Radical cation formation in characterization of novel C3‐symmetric disks and their precursors by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Lou, Xianwen; Hout, Kelly P. van den; Houtem, Michel H. C. J. van; Dongen, Joost L. J. van; Vekemans, Jef A. J. M.; Meijer, E. W.

doi:10.1002/jms.1025

Cited by 9 publications

(8 citation statements)

References 43 publications

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“…A closer inspection of this spectrum reveals the presence of sodium and potassium adducts ( m/z 150 and 166, respectively) but these are less abundant, however, than the radical cation and the protonated molecule. The formation of radical ions under MALDI conditions is not uncommon, as previously reported by Lou et al 24. These authors attributed the formation of radical cations during MALDI of trialkoxy anilines and oligo‐peptide anilides to the low ionization energy (IE) of anilines.…”

Section: Resultssupporting

confidence: 53%

Titanium dioxide anatase as matrix for matrix‐assisted laser desorption/ionization analysis of small molecules

Castro

Madeira

Nunes

et al. 2008

Rapid Comm Mass Spectrometry

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The use of inorganic species as assisting materials in matrix-assisted laser desorption/ionization (MALDI) analysis is an alternative approach to avoid interfering matrix ions in the low-mass region of the mass spectra. Reports of the application of inorganic species as matrices in MALDI analysis of small molecules are, however, scarce. Nevertheless, titanium dioxide (TiO(2)) powder has been reported to be a promising matrix medium. In this study we further explore the use of TiO(2) as a matrix for the MALDI analysis of low molecular weight compounds. We present results showing that nanosized TiO(2) anatase and TiO(2) rutile perform better as MALDI matrices than a commercial TiO(2) anatase/rutile mixture. Moreover, when using nanosized TiO(2) anatase as a matrix, high-quality mass spectra can be obtained with strong analyte signals and weak or non-existing matrix interference ions. Furthermore, our results show that the phase type plays an important role in the application of TiO(2) as a MALDI matrix.

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Section: Resultssupporting

confidence: 53%

Titanium dioxide anatase as matrix for matrix‐assisted laser desorption/ionization analysis of small molecules

Castro

Madeira

Nunes

et al. 2008

Rapid Comm Mass Spectrometry

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“…The formation of radical cations for aromatic amines has been discussed in our previous article. [14] On the basis of the results shown above, it appears that among the various types of amino groups, only the primary and secondary aliphatic amines could undergo DCTB adduction in MALDI, with the primary amine showing much stronger tendency to undergo such adduction. The reason for these will be discussed later in this article.…”

Section: Resultsmentioning

confidence: 95%

A pitfall of using 2‐[(2E)‐3‐(4‐tert‐butylphenyl)‐2‐methylprop‐2‐enylidene]malononitrile as a matrix in MALDI TOF MS: chemical adduction of matrix to analyte amino groups

et al. 2010

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2-[(2E)-3-(4-tert-Butylphenyl)-2-methylprop-2-enylidene]malononitrile (DCTB) has been considered as an excellent matrix for matrix-assisted laser desorption/ionization (MALDI) of many types of synthetic compounds. However, it might provide troublesome results for compounds containing aliphatic primary or secondary amino groups. For these compounds, strong extra ion peaks with a mass difference of 184.1 Da were usually observed, which might falsely indicate the presence of some unknown impurities that were not detected by other matrices. On the basis of the possible mechanisms proposed, these extra ions are the products of nucleophilic reactions between analyte amino groups and DCTB molecules or radical cations. In these reactions, an amino group replaces the dicyanomethylene group of DCTB forming a matrix adduct via a -C=N-bond. An aliphatic primary amine could react easily with DCTB and the reaction could start once they are mixed in a MALDI solution. For an aliphatic secondary amine, on the other hand, the reaction most likely occurs in the gas phase. Protonation of amino groups by adding acid seems to be a useful way to stop DCTB adduction for compounds with one single amino group, but not for compounds with multiple amino groups. Unlike aliphatic primary or secondary amines, aliphatic tertiary amines and aromatic amines do not yield DCTB adducts. This is because tertiary amines do not have the required transferrable H-(N) atom to form an extra -C=N-bond, while aromatic amines are not sufficiently nucleophilic to attack DCTB. In view of the possible matrix adduction, care should be taken in MALDI time-of-flight mass spectrometry (TOF MS) when DCTB is used as the matrix for compounds containing amino group(s).

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“…In the positive mode of MALDI TOF MS, a neutral molecule usually attracts only one cation to form a cation adduct, or it loses one electron to from a radical cation. The mechanisms for the formation of these normal types of ions have been discussed thoroughly in the literature 17–21. In contrast, the observation of double cation adduction to a neutral compound is quite unusual.…”

Section: Introductionmentioning

confidence: 99%

Double cation adduction in matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of electron deficient anthraquinone derivatives

et al. 2007

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Six anthraquinone derivatives were analyzed using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI TOF MS). Clear (pseudo) molecular ions were observed for all the compounds. Interestingly, for some derivatives, strong ions with double cation adduction were also recorded in the positive mode. It is remarkable that all these ions are singly charged. In this work, possible mechanisms for the double cation adduction were investigated and discussed. It appears that the double cation adduction was due to the electron deficient nature of the derivatives, and formed by taking up two singly charged cations and one electron. Substituents on the anthraquinone ring were found to have a significant effect on the double cation adduction. In contrast, no considerable influence of the acidity of MALDI matrix/solution was observed, even on the double proton adduction. Furthermore, it was demonstrated that double cation adduction might occur in the MALDI gas-phase plume. In addition to the anthraquinones, three more electron deficient compounds of different types, i.e. a perylene bisimide derivative (PB), 3,7-decanoylamino-4,8-dihydrobenzo[1,2-b:4,5-b']dithiophene-4,8-dione (TQ) and 6,6-phenyl C61-butyric acid methyl ester (PCBM), were also analyzed with MALDI TOF MS. The results indicate that the 'abnormal' double cation adduction might be a 'normal' phenomenon in the MALDI TOF MS analysis of many electron deficient compounds.

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Radical cation formation in characterization of novel C₃‐symmetric disks and their precursors by matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry

Cited by 9 publications

References 43 publications

Titanium dioxide anatase as matrix for matrix‐assisted laser desorption/ionization analysis of small molecules

Titanium dioxide anatase as matrix for matrix‐assisted laser desorption/ionization analysis of small molecules

A pitfall of using 2‐[(2E)‐3‐(4‐tert‐butylphenyl)‐2‐methylprop‐2‐enylidene]malononitrile as a matrix in MALDI TOF MS: chemical adduction of matrix to analyte amino groups

Double cation adduction in matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry of electron deficient anthraquinone derivatives

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