Abstract

Preparation of monoisotopic silver-109 nanoparticles (109AgNPs) by pulsed fiber laser (PFL) ablation synthesis in solution (LASiS) with the use of a 2D galvoscanner (2D GS) is described. The procedure of covering of custom-made stainless-steel MALDI targets containing studied objects via nebulization is also presented. Examples of application of the new method (PFL-2D GS LASiS and nebulization) in mass spectrometry (MS) analyses and MS imaging (MSI) are shown. These include tests with a nonionic nucleoside and saccharide, ionic amino acids, and also a low-molecular-weight polymer. Fingerprint MS imaging is shown as an example of a fast and simple MSI procedure.

Highlights

  • One of the most utilized laser mass spectrometry methods is matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS), which was developed by Tanaka et al in 1988.1 It offers soft ionization potential, being a powerful analytical tool for the analysis of ionic high-molecular-weight molecules, such as peptides, proteins, and DNA/RNA,[2−4] and, it is useful for detection of some nonionic classes of chemical compounds such as lipids, etc.[5−7] MALDI has not been too often applied to detect low-molecular-weight (LMW) compounds (MW < 1000 Da), because MALDI matrices are low-molecular-weight organic acids and produce a variety of matrix-related ions during the desorption/ionization process, which complicates the spectrum and causes suppression of analyte peaks.[8−10]

  • The laser mass spectrometry usually is realized via MALDI methodology

  • Preparation of silver nanoparticles by a chemical reduction method for laser mass spectrometry was presented by Hua and co-workers

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Summary

■ INTRODUCTION

One of the most utilized laser mass spectrometry methods is matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS), which was developed by Tanaka et al in 1988.1 It offers soft ionization potential, being a powerful analytical tool for the analysis of ionic high-molecular-weight molecules, such as peptides, proteins, and DNA/RNA,[2−4] and, it is useful for detection of some nonionic classes of chemical compounds such as lipids, etc.[5−7] MALDI has not been too often applied to detect low-molecular-weight (LMW) compounds (MW < 1000 Da), because MALDI matrices are low-molecular-weight organic acids and produce a variety of matrix-related ions during the desorption/ionization process, which complicates the spectrum and causes suppression of analyte peaks.[8−10]. The GS module allowed us to use a 20 W pulsed fiber laser directly on the ablation target with a full laser frequency of 80 kHz. Generated silver-109 nanoparticles are shown to be highly useful for LDI mass spectrometry and mass spectrometry imaging (MSI). LDI-ToF mass spectrometry experiments were performed using a Bruker Autoflex Speed ToF mass spectrometer equipped with a SmartBeam II laser (355 nm). A 0.5 μL volume of each of the final solutions was applied to the steel target and air-dried followed by nebulization with the 109AgNP suspension. A volume of 1 μL of sample mixed with matrix solution was placed directly on steel plate and air-dried, and the target was inserted into an MS apparatus for measurement. Preparation of the ungroomed fingerprint for mass spectrometry imaging was obtained by touching the clean steel target for approximately 1 s.

■ RESULTS AND DISCUSSION
■ CONCLUSIONS
■ REFERENCES
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