The Hidden Passenger: Understanding Mass Spectrometry Adducts

Adducts: Finding the Molecule Hidden Inside the Ion A beginner-friendly visual lesson about why a mass spectrometer measures ions, what m/z means, and how [M+H]+, [M+Na]+, and [M-H]- relate to the original neutral molecule. Watch a proton or sodium ion change the observed peak, reverse the calculation to recover neutral mass, and see why an incorrect ion label can send an MS/MS candidate search to the wrong place. Includes three active-recall questions. 00:00 The Hidden Molecule 00:32 Why Charge Matters 01:16 What The Instrument Reports 02:00 Meet The Passengers 02:59 From Molecule To Peak 03:58 From Peak Back To Molecule 04:40 Why The Label Matters 05:21 Connecting To Ms/Ms 06:09 The Mental Model 06:47 Test Your Mental Model 07:48 Who Was The Traveler? Scientific notes • Examples use single-charge ions and an illustrative neutral monoisotopic mass of 180.0634 Da. • Proton mass contribution: approximately 1.007276 Da. • Sodium-ion mass contribution: approximately 22.989218 Da, not the neutral sodium-atom mass. • Positive and negative examples are shown as separate polarity spectra. • Molecules and instrument paths are conceptual schematics, not literal chemical structures or a model of a particular instrument. • Neutral-mass agreement and fragment similarity support identification; neither alone proves a unique structure. Source: ACD/Labs, Common Adduct and Fragment Ions in Mass Spectrometry https://www.acdlabs.com/blog/common-a... Original visual animation created with Manim Community. Narration generated with ElevenLabs. No affiliation with 3Blue1Brown.