Surface acoustic wave nebulization improves compound selectivity of low-temperature plasma ionization for mass spectrometry

Abstract

Mass spectrometry coupled to low-temperature plasma ionization (LTPI) allows for immediate and easy analysis of compounds from the surface of a sample at ambient conditions. The efficiency of this process, however, strongly depends on the successful desorption of the analyte from the surface to the gas phase. Whilst conventional sample heating can improve analyte desorption, heating is not desirable with respect to the stability of thermally labile analytes. In this study using aromatic amines as model compounds, we demonstrate that (1) surface acoustic wave nebulization (SAWN) can significantly improve compound desorption for LTPI without heating the sample. Furthermore, (2) SAWN-assisted LTPI shows a response enhancement up to a factor of 8 for polar compounds such as aminophenols and phenylenediamines suggesting a paradigm shift in the ionization mechanism. Additional assets of the new technique demonstrated here are (3) a reduced analyte selectivity (the interquartile range of the response decreased by a factor of 7)—a significant benefit in non-targeted analysis of complex samples—and (4) the possibility for automated online monitoring using an autosampler. Finally, (5) the small size of the microfluidic SAWN-chip enables the implementation of the method into miniaturized, mobile LTPI probes.

Benchmarking Cleavable Biotin Tags for Peptide-Centric Chemoproteomics

“…On the other hand, the side chain amines can facilitate peptide protonation/ionization while increasing the charge state of the corresponding peptides . Indeed, Mod 2 and Mod 4 provided a relatively high population of triply charged precursor ions (Figure A).…”

“…On the other hand, the side chain amines can facilitate peptide protonation/ionization while increasing the charge state of the corresponding peptides. 36 Indeed, Mod 2 and Mod 4 provided a relatively high population of triply charged precursor ions (Figure 5A). In contrast, Mod 1 and Mod 3 might trigger the charge-state coalescence phenomenon via charge-state reduction (Figure 5B), thereby favoring the overall gain in MS sensitivity.…”

Faster, better, and cheaper: harnessing microfluidics and mass spectrometry for biotechnology

“…When the samples are atomized, fine particles are produced, a small fraction of which then become charged due to microscopic fluctuations in the initial droplet. Recently, SAWN has been combined with other ambient MS ionization techniques such as atmospheric-Pressure chemical Ionization (APCI) 140 and low-temperature plasma ionization (LTPI) 144 to enhance the sensitivity. Unlike other microfluidic methods for sample manipulation, SAWN chip does not require pressure driven pumps or interconnects, nor the integration of microchannels.…”

Efficient Generation of Plasma‐Activated Aerosols with High Concentrations of Reactive Species via Silicon Dioxide Coated Surface Acoustic Wave Devices

“…[31,32] Various methods have thus been explored in the past to enhance the nebulization rate of SAW nebulizers. Besides changing the SAW frequency, [33] the SAW nebulization rate can also be enhanced through the use of different modulation schemes: 1) pulse-width modulation, i.e., the introduction of on and off cycles to the carrier signal to increase the maximum peak-to-peak voltage; [34,35] 2) amplitude modulation, which alters not only the carrier signal peak-to-peak voltage based on a modulation index but also the modulation frequency; [36,37] ; and 3) hybrid modulation, which is a combination of both the pulse-width and amplitude modulation schemes. [38] When SAW devices were used to nebulize plasma-activated activated water, an approximate 76% increase in the nebulization rate was reported with the use of hybrid modulation as compared to amplitude modulation.…”