Analytical testing terminology for procurement teams

Method families

High performance liquid chromatography separates components in solution and is the usual basis for assay and related substances. Gas chromatography suits volatile analytes and residual solvents. Infrared and nuclear magnetic resonance spectroscopy support identity. Mass spectrometry gives molecular mass and, coupled to chromatography, impurity identification. Karl Fischer titration measures water. Inductively coupled plasma techniques quantify elemental impurities.

Assay, purity and content

Assay is the measured amount of the declared substance against a reference standard, usually on a stated basis such as anhydrous or as-is. Chromatographic purity is a peak-area proportion, not a mass measurement. Content on a dried basis differs from content as received. Always read which basis applies.

Limits, thresholds and criteria

A reporting threshold is the level above which an impurity must be reported; an identification threshold is where its structure must be established; a qualification threshold is where its safety must be justified. An acceptance criterion is the pass or fail limit. Numbers without these words attached are not release decisions.

Method validation vocabulary

Specificity, accuracy, precision including repeatability and intermediate precision, linearity, range, limit of detection, limit of quantitation and robustness describe whether a method can support the limit it is used against. For compendial methods, verification in the laboratory replaces full validation; for in-house methods, validation data should exist.

Reference standards and traceability

Results depend on the standard used. Ask whether a compendial or a characterised in-house standard was applied, and whether its traceability is documented.

Reading the certificate

For each line confirm four things: the test, the method, the acceptance criterion, and the result. If any of the four is absent, the line cannot be evaluated and should be queried before the batch is accepted.