Köln 2025 – scientific programme

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MS: Fachverband Massenspektrometrie

MS 7: New Methods, Technical Development II

MS 7.1: Talk

Thursday, March 13, 2025, 14:45–15:00, HS 2 Chemie

Optimizing ToF-SIMS Analysis Conditions for Detecting Antibiotics in Frozen Hydrated Samples — •Michael Bäumer, Thorsten Adolphs, Richard Erling Peterson, Bonnie June Tyler, and Heinrich Franz Arlinghaus — University of Münster, Münster, Germany

In order for most biological specimens to be analyzed with ToF-SIMS, either the water must be removed via a process such as freeze-drying or the samples must be frozen and analyzed under cryogenic conditions. Cryogenic preparation and analysis of biological samples preserves the 3-dimensional structure of tissues and biofilms and can prevent migration artifacts that occur during freeze-drying. However, ToF-SIMS analysis of frozen aqueous sample systems results in a spectrum of pure and non-pure water ice cluster ions, extending to high masses, which can interfere with detection of biomolecules. Furthermore, metastable decay of the cluster ions in the time-of-flight analyzer can lead to a high background that raises the detection limit for target analytes. In this study, we have investigated the influence of a range of analytical parameters, including primary ion species, cluster size, analysis temperature and analyzer voltages, on the spectrum of water ice mixed with typical biological sample preparation additives such as dextran, ammonium formate, acetic acid and the antibiotic ciprofloxacin. The aim of this work is to optimize analysis conditions in order to improve the detection limit for antibiotic compounds. We also provide an outlook on further reduction of background signals by the destruction of water ice clusters using a 157 nm excimer laser.

Keywords: Frozen Hydrated; Metastable; Temperature; Primary Ion; Laser Post Ionization