mass analyzer
/ mass AN-uh-ly-zer /
Imagine a postal sorting machine that takes a jumble of parcels and routes each one to the right bin purely by its weight — heavy boxes one way, light envelopes another — so that by the end, everything of the same weight has landed together. The mass analyzer is the heart of a mass spectrometer that does this sorting, except it sorts ions by their mass-to-charge ratio rather than parcels by weight.
Concretely, the mass analyzer is the component that separates ions according to their m/z using electric or magnetic fields. Different designs achieve this in different ways: a quadrupole steers ions through oscillating fields and lets only one m/z through at a time, a time-of-flight tube times how long ions take to fly a fixed distance, and other types trap ions and listen to their motion. The detector then counts what the analyzer delivers.
It matters because the analyzer sets two key abilities of the whole instrument: its resolution (how finely it can tell close masses apart) and its mass range (the heaviest and lightest ions it can sort). The caveat is that no single analyzer is best at everything — choosing one is always a trade-off between resolution, speed, mass range, and cost.
In a benchtop instrument, the mass analyzer is the quadrupole sitting between the ion source and the detector; ions of the wrong m/z crash into its rods and never make it through, so only the chosen mass reaches the counter.
The mass analyzer sorts ions by m/z before they reach the detector.
A mass analyzer and a detector are different parts: the analyzer separates ions by m/z, while the detector simply registers how many ions arrive. Many modern instruments chain two analyzers together for tandem experiments.