Structured Conductive Probes for Mass Spectrometry

Abstract

The introduction of ionization under ambient conditions has greatly simplified mass spectrometric analysis. Over past decade, ambient ionization mass spectrometry (MS) methods have revolutionized the way complex samples are analyzed under environmental conditions without requiring, in most cases, any sample pretreatment. Ambient ionization MS gained popularity among other analytical techniques due to its simplicity and its suitability for analysis of small and large molecules. However, ambient ionization methods can suffer from low accuracy and sensitivity due to matrix effects and interferences within complex samples, as well as from poor ionization efficiency. Matrix effects in ambient ionization are usually caused by ion suppression and may depend on different factors, e.g. matrix-to-analyte concentration ratios, proton affinities of analyte and matrix species. To overcome these challenges, in this thesis we present a new approach where a probe is used both as a direct sampling device and as an efficient ambient ionization source. This approach leverages high surface area gold electrodes, fabricated through low-cost bench-top fabrication methods and functionalized using self-assembled alkyl thiol monolayers, as functional conductive sampling probes (FCSPs) for the extraction and concentration of analytes from a sample solution. FCSPs loaded with the targeted analytes were then used to demonstrate a new and highly efficient ionization approach, called Primary Ion Mass Spectrometry Source (PIMSS). In this approach, following capture, the bound analytes are directly desorbed into the mass spectrometer, where ionization is achieved solely through the extraction voltage applied to the probe. 3D-printing was used to design an interface to couple FCSPs to the mass spectrometer. In this work, we discuss a detailed method development and optimization stage and present capabilities of the proposed assay.