Analytical chemists work at every stage of development of a medicine, from identifying the structure of a compound that has been made for the first time, to checking the purity of a batch of medicine that is about to be released for sale.

Every batch of the compound that is made at all stages of development of the medicine must be checked for purity.  A range of analytical techniques will be used, one of the most common is high pressure liquid chromatography (HPLC) linked to a mass spectrometer (MS). By linking the two machines it makes it easier to identify any impurity in the compound that is being tested.

Tests are carried out on the actual chemical compound that is the active medicine (the active pharmaceutical ingredient - API) and on the medicine once it has been formed into the dosage form - such as a tablet, capsule or ointment.