Infrared pulsed fiber laser-produced silver-109 nanoparticles for laser desorption/ionization mass spectrometry of 3-hydroxycarboxylic acids.

Abstract

3-Hydroxycarboxylic acids are one of the major components of bacterial lipopolysaccharides (LPS), also known as endotoxins. Endotoxins pose a serious health risk and can seriously damage the internal organs of humans and animals. 3-Hydroxycarboxylic acids can be used as environmental markers to determine endotoxin levels. At the time of preparation of this manuscript no studies on laser mass spectrometry (MS) and analysis with silver nanoparticles (NP) for 3-hydroxycarboxylic acids have been published in literature. Six acids, 3-hydroxyoctanoic (3-OH-C8:0), 3-hydroxydecanoic (3-OH-C10:0), 3-hydroxydodecanoic (3-OH-C12:0), 3-hydroxytetradecanoic (3-OH-C14:0), 3-hydroxyhexadecanoic (3-OH-C16:0), and 3-hydroxyoctadecanoic (3-OH-C18:0) acids, were used as test compounds on the target containing silver-109 NPs for quantification using matrix-assisted laser desorption/ionization (MALDI)-type mass spectrometer. Methods were also tested on spiked human blood serum samples to quantify 3-hydroxycarboxylic acids and verify the influence of the biological matrix on the measurement. Analyzed acids were directly tested in 1000 000-fold concentration change conditions ranging from 1mg/mL to 1ng/mL. The semi-automatic MSI (MS imaging) method allowed us to obtain two to five times lower limit of detection (LOD) and lower limit of quantitation (LLOQ) values than common LDI (Bruker Daltonics, Bremen, Germany) method for analyzed acids. For almost all results of 3-hydroxycarboxylic acids, the trendline fit was better for the semi-automatic MSI method than the manual LDI method. For the first time, the use of laser MS for the quantification of 3-hydroxycarboxylic acids has been demonstrated, and it has been proven that it can be used in the quantitative analysis of such compounds over a wide range of concentrations. In addition, a comparison of two methods-manual LDI-MS and semi-automatic MSI-is presented.