Quality & Testing

By the Sequora Research Team · Last updated: October 22, 2026

Peptide purity testing is the reason a research result can be trusted. If the material in the vial is not the sequence on the label, or is mixed with synthesis by-products, the experiment measures the wrong thing. This page explains how we test every batch, what the tests can and cannot show, how to find the certificate for your batch, and how to store lyophilized material so it stays as tested.

Our purity standard

Every compound we list goes through the same release check before it is offered for sale:

• Identity is confirmed. The measured molecular mass must match the expected mass of the stated sequence.
• Purity is measured, not estimated. The certificate reports the HPLC purity of that specific batch as a number, with the chromatogram it came from.
• One batch, one certificate. Each certificate carries a batch number that is printed on the vial label, so the document always matches the material.
• Specifications are checked against public data. Each product page lists the sequence, molecular formula, molecular weight and CAS number, cross-checked against public chemical databases. Our Research Sources & Editorial Standards page explains how we choose and cite those sources.

We do not advertise a single purity figure for the whole catalog. Purity is a property of a batch, so the number that matters is the one on the certificate for the vial in your hands.

Third-party testing

“Third-party tested” means the analysis is done by an independent analytical laboratory, not by the supplier selling the material. The laboratory receives a sample of the batch, runs its methods, and issues the certificate under its own name. That separation matters: a supplier testing its own stock has an obvious conflict of interest, while an outside laboratory does not.

Independent testing does not make a compound suitable for any use outside the laboratory. It answers two narrow questions about a batch: is it the right molecule, and how much of the detectable material is that molecule. Read our Research Use Policy for what our products may and may not be used for.

HPLC peptide testing, explained

High-performance liquid chromatography (HPLC) separates the components of a sample as it moves through a packed column. For peptides the usual method is reverse-phase HPLC with UV detection at around 214–220 nm, the wavelength at which the peptide bond absorbs light.

• What the purity number means. Each component leaves the column at its own time and appears as a peak. Purity is the area of the main peak as a percentage of the total area of all detected peaks.
• What it does not mean. HPLC purity is not the share of the powder that is peptide by weight. Lyophilized peptides also contain counter-ions (such as acetate or trifluoroacetate) and residual water, which do not show up as peptide peaks. That second measure is called peptide content.
• Why the chromatogram matters. A single sharp main peak with small, separated side peaks is easier to interpret than a broad or shouldered peak, which can hide closely related impurities such as deletion or truncated sequences.

Mass spectrometry, explained

HPLC shows how much of the sample is one main component; it cannot say what that component is. Mass spectrometry (MS) answers that question by measuring the mass-to-charge ratio of ionised molecules, from which the molecular mass is calculated.

On the certificate, compare the observed mass with the expected (theoretical) mass of the sequence. A close match confirms identity. A sample can show high HPLC purity and still be the wrong peptide, which is why we require both tests on every batch, never one alone.

Reading the certificate of analysis

A certificate of analysis (COA) is the laboratory’s report for one batch. When you read one, check four things:

1. The batch number matches the label on your vial.
2. The compound name and sequence match the product you ordered.
3. The HPLC purity and the attached chromatogram.
4. The observed mass against the expected molecular weight.

Our full guide, How to read a peptide COA, walks through a certificate line by line, including the difference between purity and peptide content.

Batch numbers and where to find each COA

Every vial label carries a batch code. That code links the vial to the certificate for the batch it came from.

• For a vial you have received: email research@sequorapeptides.com with your order number and the batch number and we will send the matching COA.
• Before you order: email us the product name and strength and we will send the certificate for the batch currently in stock.
• Keep it with your records. We recommend filing the COA with your laboratory notes so the batch can be traced if results need to be checked later.

Peptide storage and handling

Correct storage keeps the material in the same state it was in when it was tested. The guidance below is general laboratory practice for lyophilized research peptides.

Lyophilized (freeze-dried) material

• Store sealed vials at −20 °C or colder for long-term storage, in a dry place, protected from light.
• Short periods at room temperature, such as during shipping, are normal for lyophilized peptides. Move vials to cold storage when they arrive.
• Let a vial reach room temperature before opening it, so moisture from the air does not condense on the cold powder.
• Close the vial promptly; many peptides absorb moisture from the air.

Material in solution

• Peptides in solution are much less stable than the dry powder. Laboratories usually divide a solution into single-use aliquots and keep them frozen.
• Avoid repeated freeze–thaw cycles, which can degrade the peptide.
• Sequences containing cysteine, methionine or tryptophan are more prone to oxidation and are best kept away from air and light.

More storage questions are answered in our FAQ on storage and handling.

Browse tested compounds

Every compound in the compound catalog is tested the same way. Browse by class: GLP-1 receptor agonists, GHRH analogues, neuropeptides, thymosin peptides, copper peptides, mitochondrial peptides and bioregulators.

For laboratory research use only. Not for human or veterinary use.