massspectrometer

A mass spectrometer is an analytical instrument used to measure the mass-to-charge ratio of ions in order to determine molecular weights, compositions, and structures. It typically operates under high vacuum and consists of three main elements: an ion source to generate charged particles, a mass analyzer to separate ions by m/z, and a detector to record ion abundances, yielding a mass spectrum.

In operation, molecules are ionized to form charged species, then accelerated and directed into the mass analyzer. There, electric and magnetic fields cause ions to follow trajectories that depend on their mass-to-charge ratio. The resulting mass spectrum plots signal intensity against m/z, with peaks indicating specific ion species and their isotopic patterns. Ionization methods range from hard techniques like electron impact, which fragment molecules for structural information, to soft techniques such as electrospray ionization and matrix-assisted laser desorption/ionization that preserve molecular ions for large biomolecules.

Mass analyzers vary in design and performance. Common types include magnetic sector, quadrupole, time-of-flight, ion trap, Orbitrap, and Fourier transform ion cyclotron resonance. Each offers different combinations of resolution, mass accuracy, and speed. Detectors, such as electron multipliers or Faraday cups, convert ion signals into measurable electrical currents. Modern instruments often combine multiple analyzers in hybrid configurations to enhance sensitivity and resolution.

Applications of mass spectrometry span chemistry, biology, and materials science. It is widely used in proteomics, metabolomics, pharmaceutical analysis, environmental testing, and isotope ratio measurements. The technology continues to evolve with improvements in ionization methods, high-resolution analyzers, and data interpretation algorithms.