Tandem mass spectrometry (MS/MS) is a special type of mass spectrometry that helps identify molecules—especially proteins and peptides—with very high accuracy. It uses two stages of mass analysis instead of one.
Here’s a explanation of how it works:
1. First Mass Analyzer (MS¹)
In the first step, the instrument measures the mass-to-charge ratio (m/z) of all the ionized molecules in the sample.
It then selects one specific ion (called the precursor ion) for further study.
2. Fragmentation
The selected ion is broken into smaller pieces (called fragment ions) by colliding it with a gas (like nitrogen or argon).
This process is called collision-induced dissociation (CID) or collision-induced fragmentation.
3. Second Mass Analyzer (MS²)
The second mass analyzer measures the m/z values of these fragment ions.
Each fragment gives information about the molecule’s structure or sequence.
4. Data Interpretation
By analyzing the pattern of fragments, scientists can determine:
- The amino acid sequence of peptides
- The structure of molecules
- The exact identity of the compound
Example (in simple terms)
Imagine you have a long word, and you want to know what letters it’s made of.
- The first MS picks the whole word.
- The fragmentation step breaks it into smaller letter groups.
- The second MS reads those groups to figure out the original word.
In short:
Tandem mass spectrometry (MS/MS) uses two stages of mass measurement.
The first selects a molecule, the second analyzes its fragments.
This helps find the exact structure or sequence of the molecule—especially useful for identifying proteins, peptides, and complex chemicals.