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Tandem mass spectrometry
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<p>Tandem mass spectrometry, also known as MS/MS or MS2, is a technique in <a href="/facts/Instrumental_analysis/AFVUB1Ac">instrumental analysis</a> where two or more stages of analysis using one or more <a href="/facts/Mass_spectrometry/RH5WBHJ2">mass analyzer</a> are performed with an additional reaction step in between these analyses to increase their abilities to <a href="/facts/Analytical_chemistry/MHQf3YP6">analyse</a> chemical samples. A common use of tandem MS is the analysis of <a href="/facts/Biomolecule/DGvFzN7R">biomolecules</a>, such as <a href="/facts/Protein/Jxmagu3E">proteins</a> and <a href="/facts/Peptide/C4ltc7UG">peptides</a>. </p><p>The <a href="/facts/Molecule/N9ljSfFq">molecules</a> of a given sample are <a href="/facts/Ionization/W13Ceavd">ionized</a> and the first spectrometer (designated MS1) separates these <a href="/facts/Ions/wrbwhF3z">ions</a> by their <a href="/facts/Mass-to-charge_ratio/QaKpLt6B">mass-to-charge ratio</a> (often given as m/z or m/Q). Ions of a particular m/z-ratio coming from MS1 are selected and then made to split into smaller <a href="/facts/Fragmentation_(mass_spectrometry)/Gbul2wLR">fragment ions</a>, e.g. by <a href="/facts/Collision-induced_dissociation/tPJBSbhR">collision-induced dissociation</a>, <a href="/facts/Gas-phase_ion_chemistry/mBEdo2FL">ion-molecule reaction</a>, or <a href="/facts/Photodissociation/nzRyzh8I">photodissociation</a>. These fragments are then introduced into the second mass spectrometer (MS2), which in turn separates the fragments by their m/z-ratio and <a href="/facts/Mass_spectrometry/RH5WBHJ2">detects</a> them. The fragmentation step makes it possible to identify and separate ions that have very similar m/z-ratios in regular mass spectrometers. </p>