Ammonium Adduct [M + NH4]+
Definition
The dominant ionisation form of TATP in positive-mode ESI LC-MS when ammonium acetate or formate is present in the mobile phase. TATP molecular weight is 222, so [TATP + NH4]+ appears at m/z 240. Used as the precursor ion in SRM-mode confirmation.
- Adduct ion
- [M + NH4]+
- TATP monoisotopic mass
- 222 Da
- Observed m/z
- 240
- Ionisation mode
- Positive-mode ESI
- Mobile phase additive
- Ammonium acetate or ammonium formate
Common questions
Why does TATP not form a simple protonated [M+H]+ ion?+
TATP has no basic nitrogen or readily protonated site, so it ionises poorly by direct protonation. Adding ammonium salt to the mobile phase supplies NH4+ that attaches to the peroxide oxygens, giving a stable, abundant precursor ion for MS detection.
How is the adduct used in confirmatory testing?+
In SRM mode the m/z 240 precursor is selected and fragmented; the resulting product ions are matched against a reference spectrum. Two or more qualifying transitions from this precursor support a confirmatory identification of TATP under most forensic lab protocols.
Related terms
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