Journal · Reading reports
Measured content versus the label: why the numbers differ
The label is what a vial should hold and the report is what the lab measured; filling, freeze-drying, water and the method cause small gaps.
Uses the lab reports of the 11 tested lots on this site
Key takeaways
- Content is a mass in milligrams, measured against a reference standard. Purity is a percentage.
- Small gaps come from filling, freeze-drying and the analytical method's own variation.
- Water taken up from the air lowers the peptide content of a powder.
The label is the amount the vial is meant to hold. The report is the amount the lab found. They are rarely identical.
Two numbers, two questions
Purity asks what share of the detected material is the peptide. Content asks how many milligrams of peptide are in the vial. Analytical tests for peptides rely on well-characterised reference standards, and HPLC is used for both content and impurities[1]. A vial can be 99% pure and still hold less than its label.
Why the numbers differ
Each step adds a little uncertainty. Vials are filled to a target within a tolerance. Freeze-drying is never fully even. And every analytical method has limits. Its accuracy is how close it comes to the true value; its precision is how much it varies between days, analysts and equipment[2].
Water matters too. Peptides are often hygroscopic, and water absorbed from the air can reduce stability and the overall peptide content of a powder[3].
The data on this site
Figure 1 sets the measured content against the label for each single-peptide lot: measured minus label, as a share of the label. 6 of the 8 lots measured at or above the label and 2 below it. The widest gap is M0TS-C at +11.4%, the closest 8PC-157 at -1.6%[4].
| Product | Measured content against the label |
|---|---|
| M0TS-CLot MC-823 | +11.4% |
| S3M4XLot SM-381 | +8.4% |
| T1RZ3P4T1D3Batch 2029/1 | +7.3% |
| R3T4Batch 2029/1 | +5.3% |
| S3L4NKLot SL-547 | +5.3% |
| 3P1TH4L0NLot EP-470 | +4.4% |
| 8PC-157Lot BP-482 | -1.6% |
| T3S4M0R3L1NLot TE-156 | -1.7% |
−20%label+20% |
Two cases that need a note
Blends. A vial with two peptides has two measured figures, each compared with its own label amount. 8PC Wolverine Stack measured 5.95 mg + 5.50 mg; C1C-1295 + 1P4M0R3L1N measured 4.69 mg + 4.54 mg.
6HK-CU. The lab measured the peptide part without the copper ("6HK-CU (6HK content)": 45.30 mg). So the figure is not set against the 50 mg on the label, which describes the whole compound.
How to use this
- Expect measured content close to the label, not equal to it.
- Be careful with a supplier whose measured content always equals the label to the digit, or who never shows it.
- Be equally careful with a large gap in either direction: it points to a problem with filling or with the method.
- Remember that content says nothing about purity. Read both.
Check it on real reports. The COA library has the full lab reports for 11 lots, with the original PDFs and links to the lab's own copies. Open the COA library
Sources
- McCarthy D, Han Y, Carrick K, Schmidt D, Workman W, Matejtschuk P, Duru C, Atouf F. Reference standards to support quality of synthetic peptide therapeutics. Pharmaceutical Research 2023;40(6):1317-1328. Open access. doi.org/10.1007/s11095-023-03493-1
- ICH. Q2(R2): Validation of analytical procedures. Final version, adopted 1 November 2023. Glossary: accuracy, intermediate precision, detection limit. database.ich.org (PDF)
- Bachem. Care and handling of peptides. Knowledge center, 23 January 2021. bachem.com/knowledge-center/care-and-handling-of-peptides
- Bali Peptide Supply. COA library: every lab report for the lots sold on this site. Reports issued by Janoshik Analytical, with their task numbers, keys and original PDFs. balipeptidesupply.com/coa/
Each source was read in its own document on 16 Oct 2026. Numbers about BP's lots come from the reports in the COA library.
How this article was made
Written by Bali Peptide Supply from the sources listed above, each read in its own document on 16 Oct 2026. Every number about our lots comes from the Janoshik Analytical reports in the COA library, read by the site build, not typed by hand. The lead photo is from Wikimedia Commons under a free licence.
BP sells research materials for laboratory use only. This article explains laboratory testing and lab reports. It is not medical advice and not instructions for use.
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