Infrared pulsed fiber laser-produced silver-109-nanoparticles for laser desorption/ionization mass spectrometry of amino acids.

Application of monoisotopic cationic 109 Ag nanoparticles ( 109 AgNPs) obtained by pulsed fiber laser (PFL) 2D galvo-scanner (GS) laser generated nanomaterial (LGN) for both high resolution laser desorption/ionization mass spectrometry and mass spectrometry imaging of amino acids is presented. Four amino acids, alanine, isoleucine, lysine, and phenylalanine were used as test compounds for quantification with matrix-assisted laser desorption/ionization mas (MALDI)-type mass spectrometer. Comparison of commonly made manual measurements with semiautomatic mass spectrometry imaging (MSI) was performed providing very interesting findings. Amino acids were directly tested in 1 000 000-fold concentration change conditions ranging from 1 mg/ml to 1 ng/ml, which equates to 500 ng to 500 fg of amino acid per measurement spot. Methods were also tested on samples of human blood plasma for quantification of endogenous amino acids.