Purity Versus Identity in Research-Material Documentation

Two different questions

Identity asks whether analytical evidence is consistent with the expected compound. Purity asks how much of the measured chromatographic signal is attributed to the primary analyte under the method’s rules.

Conflating the two can make a COA look complete when one dimension is missing. Strong procurement practices treat them as complementary.

Typical method pairing

Research-material certificates often report purity via HPLC and identity via mass spectrometry (sometimes as LC-MS). Other orthogonal techniques may appear depending on the laboratory and material class.

Method names matter. A purity percentage without a named method, or an identity claim without technique language, is harder to defend in an audit.

Catalog targets versus lot results

Catalog “target purity” language describes intended specification framing for a SKU. Lot-specific measured values belong on the batch record or COA. Use the lot document for experimental traceability.

A minimal dual-check

Before releasing a lot into a critical series, many labs confirm:

• Identity method named and lot-linked
• Purity method named with lot-specific result when required
• Dates and lot numbers consistent across vial and paperwork
• Archive location recorded for the experiment series