored ionic species is lower than that usually observed in high-energy collision experiments.For these reasons ITMS seems to be highly promising for ion structure investigations as an alternative to the more complex (and more expensive) systems such as double-focusing sector instruments and triple-stage quadrupoles. In other words, what is usually obtained by the study of natural or collision-induced decomposition in multiple-stage analysers, is achieved in the ITMS by a simple, single-stage device by means of time separation of the different steps, namely electron ionization, ionic species isolation, collision of the preselected ions, mass analysis and detection of the collisioninduced decomposition products.Following our previous mass s ectrometric investigations of flavonoid cornpounds?'in this paper we will discuss the data obtained by ITMS on structure investigation of [M -HI+ ions of chalcone (2-propen-1-ona-1,3-diaphenyl) (l), whose EI mass spectrum has + Partially and preliminarily communicated at the European Meeting on Tandem Mass Spectrometry, Manchester UK, 9-11 July 1990.* Author to whom correspondence should be addressed.already been reported together with those of some of its derivatives.6-8 In such early papers the major fragmentation pathways and rearrangement processes were used to determine the type of chalcone and, in some cases, the position of substituents on the molecular skeleton. Some disagreement was expressed concerning the structure assignment of their [M -H]+ species.Ronayne and co-workers' postulated that the commonly observed intense [M -H]+ ion of chalcone was due to the loss of hydrogen from ring A in the resonance-stabilized flavylium ion structure a. The same mechanism was also proposed by Van

An unexpected methyl loss observed in electron ionization of chalcones

“…For the analysis of product ions, the precursor ion was selected using the tandem mass spectrometry (MS/MS) scan function and dynamically programmed scans as described previously. 4 Chalcone (1) was synthesized and purified according to the literature. 4 Its purity level (99%) was checked by gas chromatography/mass spectrometry (GC/MS) and the only impurities present were benzaldehyde and acetophenone employed as synthons for 1.…”

“…Previous researches on the mass spectrometric behaviour of flavonoids (in particular on flavones 1 , flavanones 2 , naphtoflavones 3 and chalconoids 4,5 ) led us to describe new fragmentation processes and some decomposition mechanisms different from those previously suggested. [6][7][8][9][10][11][12] In particular, in the case of chalcone (1) and some of its derivatives, structure a of Scheme 1 for the [MÀH] species was proved on the basis of metastable ion studies, collisional experiments and 2 H and 13 C-labelled compounds.…”

“…4 Chalcone (1) was synthesized and purified according to the literature. 4 Its purity level (99%) was checked by gas chromatography/mass spectrometry (GC/MS) and the only impurities present were benzaldehyde and acetophenone employed as synthons for 1. …”

Collisional spectroscopy approaches in the characterization of 7‐α‐ and 7‐β‐hydroxycholesterol

“…The 70eV mass spectra of 7-a-and 7-8-selected following a method described elsewhere , 14 at hydroxycholesterol (compounds 1 and 2) are practically mlz 384 for compounds 1 and 2, were irradiated for ~uperimposable. '~ Contrary to this, the CAD MIKE spectra of the M+' ions of 1 and 2, reported in Fig.…”

CHEMICAL COMPOSITION OF ESSENTIAL OIL OF BACCHARIS SALICIFOLIA (RUIZ & PAVON) PERS. AND ANTIBACTERIAL ACTIVITY

“…For the analysis of product, the collision inducted detection (CID) method was used. The precursor was selected using tandem mass spectrometry (MS/MS) scan standard function, with 0.5 daltons peak-widths for the parent ion and dynamically programmed scans, as described previously 9 . The main components detected in the samples here analyzed were: α-pinene (6.6x10-4 %), camphene (8.2x10-4 %), β-pinene (4.06x 10-3 %), α-phellandrene (0.0272 %), α-cubebene (5.176 %), β-cariophyllene (65.16 %), 6,9-guaiadiene (5.18 %), germacrene-D (6.6 %) and germacrone (17.85 %) which represent a 99.99 % of the total area.…”