Mass spectrometry

An analytical technique that ionizes chemical species and separates their ions by mass-to-charge ratio. The resulting spectra reveal the identities and amounts of substances.

Electrospray ionization: An ionization method that creates gas-phase ions from a liquid sample by applying a high voltage. It transfers large, fragile molecules from solution into the instrument with little fragmentation.
Tandem mass spectrometry: A method that selects precursor ions, fragments them, and analyzes the resulting product ions. Fragmentation adds structural evidence and supports selective quantification.
Mass-to-charge ratio: The mass of an ion divided by its integer or effective charge, commonly denoted m/z. Mass analyzers separate ions according to this quantity rather than mass alone.
Nuclear magnetic resonance spectroscopy: A spectroscopy method that uses nuclear magnetic resonance to probe molecular structure and chemical environments. It supplies structural information through magnetic interactions rather than ion mass measurements.
Matrix effect: A change in analytical signal caused by other substances present in a sample matrix. Coexisting compounds can suppress or enhance ion formation and distort measured amounts.
Electron ionization: An ionization method that bombards gas-phase molecules with energetic electrons, often producing fragment ions. Its reproducible fragmentation patterns make many small molecules identifiable.
Liquid chromatography–mass spectrometry: An analytical method that separates compounds by liquid chromatography before mass spectrometric detection. Chromatographic separation helps analyze complex mixtures before ions reach the mass analyzer.
Ion: An atom or molecule with a net electrical charge from losing or gaining electrons or other charged particles. Mass spectrometry requires charged species so electric and magnetic fields can manipulate them.
Infrared spectroscopy: A spectroscopy method that measures how molecules absorb infrared radiation at vibrational frequencies. Its bond-vibration signatures complement the mass and fragmentation evidence from mass spectrometry.
Ion suppression: A reduction in ionization efficiency caused by competing components in a sample. It is a major source of inaccurate quantification in complex mixtures.

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