HPLC purity and mass spectrometry: how to read a COA

The certificate of analysis (COA) is the document that supports the identity and purity of a lot. The two key assays are high-performance liquid chromatography (HPLC) and mass spectrometry (MS).

In the HPLC chromatogram, the main peak should represent the stated purity percentage — typically ≥98% — and secondary peaks should be minimal and quantified.

Mass spectrometry confirms that the measured molecular weight matches the theoretical value for the sequence. A deviation indicates an incorrect sequence, an unwanted modification or degradation.

A COA without a lot number, without a date or without an attached chromatogram is not verifiable. Always request them before incorporating a compound into your study.