Purity, identity, sterility and endotoxins: different questions

Laboratory quality evaluation uses different methods to answer different questions. One result cannot substitute for every other test.

VALREXA Biosciences · 4 min read · November 2026

Purity and identity

Purity testing evaluates the relative presence of components under a given method. Identity testing investigates whether the substance matches the intended molecular structure, often using mass spectrometry or other independent techniques.

Sterility

Sterility testing is designed to detect viable microorganisms under defined conditions. A clean-looking sample or high chromatographic purity does not demonstrate sterility.

Endotoxins

Bacterial endotoxins are components of certain bacteria. Endotoxin testing is distinct from sterility testing, and a sterile sample may still contain endotoxins.

Interpreting a report

A useful laboratory report identifies the sample, method, units, acceptance criteria, limitations and laboratory. Results should be read within the scope of the method actually used.

Further reading

1. USP: Standards and quality resources
2. FDA: Pharmaceutical quality

These are authoritative background resources rather than citations to a specific experimental finding. This guide is educational, not medical advice, and does not endorse the use of experimental compounds.