What Is a Mass Spectrometer? Types & Uses

A mass spectrometer is a laboratory instrument that identifies molecules by measuring their mass. It is one of the most powerful analytical tools in science, able to detect and quantify substances down to astonishingly tiny amounts — used everywhere from drug testing to space missions.

The core principle

You can’t put a molecule on a scale, so a mass spectrometer measures mass indirectly. It works in three stages:

1. Ionisation — the sample is turned into charged particles (ions), often by knocking off or adding electrons.
2. Separation — the ions are sent through electric and/or magnetic fields, which sort them by their mass-to-charge ratio (m/z). Lighter ions and more highly charged ions respond differently, so they separate.
3. Detection — a detector counts the ions at each mass, producing a mass spectrum: a fingerprint of peaks that reveals what the sample contains and how much.

Common types

• Time-of-Flight (TOF) — ions are accelerated and timed over a fixed distance; lighter ions arrive first.
• Quadrupole — four rods create fields that filter ions of a chosen mass.
• Orbitrap and FT-ICR — ultra-high-resolution instruments for demanding research.

These are often paired with a separation step first — GC-MS (gas chromatography) or LC-MS (liquid chromatography) — to handle complex mixtures.

Where it is used

• Pharmaceuticals — drug discovery, purity and metabolite analysis.
• Clinical and forensic labs — toxicology, doping tests, newborn screening.
• Environmental testing — trace contaminants in water, soil and air.
• Proteomics — identifying proteins in biology and medicine.
• Space science — instruments on Mars rovers analyse rock and atmosphere.

Choosing an instrument

Selection comes down to the resolution, sensitivity and throughput you need — and budget. Leading manufacturers include Thermo Fisher Scientific, Bruker, Agilent, Waters and SCIEX. If your lab is evaluating options, our Instruments & Lab section covers the field.

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