A pharmaceutical company produces a new painkiller tablet. Quality control chemists need to check that the tablet contains the correct substances in the correct amounts. Describe how instrumental analysis could be used to identify and determine the purity of the substances in the tablet, and explain the advantages of using instrumental methods over traditional chemical tests for this purpose.

An example of an instrumental method is gas chromatography (GC) coupled with mass spectrometry (MS). In GC the tablet is dissolved, the mixture is injected and the components are separated by their different affinities for the stationary phase. The MS detector then ionises the eluting compounds and records their mass‑to‑charge ratios, giving a unique mass spectrum for each substance.

GC–MS can detect trace amounts of impurities because the detector is highly sensitive and the chromatographic separation reduces background noise.

The analysis is rapid – a full GC–MS run can be completed in 10–20 min, whereas classical wet‑chemical tests may take hours or days.

The mass spectrum obtained can be matched against a database or library of known spectra, allowing unambiguous identification of the active ingredient and any excipients or contaminants.

Finally, the area under each chromatographic peak is proportional to the amount of that compound present, so GC–MS provides quantitative data that can be used to calculate the purity of the tablet.