Test methods explained

What the tests on a report measure, and what they can't tell you. Not every report includes every test; each one lists exactly what was tested.

Purity by HPLC

High-performance liquid chromatography separates the sample into its components and records them as peaks over time. Purity is the main peak's share of the total peak area, given as a percentage.

It shows what share of the detected signal sits in the main peak. On its own it doesn't confirm that the main peak is the target peptide, or how much peptide is in the vial.

Identity by mass spectrometry

Mass spectrometry measures the mass of the molecules in the sample. The observed mass is compared with the theoretical mass of the expected peptide, worked out from its sequence. A match within the instrument's tolerance supports identity, though mass alone can't tell apart molecules of the same mass.

Peptides often appear as several charged forms, so a report may list more than one value. Each should point back to the same molecular mass.

Peptide content

Content is the amount of peptide found in the vial, in milligrams, compared with the amount on the label. A vial can be high in purity and still hold less than it states, which is why content is tested separately.

What a report can't show

A report describes the sample the laboratory received from the seller. It can't speak for storage after it left our hands, and it says nothing about suitability for any use outside the laboratory.