MRM (Multiple Reaction Monitoring)
Definition
A targeted MS/MS scan mode on a triple quadrupole that monitors specific precursor-to-product ion transitions, with two transitions per analyte (quantifier and qualifier) plus a deuterated internal standard treated as the BSA 2023 Section 63 minimum for confirmatory toxicology reports in India.
- Instrument
- Triple quadrupole mass spectrometer
- Transitions per analyte
- Minimum two: quantifier and qualifier
- Confirmation requires
- Two transitions plus retention-time match
- Common use
- Opioid and toxicology analysis
Common questions
How is MRM different from a regular MS scan?+
MRM filters for specific ion pairs on a triple quadrupole instrument. The first filter (Q1) catches a chosen precursor ion, the collision cell breaks it apart, and the third filter (Q3) catches a specific product ion. This targeting gives much higher sensitivity and specificity than scanning all ions.
Why do forensic labs use two transitions per substance in MRM?+
One transition is the quantifier (measures how much substance is present), and one is the qualifier (confirms you have the right substance). Combined with a retention-time match, two transitions are the standard requirement to confirm identification and rule out false positives.
What's an MRM transition exactly?+
It is one precursor-to-product ion pair. A transition tells the instrument to select ions of mass X in Q1, fragment them in the collision cell, then select ions of mass Y in Q3. Each substance gets at least two transitions running at the same time.
Related terms
- 4-Anilinopiperidine Scaffold
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- Alkaloid Ratio Profiling
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- Atmospheric Pressure Chemical Ionisation (APCI)
- A complementary atmospheric-pressure source that vaporises the LC eluent and uses a corona discharge to ionise a reagent gas, which transfers charge...
- ATR (Attenuated Total Reflectance)
- An FTIR sampling mode in which the sample is pressed against a diamond or ZnSe crystal and the evanescent wave probes the...
- Beer-Lambert Law
- A = εbc. Absorbance equals molar absorptivity times path length times concentration. The linear relation between absorbance and concentration that makes UV-Vis...
- Carfentanil
- A fentanyl analogue with a 4-carbomethoxy substituent on the piperidine ring; approximately 10,000 times the analgesic potency of morphine. Implicated in the...
- CID and HCD
- Collision-induced dissociation. The precursor is accelerated and collides with a neutral gas (nitrogen, argon, helium) in the collision cell. Internal energy converts...
- Deuterated Internal Standard
- An isotopologue of the analyte where two to five hydrogens are replaced by deuterium. Same chromatographic and ionisation behaviour, slightly higher mass....
- Diacetylmorphine
- The IUPAC name for heroin; the 3,6-diacetyl ester of morphine, produced by acetylation with acetic anhydride. More lipophilic than morphine, crosses the...
- Dose Heterogeneity
- The variation in active ingredient content between nominally identical tablets in a counterfeit or clandestinely pressed batch. High dose heterogeneity in illicit...
Explained in these topics
- Hyphenated Techniques: GC-MS, LC-MS and GC-FTIRA targeted MS/MS scan mode on a triple quadrupole that monitors specific precursor-to-product ion transitions, with two transitions per analyte (quantifier and...
- Opioids: Heroin, Fentanyl Analogues and Prescription DiversionsAn LC-MS/MS acquisition mode selecting a precursor ion and one or more product ions for each analyte. Provides high sensitivity and specificity for quantitativ...
- Spectrometric Detection: UV-Vis, FTIR and Mass SpectrometryA triple-quadrupole LC-MS/MS acquisition mode that filters a precursor ion in Q1, fragments it in Q2 and filters a product ion in Q3. Each precursor-to-product...
- Tandem Mass Spectrometry (MS/MS) and Spectral InterpretationA targeted MS/MS mode on a triple quadrupole. Q1 is parked on a chosen precursor m/z, the collision cell fragments it, Q3 is parked on a chosen product m/z. Tw...