Research Peptide Glossary

The vocabulary that appears on a Certificate of Analysis, a supplier specification, or a chromatogram — defined in plain language. This glossary describes how research compounds are measured and documented. It does not describe how any compound is used.

Composition & Purity

Purity

The proportion of the detected material in a tested batch that is the target compound, as measured by a stated analytical method — for peptides, usually HPLC. A result of “≥ 99%” means that, by that method, the target peptide accounts for at least 99% of the detected material. Our guide to what “≥99% purity” really means works through how that figure is calculated and what it does not cover.

What purity is not. Purity describes composition — what is in the vial. It is not a statement about safety, suitability, efficacy, or fitness for any purpose.

Identity

Confirmation that the compound in the batch is the compound the label claims. Identity is a different question from purity, and is established with a mass-based method such as mass spectrometry. A sample can report high chromatographic purity and still be the wrong molecule — which is why purity and identity are reported together.

Net peptide content

The proportion of the dried powder that is actually peptide, as opposed to water and counter-ion salts that are also present in the material. This is a distinct measurement from chromatographic purity: a peptide can be highly pure by HPLC while the dried powder still contains a meaningful fraction of non-peptide mass. Net peptide content is typically determined by quantitative amino acid analysis.

Peak area percent (area %)

The way chromatographic purity is expressed. The detector response is integrated across the chromatogram, and the target compound’s peak is reported as a percentage of the total detected peak area. “98.5% (area %)” means the target peak accounts for 98.5% of the detected, UV-absorbing material.

Purity tiers

Suppliers commonly describe material in composition bands — for example crude, desalted, and higher-purity grades. These labels are descriptions of composition, not regulatory categories, and they are not standardised across suppliers. Read the stated percentage and the method that produced it rather than relying on a grade name. BME Health states the method and result for each batch on its Quality & Testing page.

Analytical Methods

HPLC (High-Performance Liquid Chromatography)

The primary method used to assess peptide purity. A sample is separated into its components as it passes through a column, and a detector records each species as a peak. Purity is calculated from the relative peak areas. Our guide to how research peptides are tested follows an HPLC run and the supporting methods in sequence.

RP-HPLC (Reverse-phase HPLC)

The most common HPLC configuration for peptides, typically run on a C18 column using an acetonitrile–water gradient with trifluoroacetic acid (TFA) as the acidic modifier.

Detection wavelength (214–215 nm)

Peptide analysis is commonly monitored in the region of 214–215 nm, because this range is well suited to detecting the peptide bond and therefore registers the peptide species present in a sample.

Mass spectrometry (MS)

An analytical method that measures the mass-to-charge ratio of a compound. For peptides it is used to confirm identity, by comparing the measured molecular weight against the expected value for the target sequence.

LC-MS

Liquid chromatography coupled to mass spectrometry: the sample is separated chromatographically and the separated species are then measured by mass. It links a chromatographic peak to a mass, which is why it is useful for interrogating purity and identity together.

MALDI-TOF

Matrix-Assisted Laser Desorption/Ionisation – Time of Flight. A mass-spectrometry technique used to determine the molecular weight of a peptide from a small quantity of sample.

Amino acid analysis (AAA)

A method in which the peptide is hydrolysed into its constituent amino acids, which are then separated and quantified. It is the method used to establish net peptide content.

Documentation

Certificate of Analysis (COA)

A batch-linked document summarising the analytical testing performed on one specific batch of material: what was tested, by what method, and with what result. A COA is a summary certificate — it may include or reference the underlying data, such as a chromatogram or a mass spectrum.

A COA is only meaningful for the batch it names. See how to read a peptide COA for a field-by-field walkthrough.

Batch / lot number

The identifier that ties a COA to a specific production run of material. Because analytical results describe the batch that was tested, the batch identifier on the certificate is what connects the document to the material in hand.

Chromatogram

The graphical output of a chromatographic separation, plotting detector response against time. Each peak represents a detected species. A high-purity sample typically shows one dominant peak with comparatively small additional peaks.

Third-party testing

Analytical testing performed by a laboratory independent of the supplier. It is a documentation practice: it describes who generated the result — not a claim about the material’s safety or suitability.

ISO/IEC 17025

An international standard covering the competence of testing and calibration laboratories. Where a testing laboratory holds accreditation to this standard, it speaks to that laboratory’s testing competence. It is not a statement about any product.

Impurities

Impurities are the non-target species that appear alongside the intended compound. On a chromatogram they are the peaks that are not the main peak — together they account for the remaining share of the purity percentage. Common categories in synthetic peptides include:

Truncated sequences

Peptide chains where synthesis stopped short, producing a shorter sequence than intended.

Deletion sequences

Chains missing one or more internal amino acid residues relative to the target sequence.

Oxidation

The addition of oxygen to susceptible residues, which shifts the observed mass upward — commonly by around 16 Da per oxygen added — and can appear as a distinct species by mass spectrometry.

Deamidation

Conversion of an amide side chain to an acid, producing a small upward mass shift, commonly around 1 Da relative to the target.

Residual solvents

Traces of the solvents used during synthesis and purification that may remain in the dried material. Where a COA reports them, it names the solvents tested for.

Physical Form

Lyophilization (freeze-drying)

The process of removing solvent from a frozen solution under vacuum, leaving a dry powder. Research peptides are commonly supplied in this lyophilized form.

Lyophilized powder

The dry solid that results from lyophilization. Its total mass includes the peptide together with water and counter-ion content — which is why net peptide content is a separate measurement.

Counter-ion

A salt species that remains associated with the peptide after purification. Trifluoroacetate (TFA) is the most common, arising from the acidic modifier used in reverse-phase purification; acetate is an alternative form. Counter-ions add mass to the dried powder without being peptide.

Reconstitution

In laboratory terminology, the step of returning a lyophilized powder to solution by adding a solvent. BME Health provides a reference calculator for the arithmetic involved in expressing concentrations. Neither the calculator nor this glossary provides usage, dosing, or administration guidance of any kind.

Storage (of inventory)

The conditions under which material is held. Lyophilized material and material in solution have different stability characteristics, and a supplier specification will state the storage condition to which its data apply.

Supply Terminology

Research Use Only (RUO)

A supply and labelling designation indicating that material is intended for laboratory research purposes only — not for human or veterinary consumption, and not for clinical use. Every compound supplied by BME Health carries this designation. See our Research Use Disclaimer.

Specification

The set of properties a supplier states for a product — for example the purity threshold, the physical form, and the molecular weight. A specification states what the material is expected to meet; a COA reports what a specific batch was measured to be.

Peptide

A chain of amino acids linked by peptide bonds. Chain length distinguishes peptides from larger proteins, though the boundary is a matter of convention rather than a strict rule.

Sequence

The order of amino acid residues in a peptide, conventionally written from the N-terminus to the C-terminus. The sequence determines the expected molecular weight, which is what identity testing checks against.

Molecular weight

The mass of one molecule of the compound, usually expressed in daltons (Da). It is the expected value against which a measured mass is compared during identity confirmation.

Solid-phase peptide synthesis (SPPS)

The standard method for producing synthetic peptides, in which the chain is assembled stepwise while anchored to a solid resin support, then cleaved from the resin and purified.

Where These Terms Appear

Most of the vocabulary on this page exists to describe one thing: what is actually in a given batch of material, and how that was measured. To see how those measurements are reported in practice, our guide to reading a peptide Certificate of Analysis walks through the document field by field, and our Quality & Testing page documents how BME Health handles batch-level testing and COA access.

You can also browse our research guides or the documented catalog.