Understanding pharmaceutical ingredient specifications

What a specification actually contains

A usable specification names the material unambiguously, states the applicable tests, names the analytical procedure for each test, and gives the acceptance criterion. A test without a method is not a specification; a limit without a method cannot be verified or disputed.

Typical elements for a small-molecule ingredient

Description and appearance, identity by at least two orthogonal methods such as infrared spectroscopy and chromatographic retention, assay with a stated method and range, related substances with individual and total limits, residual solvents against ICH Q3C classes, water content, residue on ignition or sulphated ash, heavy metals or elemental impurities per ICH Q3D, particle size or polymorphic form where relevant, and microbial limits where the intended use requires them.

What changes for peptides and proteins

Larger molecules need identity confirmed by sequence or mass, peptide content distinguished from chromatographic purity, counter-ion and water content quantified because they materially affect net content, aggregation and variant profiles for proteins, and biological potency expressed in defined units rather than a percentage.

Grade language is not a specification

Terms such as pharmaceutical grade, high purity or research grade carry no fixed technical meaning on their own. They become meaningful only when tied to a named monograph or a written in-house specification with limits.

Common gaps to look for

Purity quoted without the method; a monograph claimed without an edition; limits stated as typical values rather than criteria; missing impurity identification for anything above the reporting threshold; and no statement of which tests are performed on every batch.

How to use it commercially

Agree the specification in writing before ordering, state which document version governs, and require that each batch Certificate of Analysis references that version. Where a supplier proposes a change, treat it as a change-control event and re-assess rather than accepting silently.