Lateral resolution of desorption nanoelectrospray: a nanospray tip without nebulizing gas as a source of primary charged droplets

Abstract

Desorption nanoelectrospray (nanoDESI) was described in 2007 and it represents a miniaturized version of desorption electrospray without the assistance of the nebulizing gas. Compared to DESI, a nanoelectrospray tip (2 ± 1 μm I.D.) generates primary charged droplets of smaller sizes and lower spray liquid flow rates. This is the first report on utilization of nanoDESI for mass spectrometry imaging (MSI). Its new coupling with a Q-TOF instrument allowed faster mass spectra acquisition (4 Hz) essential for MSI of fine surface details. To evaluate nanoDESI potential for mass spectrometry imaging, etched glass substrates with Rhodamine B patterns of different dimensions were prepared. The Rhodamine B lines were analysed in 1D scanning mode and their width was determined experimentally by nanoDESI measurement. The experimental data revealed that the lateral resolution of nanoDESI is close to 30 μm along the x-axis (orthogonal to the inlet). 2D scanning mode confirmed good resolution along both axes as dye squares with dimensions about 60 μm × 60 μm were easily distinguished. The low flow rate of the spray liquid reduced undesirable analyte washing effects, which allowed repeated scanning analysis of the surface. The presented results demonstrate the applicability of nanoDESI for high surface resolution mass spectrometry imaging.

Ion Source with Laser Triangulation for Ambient Mass Spectrometry of Nonplanar Samples

“…In this work, the sample stage moved with a minimum step size of 100 μm, which was sufficient taking into account the spot size achievable with the sprayers used. However, a stage movable in shorter steps can easily be constructed for sprayers offering better lateral resolution such as nanoDESI . Lateral resolution achievable with desorption spray-based techniques is inherently limited when compared to laser-based approaches such as LAESI or sampling probe on the robotic arm for mechanical desorption (ROPPI-MS) .…”

Structural Analysis of Natural Products

“…Those tools, especially when mutually combined, may provide natural product chemists new standardized protocols. In the MSI field, nanoDESI imaging with 30 μm lateral resolution or application of innovative laser optics and mechanical improvements for high data collection speed in MALDI tissue imaging might compete with optical microscopy tools…”

“…Those tools, especially when mutually combined, may provide natural product chemists new standardized protocols. In the MSI field, nanoDESI imaging with 30 μm lateral resolution 97 or application of innovative laser optics and mechanical improvements for high data collection speed in MALDI tissue imaging might compete with optical microscopy tools. 98 The sizes of superconducting magnets for NMR spectroscopy and FTICR mass spectrometry are being minimized to better fit into the laboratory frame without loss of magnetic field strength.…”

Signal enhancement in desorption nanoelectrospray ionization by custom‐made inlet with pressure regulation

“…Promising very good resolution of dye squares (60 μm × 60 μm) has been achieved 8 . Although technical development has improved the robustness of nanoDESI 5 and a modification of inlet has allowed its implementation on a Q‐TOF mass spectrometer, 8 sensitivity of measurement can still be an issue. Because a very small surface area is sampled, only a tiny amount of analyte is available for desorption and ionization.…”

“…Considering imaging applications, the low flow rate of spraying liquid decreases sample washing off which can be advantageous for lateral resolution and can enable repeat scans of the same surface area. Promising very good resolution of dye squares (60 μm × 60 μm) has been achieved 8 . Although technical development has improved the robustness of nanoDESI 5 and a modification of inlet has allowed its implementation on a Q‐TOF mass spectrometer, 8 sensitivity of measurement can still be an issue.…”