Purity

What it determines

Purity is measured by reversed-phase HPLC with UV detection. The sample is dissolved, injected onto the column, and separated into peaks according to how strongly each component is retained. Every component that absorbs at the monitored wavelength appears as its own peak at its own retention time.

Each peak is integrated, and the area of the main peptide peak is divided by the summed area of all integrated peaks. The result is an area percentage. Related substances such as truncated sequences, deletion products, and oxidized forms appear as separate peaks and are counted in the remainder.

Practical notes

• The identifiers supplied with the sample determine how the result is labeled. A lot number is used where one exists, and a report is issued scoped to whatever identifiers arrive with the material.
• Solubility governs the injection. Material that dissolves poorly in the mobile phase needs a different diluent, which is settled at intake.
• Oxidation and hydrolysis in transit shift the impurity profile, so cold, dry shipping preserves the profile the sample left with.