Enhanced Cationization of Polymers Using Delayed Ion Extraction with Matrix-assisted Laser Desorption/Ionization

The traditional solvent-based matrix-assisted laser desorption ionization (MALDI) preparation method has been used to analyze nonpolar polymers of various molecular weights. High resolution silver cationized oligomers with masses of up to 12 KDa were measured using 9.4 tesla Fourier transform mass spectrometry (FTMS) with an external ionization source. It was observed that when time-of-flight mass spectrometry was used, the spectra of polyethylene polymers showed abundant low mass fragment ions. However, these fragments were absent from the FTMS spectra. (J Am Soc Mass

Section: Resultsmentioning

confidence: 99%

Hydrocarbon polymer analysis by external MALDI fourier transform and reflectron time of flight mass spectrometry

Jaber

Wilkins

2005

“…Experiments with other salt layers gave similar results. Detailed MALDI investigations into the cationization of biological samples [32] and polymers [33] have provided ample evidence for metal complexation to occur predominantly in the gas phase, rather than reflecting the desorption of preformed ions from the solid. In recent MALDI experiments it has been possible to distinguish gas phase complexation and ion preformation for cationized crown ethers [34].…”

Section: Laser Fluence Dependency Of Ion Formationmentioning

confidence: 99%

Alkali cation attachment to derivatized fullerenes studied by matrix-assisted laser desorption/ionization

Fati

Leeman

Vasil’ev

et al. 2002

The complexation of alkali metal ions with amphiphilic fullerene derivatives has been investigated by matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry. The formation of analyte ions occurs via two competing mechanisms including electron transfer from matrix-derived ions and metal ion attachment. The interplay of these processes has been examined by laser fluence dependent sample activation and by variation of the target composition. The attachment of metal ions has been established as the gentler and thus more efficient route towards the formation of intact analyte ions. Investigations into the metal ion complexation have been conducted to reveal the reactivity order of the alkali metals in these reactions and to elucidate the influence of structural differences of the analytes, as well as to unravel effects caused by the anionic counter ion of the metal. The experimental data have been derived by two complementary approaches. Competing reactants were either studied simultaneously, so that the product distribution would provide direct insight into the reactivity pattern, and/or product distributions were obtained in a large variety of separate experiments and normalized for reliable comparison. It has been found that the extent to which complexation is observed follows the charge density order of the alkali metal ions. The structural features of the fullerene-attached ligands were of profound influence on the attachment of the metal ion, inducing enhanced selectivity for the complexation with less reactive metals. The metal ion attachment is reduced with the use of smaller anionic counter ions. Rationalization of these findings is provided within the framework of the mechanisms of ion formation in

“…MALDI is also widely used for the analysis of syntactic polymers [1][2][3][4][5][6][7][8][9][10][11][12] and has also been successfully employed for the analyses of other macromolecules such as fullerenes [13], carbon nanotubes [14], and dendrimers [15][16][17]. Because a large number of experimental parameters influence the ionization processes that occur in MALDI, the ionization mechanisms and kinetics are not fully understood despite its widespread usage and popularity.…”

Section: Introductionmentioning

confidence: 99%

Sodium Cation Affinities of Commonly Used MALDI Matrices Determined by Guided Ion Beam Tandem Mass Spectrometry

Chinthaka¹,

Rodgers²

2012

The sodium cation affinities of six commonly used MALDI matrices are determined here using guided ion beam tandem mass spectrometry techniques. The collision-induced dissociation behavior of six sodium cationized MALDI matrices, Na + (MALDI), with Xe is studied as a function of kinetic energy. The MALDI matrices examined here include: nicotinic acid, quinoline, 3-aminoquinoline, 4-nitroaniline, picolinic acid, and 3-hydroxypicolinic acid. In all cases, the primary dissociation pathway corresponds to endothermic loss of the intact MALDI matrix. The cross section thresholds are interpreted to yield zero and 298 K Na + −MALDI bond dissociation energies (BDEs), or sodium cation affinities, after accounting for the effects of multiple ionneutral collisions, the kinetic and internal energy distributions of the reactants, and dissociation lifetimes. Density functional theory calculations at the B3LYP/6-311+G(2d,2p)//B3LYP/6-31G* and MP2(full)/6-311+G(2d,2p)//B3LYP/6-31G* levels of theory are used to characterized the structures and energetics for these systems. The calculated BDEs exhibit very good agreement with the measured values for most systems. The experimental and theoretical Na + −MALDI BDEs determined here are compared with those previously measured by cation transfer equilibrium methods.