Peptide design, synthesis and testing, explained
A plain guide to how research peptides are built, purified and analysed, and how to read the certificate of analysis that documents a batch.
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How research peptides are made and tested: from synthesis to COA
How synthetic research peptides are assembled and analysed, and what each section of a certificate of analysis records.
HPLC purity vs net peptide content: two numbers that are often confused
In an illustrative example, a batch shows 98% HPLC purity yet only 80% peptide by weight. This page explains why the two figures differ and how to read each on a COA.
Common impurities in synthetic peptides and how labs detect them
The impurities that arise in synthetic peptides, the analytical methods that reveal them, and the narrow scope of the FDA's 2021 impurity thresholds.
Prepared by: Research Desk. Sources are linked for verification.
What DesignPeptide covers
DesignPeptide explains how research peptides are designed, synthesised, purified and tested. It also explains how to read the certificate of analysis (COA) that documents a batch. The pages cover chemistry and analytical methods only. They say nothing about the uses or effects of any compound.
- Solid-phase synthesis. Merrifield's 1963 paper introduced solid-phase peptide synthesis (SPPS). The growing chain is attached to an insoluble resin and built through repeated deprotection and coupling steps, with excess reagents washed away (Merrifield, 1963, bibliographic record).
- Purification and HPLC. As general analytical context, HPLC with a non-polar stationary phase separates peptide-related species by hydrophobicity, with UV detection commonly near 214 nm (220 nm is also used). Area-percent purity compares the peaks the detector can see. It is not necessarily the share of peptide by weight.
- Mass spectrometry. As general analytical context, MS supports identity by comparing expected and observed mass. It does not measure purity on its own, and it cannot tell apart every form with the same mass.
- Impurities. A review of related impurities in peptide medicines describes deletion and insertion sequences, incomplete deprotection, oxidation, deamidation and diastereomers (D'Hondt et al., 2014, PubMed). As general analytical context, side reactions such as racemisation during coupling and aspartimide formation at aspartic acid residues are also widely discussed in peptide chemistry.
- Certificates of analysis. What each field means, which details a useful report includes, and what a COA cannot show.
Who it is for
The site is written for laboratory researchers, students of peptide chemistry and procurement staff who compare batch documents. Technical terms are defined where they first appear. Key claims are linked to sources where available, and points offered as general analytical context without a primary source are marked as such.
Sourcing and documentation
DesignPeptide does not sell peptides. The one research-use-only supplier mentioned is Purita, which publishes COA files for some of its products on its certificates page. Reports are available for some products but not every item, so check the page for the specific material. A mention is not a statement about product quality.
A COA describes only the sample tested and only the tests listed. A report showing HPLC and MS alone, for example, says nothing about water content, counter-ion content or endotoxin. Analytical work on seized falsified peptide products has found impurity profiles that the paperwork did not reveal (Janvier et al., 2018, PubMed). A clean-looking document is not the same as a confirmed result.
Start here
- How research peptides are made and tested: from resin to final report.
- HPLC purity vs peptide content: why the two figures differ.
- Synthetic peptide impurities: common types and how they are detected.
- About DesignPeptide: the site's scope and approach.
Supplier documentation
Purita is a store that sells peptides for laboratory research use only. It publishes a certificates page where reports are available for some products; reports are not yet available for every item, so check the page for the specific material.
Affiliate disclosure: this is a paid link. DesignPeptide earns a commission if a purchase is made through it, at no extra cost to the buyer. A listing is not an endorsement or a statement about product quality. See the affiliate disclosure.