@article{dunnavant_eisenberg_muddiman_2025, title={Exploring ammonium salt doping to enhance ion abundance for quantitative mass spectrometry imaging}, DOI={10.1007/s00216-025-06198-z}, abstractNote={Increasing ion abundance in mass spectrometry is essential for enhancing detection, quantification, and understanding of biomolecules involved in key cellular processes. Infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI), MALDI, and nano-DESI have shown improved ion abundance when integrating specific concentrations of ammonium fluoride into the sample preparation and/or ionization steps. Herein, the importance of electronegativity and atomic size for the proposed mechanism of increased ion abundance is evaluated by testing a variety of ammonium halide salts. Ammonium fluoride was confirmed to result in the largest increase in ion abundance and was subsequently used to perform quantitative mass spectrometry imaging (qMSI) of glutathione (GSH) in healthy mouse liver tissue. Using ~70 µM NH<sub>4</sub>F as an ESI dopant, up to a ~ two-fold increase in ion abundance was observed for these biomolecules, as well as an improvement in the limit of detection, detection frequency, and quantification of endogenous GSH in tissue.}, journal={Analytical and Bioanalytical Chemistry}, author={Dunnavant, Alora R. and Eisenberg, Seth M. and Muddiman, David C.}, year={2025}, month={Nov} }
 @article{eisenberg_dunnavant_palomino_muddiman_eisenberg_dunnavant_palomino_muddiman_2025, title={Signal enhancement of lipids and glycans using ammonium fluoride for IR-MALDESI mass spectrometry imaging}, DOI={10.1007/s00216-025-06197-0}, abstractNote={Abstract Mass spectrometry imaging (MSI) is an analytical technique that enables the simultaneous detection and localization of hundreds to thousands of molecules across a tissue surface. The addition of ammonium fluoride to the electrospray or to tissue samples has been shown to increase the signal of lipids in both nano-DESI-MSI and MALDI-MSI, respectively. Herein, this strategy is applied to infrared matrix-assisted laser desorption electrospray ionization (IR-MALDESI) which demonstrated signal enhancement for both lipids and N -linked glycans using 70 µM and 350 µM NH 4 F in 50% ACN with 1 mM acetic acid as the ESI solvent, respectively. Up to a 93-fold increase in signal was observed for these biomolecules without any change in sample preparation or to the mass spectrometer parameters, including detecting lipids not seen with the control ESI solvent. On average, lipids were enhanced by eightfold, and the glycan signal increased by 1.2-fold. The enhancement factor for lipids was significantly impacted by lipid class, while glycan enhancement was affected by charge state and the observed adduct. Graphical Abstract}, journal={Analytical and Bioanalytical Chemistry}, author={Eisenberg, Seth M. and Dunnavant, Alora R. and Palomino, Tana V. and Muddiman, David C. and Eisenberg, Seth M. and Dunnavant, Alora R. and Palomino, Tana V. and Muddiman, David C.}, year={2025}, month={Nov} }