A pharmaceutical company produces a painkiller tablet. Quality control scientists use gas chromatography–mass spectrometry (GC-MS) to check that the tablet contains only the correct compounds and no contaminants. Explain how GC-MS allows scientists to identify each compound present in the tablet and state two advantages of using this instrumental method rather than traditional chemical tests.

In GC, the tablet extract is injected and vapourised. Each compound interacts differently with the column coating and therefore moves at a different speed, giving a distinct retention time. The retention time of each peak is compared with that of known standards to give a first identification.
The eluted compound then enters the mass spectrometer where it is ionised and fragmented. The resulting mass spectrum shows the m/z values of the fragments. This pattern is characteristic of the compound and is matched to a reference library to confirm its identity.
Thus GC-MS combines chromatographic separation (retention time) with structural information (fragmentation pattern) to identify every component.
Advantages:
1. It is highly sensitive, detecting compounds at trace levels that would be missed by routine chemical tests.
2. It can analyse complex mixtures in a single run, giving simultaneous identification of many components.