LC-MS/MS (Negative ESI)
Definition
Liquid chromatography with tandem mass spectrometry in negative-ion electrospray ionisation mode. Confirmatory method for all conventional secondary explosives and the primary method for PETN (which can thermally degrade on GC injector ports). MRM acquisition with two transitions per analyte provides compound-specific confirmation.
- Ionisation mode
- Negative electrospray ionisation
- Primary use
- Confirmation of secondary explosives
- Key analyte
- PETN
- Confirmation basis
- Two MRM transitions per analyte
Common questions
Why is negative ESI used instead of positive ESI for these explosives?+
Nitrate ester and nitramine explosives such as PETN and RDX ionise more efficiently by losing or attracting electrons under negative conditions than by gaining a proton, so negative-mode electrospray gives stronger, more reliable signals for this compound class.
Why require two MRM transitions rather than one?+
A single transition can occasionally be matched by an unrelated interfering compound. Requiring two independent fragment-ion transitions from the same parent ion, both at the correct ratio, guards against a false identification in a complex or contaminated sample.
Related terms
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