Selected Reaction Monitoring

During analysis, the instrument first selects a precursor ion associated with the analyte, then uses collision-induced dissociation to generate product ions. Monitoring the resulting precursor-to-product transition links the original molecular signal to a defined fragment. This sequence narrows the measurement to chemically informative ion pairs, helping distinguish the target from unrelated components in the same sample.

Selectivity comes from requiring agreement between precursor-ion selection and a characteristic product-ion transition, rather than measuring all ions indiscriminately. That dual filtering is especially useful when sample components produce overlapping or crowded mass-spectrometric signals. In practice, the method can focus measurement on specified compounds even when the sample composition is complex.

High sensitivity is supported by concentrating the measurement on predefined transitions instead of distributing attention across many possible ions. This targeted strategy allows Selected Reaction Monitoring to detect trace compounds and quantify them in analytical workflows. The resulting measurements can reveal whether a target is present and support comparisons of its amount across samples or conditions.

One transition can provide a focused measurement, while monitoring one or more characteristic product-ion transitions can add information for molecular-identity verification. The relevant precursor-to-product pairs are chosen for the compound being studied, so the transition pattern becomes part of the analytical evidence. This is useful when researchers need both detection and confidence that the measured signal belongs to the intended analyte.

A typical workflow begins by specifying the target compound and its precursor ion, followed by selecting the relevant product-ion transition or transitions. The instrument then isolates the precursor, applies collision-induced dissociation, and records the selected transitions. Researchers use the resulting measurements to detect, quantify, or verify targets, depending on the analytical question.

Triple-quadrupole instruments are often used because their configuration supports sequential ion selection, fragmentation, and monitoring of selected ion pairs. This arrangement matches the method’s targeted logic: one stage isolates the precursor, collision-induced dissociation creates fragments, and a later stage monitors the chosen product ions. It is therefore suited to focused quantitative measurements.

In chemistry, Selected Reaction Monitoring supports measurements across pharmaceutical research, environmental testing, and biological studies. Researchers can use it to assess changes in sample composition, measure trace compounds, or verify molecular identity. Its value is greatest when the study requires targeted information about particular analytes rather than an unrestricted survey of every compound present.