Start with the batch, not the headline percentage
A certificate of analysis (COA) reports results for an identified sample. Match the compound name, size, and lot to the material you are evaluating. Check the issuing laboratory, report date, methods, and units before comparing results.
Use the Next Era Peptide batch certificate library to find current reports and earlier batches. A previous lot's report does not establish a new lot's results. Reconstitution solutions in our catalog are not sent for third-party compound testing.
HPLC purity and peptide quantity are different measurements
When HPLC purity is reported as area percent, it describes the target peak's share of the detected chromatographic signal under that method. It does not automatically give the percentage of peptide by weight in the vial. Water, counterions, detection conditions, and components that the method does not resolve can matter.
NIST's peptide reference-material documentation distinguishes UV absorbance area purity from peptide mass purity. Ask what basis the laboratory used for a reported percentage. NIST RM 8327 analytical definitions.
A high chromatographic purity result is not, by itself, a measurement of the vial's peptide quantity, a sterility result, or an endotoxin screen.
Read identity results with the method
Mass spectrometry can compare observed mass with the expected mass of a compound. Read the laboratory's method and acceptance criteria rather than applying a universal tolerance in daltons. Analytical specificity matters: a matching mass alone should not be treated as proof of every structural detail. FDA/ICH Q2(R2) analytical validation framework.
Check which additional tests were actually performed
| Reported field | Question to ask |
|---|---|
| Purity | What method, detection conditions, and reporting basis were used? |
| Identity | What was measured, and what criteria were used for the comparison? |
| Quantity or content | Is this measured peptide content, total material weight, or a labeled amount? |
| Endotoxin | Is a numerical result and unit reported, and is the method suitable for this sample? |
| Sterility, solvents, metals, or other screens | Was the specific test performed, and what limit or detection threshold applies? |
Missing results do not mean that a test passed. Endotoxin and sterility are separate questions. There is no single endotoxin limit that this guide can apply to every research assay; criteria must fit the material, method, and intended laboratory use. FDA's guidance discusses testing and acceptance criteria for regulated products, not approval of our research materials. FDA endotoxin testing guidance, Edition 2.
A practical document checklist
- Match product, size, lot, and sample identification.
- Read the original report and any laboratory verification link.
- Distinguish reported results from specifications and typical values.
- Keep units attached to each result; compare like measurements.
- Ask the laboratory or supplier about missing methods, unclear fields, or conflicting identifiers.
- Assess the report against your laboratory protocol rather than a universal purity cutoff.
A COA documents the submitted sample and reported tests. It does not establish clinical effectiveness, human-use suitability, or regulatory approval. For the supplier side of this process, read how to evaluate third-party laboratory testing.