How to Read a Certificate of Analysis (COA): Researcher’s Guide

What Is a Certificate of Analysis?

A Certificate of Analysis (COA) is a document issued by an analytical laboratory confirming the identity, purity, and quality of a specific batch of peptide. It is the single most important quality assurance document in peptide research.

A proper COA should include: the peptide name and sequence, batch/lot number, testing date, analytical method used (typically HPLC), purity percentage, and mass spectrometry confirmation. Without a COA, there is no way to verify what you are actually working with.

Understanding HPLC Purity

High-Performance Liquid Chromatography (HPLC) is the standard analytical method for measuring peptide purity. The HPLC chromatogram shows peaks representing different compounds in the sample.

The main peak represents your target peptide. Smaller peaks represent impurities (deletion sequences, truncated peptides, or degradation products). Purity is calculated as the area of the main peak divided by the total area of all peaks.

99%+ purity means the main peak accounts for 99% or more of the total sample. This is research-grade quality. Anything below 95% should be questioned for research applications.

Reading the Chromatogram

The x-axis of an HPLC chromatogram shows retention time (minutes). The y-axis shows signal intensity (mAU). Your target peptide will appear as the tallest, sharpest peak.

A clean chromatogram has one dominant peak with minimal noise. Multiple significant peaks suggest impurities or degradation. The retention time should be consistent with the expected value for your peptide — significant deviation may indicate a different compound.

Peptify provides full chromatogram images on every COA, downloadable from each product page.

Mass Spectrometry Confirmation

Mass spectrometry (MS) confirms the molecular identity of the peptide by measuring its molecular weight. The observed mass should match the theoretical mass within instrument tolerance (typically ±0.1%).

For example, BPC-157 has a theoretical molecular weight of 1419.53 Da. The MS reading on your COA should show a value within this range. If the observed mass is significantly different, the sample may not be what it claims.

Batch Numbers and Traceability

Every Peptify batch is assigned a unique lot number. This number links your specific vial to the exact COA, manufacturing date, and testing results.

Keep a record of batch numbers for your research documentation. If you need to replicate results or report findings, batch traceability ensures you can reference the exact material used.

All Peptify COAs are accessible through our product pages. If you ever need a historical COA, contact us with your batch number.