Peptide HPLC purity is commonly reported as a percentage of integrated detector area. Read that percentage with its method and chromatogram; it is a different measurement from milligrams of peptide per vial.
What the percentage counts
In liquid chromatography, components pass through a separation system and a detector records a response over time. An area-normalised purity result compares the area assigned to the target with the included integrated peak area. Detector choice, wavelength, separation and integration rules affect that comparison.Agilent LC handbook (opens in a new tab)Bachem analytical guide (opens in a new tab)
For an illustrative calculation, a target peak area of 9,600 within a total included area of 10,000 gives 96.0% area purity. If a peak is excluded, the denominator changes. Equal detector areas also need not represent equal material amounts when components have different responses.Bachem analytical guide (opens in a new tab)Agilent LC handbook (opens in a new tab)
Read the supplied Semax trace
| Field | Reported detail |
|---|---|
| Document | MA-SEM-0041, revision 01; lot SEM-41-3J7 |
| Main peak retention time | 10.20 minutes |
| Purity method | MA-UHPLC-031 / UV 214 |
| Main-component area purity | 99.18% |
| Reporting threshold | 0.05% |
| Separate content result | 9.98 mg per vial |
These are transcribed report details, not an independent analysis. Peak height is not peak area. Retention time belongs to the stated method and reference; 10.20 minutes is decimal minutes, not a minutes-and-seconds notation.Semax report (PDF) (opens in a new tab)Agilent LC handbook (opens in a new tab)
Check what the trace can distinguish
A smooth peak can contain more than one unresolved component. A plotted trace alone cannot establish complete separation or structural identity. Read the identity result separately and ask how the method distinguishes relevant alternatives.ICH analytical selectivity (opens in a new tab)Agilent LC handbook (opens in a new tab)
HPLC, UHPLC and UPLC are analytical platform or method descriptions, not sample quality grades. In the cited manufacturer comparison, the column and conditions were held constant to examine differences between systems. For your report, ask what separation was demonstrated; a newer platform name alone does not establish purity or explain a difference between results.Koshel, Birdsall and Yu — LC platform performance with a preserved peptide method (opens in a new tab)Agilent LC handbook (opens in a new tab)
UV response depends on wavelength and chemical structure, so a percentage obtained at one wavelength is not automatically interchangeable with another. Cropped axes, normalised displays and omitted small peaks can also change the visual impression without changing the underlying sample. Use the full report and its integration notes.Agilent LC handbook (opens in a new tab)
Do not multiply the vial label by area purity to infer measured content. Water, counterions and other constituents may require separate measurements; use the report’s assay and its calculation basis.Bachem analytical guide (opens in a new tab)
Sources and further detail
- Bachem — Quality control of amino acids and peptides (opens in a new tab)
Area-purity and content distinctions; not evidence about a particular supplier's analytical performance.
- Agilent — The LC handbook (opens in a new tab)
Detector discussion around printed pages 24–27 and method-development sections. Used for separation/detection dependence, not a laboratory protocol.
- ICH — Q2(R2): Validation of analytical procedures (opens in a new tab)
Section 3.1 and glossary on specificity/selectivity. Used for the question of analytical discrimination, not verification of a Novum method.
- Supplied Semax 10 mg certificate (opens in a new tab)
MA-SEM-0041, revision 01; task DMAS3J7; lot SEM-41-3J7. Source of the example, figures and document-specific observations. The cited PDF was re-read on 3 October 2026 to check this transcription; its issuer and findings were not independently authenticated.
- Koshel, Birdsall and Yu — LC platform performance with a preserved peptide method (opens in a new tab)
Manufacturer application note 720006275: defined LC platforms compared with the same column and conditions. No universal platform ranking is inferred.
Revised from the existing source dossier on 3 October 2026. Supplied-report values are document transcriptions, not independent authentication or new measurements. Source notes identify the scope of each reference; this article has not undergone independent scientific peer review.