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Mass Spectrometry (MS) Cheat Sheet Cheat Sheet by

Mass Spectrometry (MS) Cheat Sheet

Basic Concepts

Mass Spectr­ometry (MS) is an analytical technique used to determine the molecular mass and structure of a compound.
It involves ionizing a sample, separating the ions based on their mass-t­o-c­harge ratio (m/z), and detecting them to generate a mass spectrum.

Mass Detectors

Electron Multip­lier: Converts ions into electrons, amplifying the signal for detection.
Faraday Cup: Collects and measures the current generated by ions striking a metal surface.
Photom­ult­iplier Tube (PMT): Converts ions into photons, which are then amplified and detected.


Identi­fic­ation of Unknown Compounds: MS can be used to determine the elemental compos­ition and structure of an unknown compound.
Quanti­tative Analysis: MS can measure the abundance of specific compounds in a sample using techniques like Selected Ion Monitoring (SIM) or Multiple Reaction Monitoring (MRM).
Proteo­mics: MS is extens­ively used to analyze proteins, peptides, and post-t­ran­sla­tional modifi­cat­ions.

Ionization Techniques

Electron Ionization (EI): Involves bombarding the sample with high-e­nergy electrons, resulting in the formation of radical cations (M+•).
Electr­ospray Ionization (ESI): Suitable for polar and large molecules. It involves the formation of charged droplets from a nebulized sample, which subseq­uently undergo desolv­ation to form ions.
Matrix­-As­sisted Laser Desorp­tio­n/I­oni­zation (MALDI): Suitable for large biomol­ecules. Involves co-cry­sta­llizing the sample with a matrix compound and using a laser to ionize the analyte.

Tandem Mass Spectr­ometry (MS/MS)

MS/MS involves performing multiple stages of mass spectr­ometry, usually involving precursor ion selection, fragme­nta­tion, and product ion analysis.
Common techniques include Collis­ion­-In­duced Dissoc­iation (CID) and Electron Transfer Dissoc­iation (ETD).

Mass Analyzers

Time-o­f-F­light (TOF): Measures the time taken for ions to reach the detector based on their m/z ratio.
Quadru­pole: Uses a combin­ation of direct current (DC) and radio frequency (RF) voltages to select­ively transmit ions of a specific m/z ratio.
Ion Trap: Uses an electric field to trap and store ions, allowing their m/z ratios to be select­ively scanned.

Data Interp­ret­ation

Molecular Ion (M+•): Represents the intact molecule after ioniza­tion.
Base Peak: The most intense peak in a mass spectrum, assigned a relative abundance of 100%.
Fragme­nta­tion: The process of breaking down the molecular ion into smaller fragments, providing structural inform­ation.
Isotopes: Different forms of an element with varying numbers of neutrons, resulting in peaks at different m/z values.

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