Reading and Interpreting Certificates of Analysis

A Certificate of Analysis (COA) is the primary document that summarizes quality testing results for a specific product batch. For research peptides, a COA typically includes purity measurements, identity confirmation, and testing methodology. Understanding how to read a COA helps researchers evaluate product quality and make informed purchasing decisions.

Essential COA Components

A complete COA for a research peptide should include:

Product identification — The peptide name or sequence, catalog number, and batch/lot number. This links the COA to a specific production run, not just a generic product.

Purity analysis — HPLC purity expressed as a percentage, along with the method used (e.g., reversed-phase C18, gradient conditions). This is the most commonly referenced data point on a COA.

Identity confirmation — Mass spectrometry results showing observed molecular weight versus theoretical molecular weight. A match confirms the peptide is the correct compound.

Appearance — Physical description of the product (e.g., white lyophilized powder). While basic, this provides a quick sanity check.

Testing laboratory — The name of the lab that performed the analysis. Third-party lab names add credibility; in-house testing alone should be viewed with more scrutiny.

What to Look For

When evaluating a COA, focus on these questions:

Is it batch-specific? The COA should reference a unique batch or lot number that matches your product label.
Is purity stated clearly? Look for a specific percentage (e.g., 98.7%) rather than a vague range (e.g., ">95%"). The HPLC method should be described.
Is identity confirmed? Mass spectrometry data should show observed MW within ±1 Da of theoretical MW.
Who performed the testing? Third-party accredited laboratories provide the highest level of confidence.
When was testing done? The test date should be recent relative to the batch production date.

Common Pitfalls

Generic COAs — Some suppliers issue a single COA for an entire product line rather than per-batch. These are meaningless for quality verification.
Missing methodology — A purity number without the analytical method is unverifiable.
No MS data — HPLC purity alone cannot confirm identity. A COA without mass spec data is incomplete.
Undated documents — Without a test date, there is no way to assess data currency.