How to read a certificate of analysis (COA)
A certificate of analysis records what was tested on one specific lot, by which method, against which specification, and what was found. Reading it correctly is the difference between a traceable result and an unsupported one.
Lot number and retest date
Every certificate belongs to a single lot. The lot number on the vial must match the lot number on the certificate; if it does not, the document does not describe the material in hand.
The retest date is the point at which the lot must be re-evaluated against its specification, not an expiry. Material stored under the stated conditions is generally re-testable rather than automatically discarded.
Specification versus result
The specification column states the acceptance limit; the result column states the value measured on this lot. A result of "Conforms" is valid for qualitative tests such as identity, while quantitative tests report a number.
Chromatographic purity, largest single unspecified peak, residual solvents, water content and residue on ignition together define the usable quality of the lot for calibration work.
Methods behind the numbers
Identity is established by 1H-NMR and LC-MS in positive electrospray. Assay and related substances are determined by HPLC-UV. Residual solvents follow ICH Q3C limits by GC headspace, and water content by Karl Fischer titration.
Store the certificate alongside the raw data reference in your quality system so any assay result can be traced back to the lot that produced it.