Effects of molecular weight and cationization agent on the sensitivity of Bi cluster secondary ion mass spectrometry.

RATIONALE Bi cluster secondary ion mass spectrometry (SIMS) is one of the most promising tools for precise analysis of synthetic polymers. However, the sensitivity in the high-mass region is still insufficient compared with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS). Accordingly, the effects of metal assistance (cationization agents) were investigated in this study. METHODS To investigate the effects caused by varying the ionization agent, three different polyethylene glycol (PEG) samples were prepared, one with an Ag-deposited film, and two others mixed with Ag and Na, respectively. The measurements were performed by using a commercial Bi cluster SIMS and MALDI-TOFMS systems. The mass spectrum obtained with MALDI-TOFMS was used as a reference molecular weight distribution to evaluate the effects of molecular weight and primary ion species (Bi+ , Bi3+ , Bi32+ ) on the sensitivity of Bi cluster SIMS. RESULTS The intensity of each secondary ion was the highest in Bi32+ irradiation, and the lowest in Bi+ irradiation. Regarding the cationization agents, the secondary ion yield was the highest for the sample mixed with Ag, while the degree of decay of sensitivity along with the increase in molecular weight was the smallest for the sample mixed with Na. CONCLUSIONS It was suggested that the cationization mechanism consists of pre-formed ionization and gas-phase ionization processes. The sensitivity of Bi cluster SIMS decreases to approximately one-fiftieth in every 1000 u. These results might help in understanding the mechanism of cationization and further enhancement of secondary ion yields of polymers. Copyright © 2016 John Wiley & Sons, Ltd.

[1]  V. Cristaudo,et al.  Sputtering of polymers by keV clusters: Microscopic views of the molecular dynamics , 2014 .

[2]  J. Vitz,et al.  Mass spectrometric imaging of synthetic polymers. , 2014, Analytica chimica acta.

[3]  C. Werner,et al.  Characterization of polymer membranes by MALDI mass-spectrometric imaging techniques. , 2013, Analytical chemistry.

[4]  Christine M Mahoney,et al.  Cluster secondary ion mass spectrometry of polymers and related materials. , 2010, Mass spectrometry reviews.

[5]  H. Arlinghaus,et al.  Effects of metal nanoparticles on the secondary ion yields of a model alkane molecule upon atomic and polyatomic projectiles in secondary ion mass spectrometry. , 2008, Analytical chemistry.

[6]  Jun Tamura,et al.  Development of a high-Performance MALDI-TOF mass spectrometer utilizing a spiral ion trajectory , 2007, Journal of the American Society for Mass Spectrometry.

[7]  A. Wucher.  Molecular secondary ion formation under cluster bombardment: A fundamental review , 2006 .

[8]  David Touboul,et al.  Improvement of biological time-of-flight-secondary ion mass spectrometry imaging with a bismuth cluster ion source , 2005, Journal of the American Society for Mass Spectrometry.

[9]  N. Winograd.  The Magic of Cluster SIMS , 2005 .

[10]  F. Kollmer.  Cluster primary ion bombardment of organic materials , 2004 .

[11]  P. Bertrand,et al.  Organic secondary ion mass spectrometry: sensitivity enhancement by gold deposition. , 2002, Analytical chemistry.

[12]  B. Guo,et al.  Investigation of metal attachment to polystyrenes in matrix-assisted laser desorption ionization , 1998 .

[13]  R. Caprioli,et al.  Molecular imaging of biological samples: localization of peptides and proteins using MALDI-TOF MS. , 1997, Analytical chemistry.

[14]  Liang Li,et al.  Mass Discrimination in the Analysis of Polydisperse Polymers by MALDI Time-of-Flight Mass Spectrometry. 1. Sample Preparation and Desorption/Ionization Issues , 1997 .

[15]  Renato Zenobi,et al.  Ionization mechanisms in matrix-assisted laser desorption/ionization mass spectrometry: contribution of pre-formed ions , 1997 .

[16]  David M. Hercules,et al.  Molecular weight distributions of polymers using time-of-flight secondary-ion mass spectrometry , 1991 .

[17]  K. Ichiki,et al.  The effect of incident energy on molecular depth profiling of polymers with large Ar cluster ion beams , 2011 .