Gonadorelin — analytical characterisation
Chromatographic conditions, identity, related substances, presentation, reconstitution and in-use stability.
§6Analytical characterisation
§6.1Chromatographic conditions
- Column
- C18, 4.6 × 250 mm, 5 µm
- Mobile phase and gradient
- A: 0.1 % trifluoroacetic acid in water; B: acetonitrile. Gradient 12–40 % B over 25 min
- Detection
- UV 214 nm; 280 nm strong (Trp3, Tyr5)
- Retention
- Intermediate
§6.2Identity by mass spectrometry
[M+H]⁺ at m/z 1183.6; [M+2H]²⁺ at m/z 592.3. Average mass 1182.3 ± 1 Da.[3]
§6.3Related substances and degradation
Table 7. Related substances recorded for Gonadorelin, with the process or storage route that generates each and its analytical signature.
| Related substance | Origin | Analytical signature |
|---|---|---|
| Free glutamate at the N-terminus instead of pyroglutamate | Incomplete cyclisation | +18 Da; the pyroglutamate is essential and the open form is inactive |
| C-terminal free acid | Incomplete amidation | +0.98 Da; the C-terminal Gly-NH₂ is essential and its loss abolishes activity |
| Trp3 oxidation | Oxidation and light | +16 and +32 Da |
| Des-Gly10 nonapeptide | Incomplete coupling or degradation | −57 Da |
| Acetate counter-ion | Commonly supplied as the acetate | Content should be quantified |
Degradation routes
- Cleavage at Trp3-Ser4 and Tyr5-Gly6 in aqueous solution
- Tryptophan oxidation
- Hydrolysis of the C-terminal amide
- Opening of the pyroglutamate ring under alkaline conditions
§7Presentation, reconstitution and storage
§7.1Presentation and reconstitution
- Presentation
- Lyophilised powder for reconstitution
- Reconstitution
- A 5 mg vial with 2.5 mL gives 2 mg/mL; a 100 µg diagnostic dose is 0.05 mL, that is 5 units on a U-100 syringe.
- Storage, lyophilised
- 2–8 °C for authorised presentations; −20 °C for research material
- Storage, reconstituted
- Use promptly; the peptide is cleaved in aqueous solution and no extended in-use claim is supported
- In-use period
- No supported claim beyond same-day use
Gonadorelin is a useful closing example for this series because its pharmacology depends on something no certificate of analysis can capture: the temporal pattern of administration. Analytical quality is necessary but not sufficient for a compound to do what a user expects of it.
§7.2In-use stability
Applicable standards: CEI-MS-01 · CEI-MS-02 · CEI-MS-03 · CEI-MS-04 · CEI-MS-05 · CEI-MS-06. The full series is at methodological standards.
Working calculators: reconstitution and insulin-unit conversion · purity against peptide content · certificate minimum-data checker.
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.
- 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
- 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
- International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q6B Specifications: Test Procedures and Acceptance Criteria for Biotechnological/Biological Products. ICH Harmonised Tripartite Guideline 1999;Step 4 version. identifier not held by the Institute
- International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use. ICH Q1A(R2) Stability Testing of New Drug Substances and Products. ICH Harmonised Tripartite Guideline 2003;Step 4 version. identifier not held by the Institute
- Manning MC, Chou DK, Murphy BM, Payne RW, Katayama DS. Stability of protein pharmaceuticals: an update. Pharmaceutical Research 2010;27(4):544–575. doi:10.1007/s11095-009-0045-6 · PMID 20143256
Identifiers are reproduced only where the Institute holds them. Where a digital object identifier or PubMed identifier is not shown, the Institute has recorded the journal and year and has not constructed an identifier.