The product ion scan type performs two stages of analysis as shown in the following figure.
In the first stage, the ion source forms ions that enter Q1, which is set to transmit ions of a specific m/z. Ions selected by this first stage of mass analysis are called precursor ions. (As a result, Q1 is referred to as the precursor mass analyzer, and the m/z of ions transmitted by the precursor mass analyzer is referred to as the precursor set mass.) After Q1 selects the precursor ions, they enter Q2, the collision cell.
In the second stage of analysis, ions in the collision cell can fragment to produce product ions. Two processes produce product ions: by unimolecular decomposition of metastable ions or by interaction with argon collision gas present in the collision cell. This latter step is known as collision-induced dissociation (CID). Ions formed in the collision cell enter the product mass analyzer (Q3) for the second stage of mass analysis. The product mass analyzer is scanned to obtain a mass spectrum that shows the product ions produced from the fragmentation of the selected precursor ion.
Experiments that use a product ion scan type can determine the m/z values of all the product ions from a specific precursor. These can be used to identify unknowns or as the basis for developing an SRM experiment.