CEI-MS-03 — Determination of peptide content and its distinction from chromatographic purity

§1Scope

§1.1Scope

Applies to all synthetic peptides supplied as lyophilised powders. Establishes the Institute’s position that purity and content are independent quantities and that a certificate reporting one without the other is incomplete.

§2Principle

A lyophilised peptide preparation consists of the target peptide, related peptide impurities, water, counter-ion, and any residual excipient or solvent. Chromatographic purity describes the proportion of the peptide fraction that is the target sequence. Peptide content describes the proportion of the total mass that is peptide at all. A preparation may be 99 % pure and 72 % peptide by content, and a vial labelled 5 mg then contains 3.6 mg of peptide of which 3.56 mg is the target sequence.^[1,2]

§3Apparatus and reagents

§3.1Apparatus

• HPLC system as CEI-MS-01, for quantitative assay against a reference standard
• Analytical balance readable to 0.01 mg, calibrated, in a draught-free enclosure
• Karl Fischer titrator or thermogravimetric analyser for water determination (CEI-MS-04)
• Ion chromatograph or capillary electrophoresis system for counter-ion determination (CEI-MS-10)
• Nitrogen analyser or amino-acid analyser as an alternative content method

§3.2Reagents and reference materials

• Reference standard of the peptide with an assigned content value and a stated assignment basis
• Reagents as required by the selected content method

References cited on this page

References are numbered in order of first citation in this document. Each superscript in the text links to its entry below.

1. United States Pharmacopeial Convention. General Chapter ⟨1225⟩ Validation of Compendial Procedures. United States Pharmacopeia — National Formulary (USP–NF) 2024;USP 2024 Issue 1. identifier not held by the Institute
2. International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q2(R2) Validation of Analytical Procedures. ICH Harmonised Guideline 2023;Step 4 version, 1 November 2023. identifier not held by the Institute

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