Direct infusion Mass Spectrometry

Instrument: Thermo Exactive Plus Orbitrap mass spectrometer / Thermo TSQ Endura triple quadrupole mass spectrometer

Perhaps the simplest form of mass spectrometry involves pumping the sample to be analysed directly into the mass spectrometer in a process termed direct infusion mass spectrometry. Typically, the liquid sample is contained in a syringe and a syringe pump is used to deliver a regular flow of liquid.

Direct infusion is suitable for use with samples that are pure or that are simple mixtures composed of only a small number of constituents. Crucially, the sample must also be free of contaminating factors that might interfere with mass spectrometric measurements, such as high levels of non-volatile salts/buffers and detergents.

Direct infusion is compatible with mass spectrometers equipped with electrospray ionisation, and we can acquire either intact molecular masses of analytes, or fragment them and measure the mass of the fragments to allow 'fingerprinting' of chemicals that aid identification.

Typical uses of direct infusion mass spectrometry are for confirmation of the identity of small chemicals and biomolecules, for measuring the mass of small proteins or for analysing macromolecular complexes, which can be preserved when analysed by the mass spectrometer in this way.
Technical Detail
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Sample requirements