Gas aggregated Ag NPs as a matrix for small molecules: a study on natural amino acids
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RESEARCH PAPER
Gas aggregated Ag NPs as a matrix for small molecules: a study on natural amino acids Vadym Prysiazhnyi & Filip Dycka Kratochvil & Vitezslav Stranak
&
Jiri
Received: 18 June 2020 / Accepted: 6 November 2020 # Springer Nature B.V. 2020
Abstract The use of nanomaterials as a matrix for soft ionization mass spectrometry has been investigated and reported various times. Under certain conditions, measurements of samples containing small molecules enhanced by nanomaterials have better sensitivity compared with other methods. Nanoscaled Ag prepared by various methods was reported as a substrate for surface-assisted LDI MS. Higher desorption and (in some cases) charge transfer through adduct formation with silver ion was reported. But primary ionization mechanism was through attachment of proton or alkali ion. Our approach is to overcoat the sample by Ag nanoparticles (the so-called nanoparticle-assisted LDI MS or nanoPALDI MS). As nanoparticles having adsorption maxima close to the laser wavelength, we expect an improvement in desorption enhancement, release of silver ions and (as a result of latter) increased adduct formation of [analyte+Ag]+ ions. The nanoparticles are produced by gas aggregation under lowpressure, making the process homogeneous over relatively large areas, free from impurities, and absence of capping agent often presented in colloidal nanoparticles. This work V. Prysiazhnyi (*) Department of Chemisty, Faculty of Science, Masaryk University, Kamenice 5 (C14), Brno 62500, Czech Republic e-mail: [email protected] V. Prysiazhnyi : F. Dycka : J. Kratochvil : V. Stranak Faculty of Science, University of South Bohemia, Branisovska 1760, 37005 Ceske Budejovice, Czech Republic J. Kratochvil : V. Stranak Institute of Physics of the Czech Academy of Sciences, Na Slovance 2, 18221 Prague, Czech Republic
reports the detection of natural amino acids with Ag nanoparticles as a matrix. We successfully detected all amino acids (as [analyte+Ag]+ ion), including in the mixtures of few amino acids. Moreover, a formation of other adducts, particularly [analyte+Ag3]+ and [analyte2+Ag]+ is reported. The differences in ion intensity ratios depending on amino acid types are discussed. The obtained results showed that laser ablation is more efficient for amino acids with hydrophobic, unique, and neutral side chains. Keywords Amino acids . Ag NPs . Gas aggregation source . Nano-PALDI MS . Nanomaterials
Introduction The detection of small molecules with molar masses below 900 g/mol is required for many applications in medicine (Shanta et al. 2012), biology (Kaspar et al. 2011), forensic (Guinan et al. 2015), and others. To identify them on the surface (and quantify, in some cases), laser desorptionionization mass spectrometry (LDI MS) can be used. It is an advanced analytical technique that can measure a variety of objects ranging from single molecules to structures consisting of millions of atoms (Cohen and Gusev 2002; Schriemer and Li 2002; Goodwin et al. 2008). To increase the method’s sensitivity,
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