It is vital that pharmaceuticals are as pure as possible.

This reduces the chance of adverse side effects.

It also makes it easier to ensure that the patient has received the intended dose.

The purity of a compound can be established from its melting point, its boiling point or Thin Layer Chromatography.

If a sample has high purity, it will melt or boil close to the known melting/boiling point.

If a sample has low purity, it will melt or boil over a wide range of temperatures .

The presence of an impurity usually:

Lowers the melting point
Raises the boiling point

Thin layer chromatography is similar to paper chromatography, but instead of paper, a thin layer of powder is coated onto a glass or plastic plate. Different powders and solvents are used, depending on the type of substance being separated. The results for a pure substance should show that:

The substance produces just one spot on the plate
The distance travelled by the substance is identical to a known sample of that substance on the same plate