Nanospray desorption electrospray ionization (nano-DESI) is an ambient pressure ionization technique used in mass spectrometry (MS) for chemical analysis of organic molecules. In this technique,

analyte An analyte, component (in clinical chemistry), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The purest substances are referred to as analytes, such as 24 karat gold, NaCl, water, etc. ...

s are

desorbed Desorption is the physical process where a previously adsorbed substance is released from a surface. This happens when a molecule gains enough energy to overcome the activation barrier of the bounding energy that keeps it in the surface. There ...

into a liquid bridge formed between two capillaries and the sampling surface. Unlike desorption electrospray ionization (DESI), from which nano-DESI is derived, nano-DESI makes use of a secondary capillary, which improves the sampling efficiency.

Principle of operation

The typical nano-DESI probe setup consists of two

fused silica Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non- crystalline) form. This differs from all other commercial glasses in which other ingredients are added which ch ...

capillaries - primary capillary which supplies

solvent A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...

and maintains a liquid bridge, and secondary capillary which transports the dissolved analyte to the mass spectrometer. High

voltage Voltage, also known as electric pressure, electric tension, or (electric) potential difference, is the difference in electric potential between two points. In a static electric field, it corresponds to the work needed per unit of charge to ...

(several kV) is applied between the inlet of the mass spectrometer and the primary capillary, creating a self-aspirating nanospray. The liquid bridge is maintained by continuous flow of the solvent and the contact area between the solvent bridge and sample surface can be controlled by changing the solvent flow rate, varying the diameter of the utilized capillaries and regulating the distance between the sample and the nano-DESI probe. In this way, the

spatial resolution In physics and geosciences, the term spatial resolution refers to distance between independent measurements, or the physical dimension that represents a pixel of the image. While in some instruments, like cameras and telescopes, spatial resolut ...

mass spectrometry imaging Mass spectrometry imaging (MSI) is a technique used in mass spectrometry to visualize the spatial distribution of molecules, as biomarkers, metabolites, peptides or proteins by their molecular masses. After collecting a mass spectrum at one spot, ...

applications can be improved, with typical resolution ranging between 100 - 150 μm.

Applications

Nano-DESI has been applied for localized analysis of complex molecules and imaging of tissue sections,

microbial communities Microbial population biology is the application of the principles of population biology to microorganisms. Distinguishing from other biological disciplines Microbial population biology, in practice, is the application of population ecology and popu ...

and environmental samples.

References

{{Reflist Mass spectrometry Spatial analysis