Mass spectrometry
Mass spectrometry is an analytical technique that identifies and measures molecules by turning them into ions and sorting them by their mass-to-charge ratios.
What mass spectrometry is
Mass spectrometry is a way to identify and measure chemical substances by their ions. A mass spectrometer does not simply weigh a molecule like a scale. It turns molecules or atoms into charged particles, moves those ions through electric or magnetic fields, and records how they behave according to mass-to-charge ratio.
From sample to ions
The first challenge is ionization: giving molecules a charge without destroying the information scientists need. Some methods are harsh and break molecules into fragments, which can be useful for identification. Others are soft, preserving large biomolecules such as peptides and proteins well enough for biological analysis.
Mass analyzers
After ionization, a mass analyzer separates ions. Different instruments use different physics. Quadrupoles filter ions with oscillating electric fields, time-of-flight analyzers compare how quickly ions travel, ion traps hold and release ions, and magnetic or electrostatic sectors bend ion paths. Each design has tradeoffs in speed, resolution, sensitivity, and cost.
Reading a mass spectrum
The result is a mass spectrum: peaks arranged by m/z with intensities that reflect how many ions were detected. A peak can represent a molecular ion, an isotope pattern, or a fragment. Scientists compare spectra with databases, standards, and chemical reasoning to identify compounds and estimate amounts.
Tandem mass spectrometry
In tandem mass spectrometry, often written MS/MS, selected ions are isolated, fragmented, and measured again. This adds structural information. It is especially useful when many compounds are mixed together, such as in blood, food, environmental samples, or proteomics experiments that try to identify thousands of peptides.
Coupled separations
Many real samples are too complex to send directly into a mass spectrometer. Instruments are often coupled to chromatography, such as liquid chromatography or gas chromatography, to separate compounds before mass analysis. The separation step reduces confusion and lets the mass spectrometer measure more components in a mixture.
Applications
Mass spectrometry helps test drug purity, measure pollutants, identify unknown chemicals, study proteins and metabolites, date geological materials, monitor food safety, detect explosives, and investigate disease biomarkers. Space missions also use mass spectrometers to study atmospheres, gases, dust, and possible chemical clues on other worlds.
Why it matters
Mass spectrometry matters because many important questions are molecular questions: what is present, how much is there, where did it come from, and how did it change? The technique connects physics and chemistry to practical evidence, turning tiny amounts of material into readable patterns that can guide science, medicine, law, and environmental decisions.