A glossary of research peptide terms

The vocabulary of analytical testing is dense and often used loosely. This glossary defines the terms you will meet on a peptide certificate of analysis and a product page, in the order you are most likely to encounter them.

Certificate of analysis (CoA)

The document reporting the identity and purity results for a specific batch of material. It is tied to a batch number and should be independently checkable. See how to read a certificate of analysis.

Batch (lot)

A single production run of material. Results apply to the batch, not to a brand in general, which is why the batch number must match between the certificate and the vial.

HPLC (high-performance liquid chromatography)

The separation technique used to measure purity. A sample is pushed through a column and the components elute at different times, producing a chromatogram. See HPLC purity explained.

Chromatogram

The trace produced by an HPLC run: peaks plotted against time. The area under the main peak relative to all peaks gives the purity percentage.

Retention time

The time at which a component elutes from the column. It helps identify a peak when compared against a reference standard.

Resolution

How well two neighbouring peaks are separated. Poor resolution means an impurity may be hiding inside, or merged with, the main peak.

Related substances

Chemical variants and fragments close to the target molecule. They can be present without the purity percentage making them obvious.

Mass spectrometry (MS)

The technique used to confirm identity by measuring the mass of the ions formed from a sample. The observed mass is compared with the theoretical mass of the intended sequence. See peptide identity and mass spectrometry.

Molecular mass

The mass of the molecule, used as the expected value that a mass-spectrometry result is checked against.

Sequence

The order of amino-acid units in a peptide. Sequence confirmation is the deepest level of identity testing, usually done by breaking the peptide into fragments (MS/MS).

Purity

The proportion of the sample represented by the main peak, expressed as a percentage. A relative, method-dependent figure rather than an absolute measure of substance.

Lyophilised

Freeze-dried: the dry powder form in which peptides ship and store best. See lyophilised vs reconstituted peptides.

Reconstitution

Dissolving a lyophilised powder into a solvent to make a working solution. See reconstituting research peptides.

Bacteriostatic water

Water containing a small amount of benzyl alcohol, which slows microbial growth so a solution can be kept for a period after it is made.

Cold chain

The temperature-controlled handling of material from dispatch to delivery, so a shipment arrives within the conditions the material needs.

Certificate verification host

An independent system, run by the testing laboratory rather than the seller, where certificates are published so a buyer can check them without relying on the seller's own site.

If you want to put these terms to use, the lab test results page lists our published batches, and the rest of the research notes build on the definitions above.