Matrix effects on selectivities of poly(ethylene glycol)s for alkali metal ion complexation in matrix-assisted laser desorption/ionization

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.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Chinthaka¹,

Rodgers²

2012

“…In recent years many factors influencing the quality of MALDI mass spectra of synthetic polymers were investigated especially factors of sample preparation. It has been shown that the matrix type, cationization reagent, their concentrations, as well as the type of solvent or solvent mixture, and the spotting technique affect the polymer distribution [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Besides sample preparation, the instrumentation parameters influence the determined molar mass distribution [17,18].…”

mentioning

confidence: 99%

Investigating the effect of mixing ratio on molar mass distributions of synthetic polymers determined by MALDI-TOF mass spectrometry using design of experiments

Brandt¹,

Ehmann²,

Otto

2010

It is well known that the mixing ratio affects the molar mass distribution of synthetic polymers determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Surely, the molar mixing ratio determines whether a mass spectrum will be obtained or not. However, depending on the mass range, several effects such as multimer formation occur, which might be a source of errors in molar mass distribution calculations. In this study, the effect of mixing ratio was investigated for several synthetic polymers, including polystyrene (PS), poly(dimethylsiloxane) (PDMS), poly(ethylene glycol) (PEG), and poly (methyl methacrylate) (PMMA) using statistical designs of experiments. The 2 3 full factorial design was found to be suitable in the study of more than 1000 samples. The obtained MALDI mass spectra as well as the ANOVA statistics show that the mixing ratio affects the molar mass distribution. The optimal mixing ratio for a defined synthetic polymer depends on the studied combination (matrix, cationization reagent, solvent). (J Am Soc Mass Spectrom 2010, 21, 1870 -1875

“…This is more pronounced as the polarity of the polymers decreases. For example, mass spectrometric analysis of polar polymers such as polyethylene glycol (PEG) and polypropylene glycol (PPG) can easily be achieved using MALDI and/or ESI [3][4][5][6][7][8][9][10]. Nonpolar polymers such as polystyrenes are also amenable to MALDI and ESI through the formation of silver-or copper-cationized adduct ions [11][12][13][14].…”

mentioning

confidence: 99%

Atmospheric pressure photoionization mass spectrometry of polyisobutylene derivatives

Kéki

Török

Nagy

et al. 2008

Atmospheric pressure photoionization mass spectrometric (APPI-MS) study on three types of polyisobutylene derivatives is reported. Two of the polyisobutylenes investigated were polyisobutylene with dihydroxy and diolefinic end-groups derived from aromatic moieties [dicumyl chloride, 1,4-bis(2-chloro-2-propyl)benzene], and the third contained no aromatic moieties with a monohydroxy end-group. All three polyisobutylene derivatives (PIBs) had an average molecular weight (M n ) of ϳ2000 g/mol, with a polydispersity lower than 1.2. In the positive ion APPI mode, protonated PIB molecules were formed, but the molecular weights obtained were considerably lower than those expected, indicating fragmentation of the PIB chains. In the negative APPI mode, using solvents such as tetrahydrofuran and toluene as dopants, no signal was obtained. However, in chlorinated solvents, such as CCl 4 , CHCl 3 , and CH 2 Cl 2 , in the presence of toluene dopant, PIB adducts with chloride ions were formed with relatively high signal intensity. In the case of CH 2 Cl 2 , no dopant (toluene) was necessary to generate chlorinated adduct ions, albeit increasing the toluene concentration in the flow increased the PIB signal intensity. The effect of the toluene concentration on PIB signal intensity was studied and models that include (1) photoionization of toluene, (2) formation of chloride ions from the chlorinated solvents by dissociative electron capture, (3) formation of chlorinated adduct ions and charge recombination reactions between the toluene radical cation, (4) chloride ions, and (5) olymer characterization, including the determination of molar mass, molar mass distribution, the mass of the repeat unit and end-groups, and functionality, is an important process that can be accomplished using several methods. Mass spectrometric methods, particularly those that utilize soft-ionization techniques, e.g., matrix-assisted laser desorption/ionization (MALDI) [1,2] or electrospray ionization (ESI) [3], are superior to other methods because they offer a unique capability to determine all of these parameters. Contrary to other spectroscopic methods, such as nuclear magnetic resonance (NMR), which can only determine an average value of some of the above parameters [e.g., the number-average molecular weight (M n ) and number average-functionality (F n )], mass spectrometric methods provide not only these average values, but the individual intact polymer molecules can also be detected. However, because soft-ionization is based on forming adduct ions with metal ions, e.g., alkali or silver ions or through protonation and/or deprotonation, mass spectrometric analysis of polymers having moieties that are unable to form ions presents difficulties. This is more pronounced as the polarity of the polymers decreases. For example, mass spectrometric analysis of polar polymers such as polyethylene glycol (PEG) and polypropylene glycol (PPG) can easily be achieved using . Nonpolar polymers such as polystyrenes are also amenable to MALDI and ESI through the f...