Attachment of Chloride Anion to Sugars: Mechanistic Investigation and Discovery of a New Dopant for Efficient Sugar Ionization/Detection in Mass Spectrometers

Abstract

A new method for efficient ionization of sugars in the negative-ion mode of electrospray mass spectrometry is presented. Instead of using strongly hydrophobic dopants such as dichloromethane or chloroform, efficient ionization of sugars has been achieved by using aqueous HCl solution for the first time. This methodology makes it possible to use hydrophilic dopants, which are more appropriate for chromatographic separation techniques with efficient sugar ionization and detection in mass spectrometry. The interaction between chloride anions and monosaccharides (glucose and galactose) was studied by DFT in the gas phase and by implementing the polarizable continuum model (PCM) for calculations in solution at the high B3LYP/6-31+G(d,p)//B3LYP/6-311+G(2d,p) level of theory. In all optimized geometries of identified [M+Cl](-) anions, a non-covalent interaction exists. Differences were revealed between monodentate and bidentate complex anions, with the latter having noticeably higher binding energies. The calculated affinity of glucose and galactose toward the chloride anion in the gas phase and their chloride anion binding energies in solution are in excellent agreement with glucose and galactose [M+Cl](-) experimental intensity profiles that are represented as a function of the chloride ion concentration. Density functional calculations of gas-phase affinities toward chloride anion were also performed for the studied disaccharides sucrose and gentiobiose. All calculations are in excellent agreement with the experimental data. An example is introduced wherein HCl was used to effectively ionize sugars and form chlorinated adduct anions to detect sugars and glycosylated metabolites (anthocyanins) in real biological systems (Vitis vinifera grape extracts and wines), whereas they would not have been easily detectable under standard infusion electrospray mass spectrometry conditions as deprotonated species.

Changes in Dissolved Organic Matter during the Treatment Processes of a Drinking Water Plant in Sweden and Formation of Previously Unknown Disinfection Byproducts

“…Chloride ions are problematic, because even at relatively low concentrations, DOM may form chloride adducts that could be mistaken for covalently bound DBPs and were even used as a dopant to analyze saccharides. 28 No chloride adducts were formed in samples collected prior to disinfection in this study, confirming the effectiveness using formic acid instead of HCl to avoid adduct formation. The SPE cartridge was activated using methanol [Sigma-Aldrich Chromasolv liquid chromatography− mass spectrometry (LC-MS) grade methanol], washed with acidified (pH 2) high-purity water (Sigma-Aldrich Chromasolv LC-MS grade water).…”

New particle formation above a simulated salt lake in aerosol chamber experiments

“…The SolariX Fourier-transform ion cyclotron resonance mass spectrometer (FT-ICR/MS; Bruker, Bremen, Germany) was operated with a 12-T superconducting magnet and an Apollo II electrospray source in negative mode. [36] Because there were high salt concentrations in the sample, chlorine adducts [37] and organohalogens could not be clearly distinguished if the SOA sample was dissolved in methanol and directly injected into the ultrahigh-resolution mass spectrometer. Additionally, high saltcluster concentrations would suppress some signals resulting from CHNOS compounds in the spectra.…”

Atmospheric pressure ionization of chlorinated ethanes in ion mobility spectrometry and mass spectrometry

“…The calculations underestimate the binding energy by 2.49 kcal/mol for methylene chloride and 0.79 kcal/mol for chloroform. Although not a direct comparison, chloride adducts with sugars have been calculated [19]. Using the binding energies from the most favorable position on each sugar examined, the binding energy varies from 30.7 to 33.0 kcal/mol.…”