High-Performance Liquid Chromatography (HPLC) is the most common method used to assess peptide purity. Understanding the chromatogram is essential when reviewing a Certificate of Analysis.

🔬 What Is HPLC Measuring?

HPLC separates compounds in a sample based on chemical properties. As components pass through the detector, they appear as “peaks” on a chromatogram.

Each peak represents a detected compound.

📊 Key Elements of a Chromatogram

• Retention Time (RT)

The time it takes for a compound to pass through the system.
The primary peptide should have a consistent retention time across batches.

• Main Peak

The largest peak typically represents the target peptide.

• Secondary Peaks

Smaller peaks may indicate:

• Minor impurities

• Residual synthesis fragments

• Degradation products

• Peak Area Percentage

Purity is calculated from the area under the main peak relative to total detected peaks.

Example:

• 98% main peak area = 98% analytical purity.

📈 What To Look For

• Sharp, symmetrical main peak

• Minimal secondary peaks

• Clear labeling of retention time

• Date of analysis

• Testing lab details

⚠ Important Considerations

• Analytical purity ≠ biological activity

• Storage conditions affect stability

• Chromatograms without raw data should be interpreted cautiously

Discussion welcome:

• What purity threshold do you consider acceptable for research?

• Do you prioritise third-party testing?

Research discussion only. No application or dosing conversation permitted.

🧬 2️⃣ Peptide Stability & Storage — What the Research Suggests

Peptide stability is influenced by temperature, moisture exposure, pH, and handling conditions.

Understanding degradation pathways is critical in laboratory settings.

🔬 Lyophilised (Freeze-Dried) Form

Most research peptides are supplied in lyophilised powder form because:

• Water accelerates degradation

• Freeze-drying increases stability

• It improves shelf life under controlled storage

📊 Temperature Considerations

General laboratory guidance suggests:

• Refrigerated storage (2–8°C) helps preserve integrity

• Long-term storage may require freezing

• Repeated temperature fluctuation should be avoided

🧪 After Reconstitution

Once exposed to solvent:

• Hydrolysis risk increases

• Oxidation risk increases

• Stability window shortens

Light exposure and agitation may also influence degradation rate.

🧬 Copper-Bound Peptides (e.g., GHK-Cu)

Copper complexes may be sensitive to:

• pH shifts

• Chelation reactions

• Improper storage containers

Understanding metal ion stability is particularly important.

Discussion prompts:

• What environmental factors are most overlooked?

• How does peptide length influence stability?

Research dialogue only.