ESI

ESI source coupled with a quadrupolar mass spectrometer

Paola Bolognesi  -

Jacopo Chiarinelli  -

 

Mass Spectrometry Laboratory

 

 

Overview of the electrospray set-up. 

From the entrance capillary the ions travel through a skimmer, an octupole ion guide, a quadrupole mass filter (visible in the scheme) and a quadrupolar deflector.

The ESI source operates at ambient pressure and the produced molecular ions are transported in vacuum via a differential pumping section. A system of electrostatic lenses and an octupole remove most of the contaminations from neutral species and solvent molecules, transporting the ion beam into a quadrupole mass filter (QMS), operated in high vacuum, which performs the mass/charge selection. An electrostatic deflector then directs the beam either to a characterization section or to a “soft-landing” deposition chamber. A third line for gas phase spectroscopy will be implemented in the near future.
 
 

TECHNICAL SPECIFICATIONS

The ESI technique requires small concentrations (10-5 M) of the analyte in mixed solution of water and organic solvents.

  • Mass spectrometry.
    The quadrupole mass filter (QMS Extrel 2cm rods – 440 KHz radiofrequency) covers the m/z range 4-4000 and can be used as a mass filter (m/z analysis) or in total transmission.
  • “Soft lading”.
    A deposition chamber is available, with fast entry of the sample and diagnostic tools for the optimization of the deposition conditions. Any conductive material can be used as substrate.

AVAILABLE TECHNIQUES

The apparatus is currently under installation and commissioning.

  • Mass spectrometry analysis of different types of compounds an complexes.
  • “Soft-Landing” deposition of m/z selected species on conductive substrates and in high vacuum conditions, with control of the kinetic energy of the ions that can be performed after m/z selection.
 

SAMPLE

The technique is available for molecules and compounds in the mass range between few Da and several tens of kDa. Sample has to be soluble in a mixed solution of water and organic solvent (ethanol, methanol or acetonitrile in typical percentage of 50-20%).

Typical samples are:

  • Small biomolecule (i.e. peptides, nucleobases)

  • Large biomolecules (i.e. proteins and enzymes, DNA strands)

  • Nanoparticles

  • Short polymers and biopolymers

Different samples can also be considered and tested for feasibility.

USE FOR

  • Spectrometric analysis of unknown compounds for insights into their composition.
  • Analysis of complexes formed in liquid solution and their selective binding properties.
  • Deposition under clean conditions (high vacuum) of fragile compounds for conformational characterization. 

  • Deposition under clean conditions for device fabrication, with or without m/z selection.
 
 
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