Established and emerging atmospheric pressure surface sampling/ionization techniques for mass spectrometry

Abstract

The number and type of atmospheric pressure techniques suitable for sampling analytes from surfaces, forming ions from these analytes, and subsequently transporting these ions into vacuum for interrogation by MS have rapidly expanded over the last several years. Moreover, the literature in this area is complicated by an explosion in acronyms for these techniques, many of which provide no information relating to the chemical or physical processes involved. In this tutorial article, we sort this vast array of techniques into relatively few categories on the basis of the approaches used for surface sampling and ionization. For each technique, we explain, as best known, many of the underlying principles of operation, describe representative applications, and in some cases, discuss needed research or advancements and attempt to forecast their future analytical utility.

What can we learn from ambient ionization techniques?

“…The samples usually maintain their original chemical/physical/biological states without external interference before ionization [1,23]. Biological [24 -27], pharmaceutical [4, 28 -30], environmental [31][32][33][34], food [35][36][37][38], and forensic samples [39 -42] have been successfully examined by ambient mass spectrometry; typical examples of such analyses have been summarized in recent reviews [1,8,43,44]. Although the chemical composition and origins of samples can change dramatically in different studies, solid surfaces, solutions, and liquid mixtures are usually the states to be characterized by ambient mass spectrometry.…”

“…At a recent symposium on Ambient Ionization Mass Spectrometry at Pittcon '09 in Chicago, several speakers declared that there should be "a moratorium on the creation of further acronyms." Cooks and coworkers, in their short reviews on ambient desorption/ionization MS in 2008 and 2009 [1,136], listed 17 different acronyms; Van Berkel's review on atmospheric pressure surface sampling/ionization techniques [8] listed 25 different acronyms! As already stated in the literature [1], some "catchy" acronyms (for example, DART or ASAP) were chosen to be recognized as marketing tools for commercial implementations rather than being descriptive of certain processes occurring.…”

“…However, perhaps fueled by the availability of excellent and very sensitive instrumentation and/or by the fact that the MS field has attracted many brilliant minds, the surge continued and is still continuing. In the last years, there has been a flurry of developments, most notably the introduction of sources for ambient mass spectrometry, including desorption by electrospray ionization (DESI) [2], direct analysis in real time (DART) [3], extractive electrospray ionization (EESI) [4,5], secondary electrospray ionization (SESI) [6,7], and many combinations of desorption with postionization methods working at atmospheric pressure (for a review, see [8]). No less than 25 different ambient surface desorption/postionization methods for the analysis of medium to low volatility compounds have been described in the literature in the last few years!…”

XMS: Cross-Platform Normalization Method for Multimodal Mass Spectrometric Tissue Profiling

“…T he development of mass spectrometric tissue profiling techniques has gained significant momentum within the last two decades [1]. Mass spectrometry imaging (MSI) is rapidly advancing within this field, enabling simultaneous determination of hundreds to thousands of chemical species within a single tissue sample in a spatially resolved manner.…”

Liquid Microjunction Surface Sampling Probe Fluid Dynamics: Characterization and Application of an Analyte Plug Formation Operational Mode

“…Like many other atmospheric pressure surface sampling and ionization approaches coupled with mass spectrometric detection [6][7][8], these probes are conventionally scanned across or brought into contact with surfaces for temporally or spatially-resolved near real-time signal monitoring [9,10]. As a consequence, analyte detection is limited to what is readily extractable from a surface within the timescale of the solvent interaction with the spot of interest.…”