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Calculate the true active peptide content in a vial by accounting for purity, counterion/salt form, water content, and residual solvent from Certificate of Analysis (COA) values.
The total weight of peptide powder in the vial (label amount)
From the Certificate of Analysis (HPLC purity percentage)
Typical acetate salt correction (~13% counter-ion)
From Karl Fischer titration on the COA (typically 2-8%)
Residual solvent percentage from COA, if available (e.g. ACN, TFA, DMF)
from 10.00 mg gross vial weight
Visual breakdown of how each correction factor reduces the peptide amount from gross weight to net active content.
| Salt Form | Correction Factor | Counter-Ion Weight | Notes |
|---|---|---|---|
| Free base | 1.00 | 0% | No counter-ion present |
| HCl | 0.92 | ~8% | Common for small peptides; range 0.90-0.95 |
| Acetate | 0.87 | ~13% | Very common; range 0.85-0.90 |
| Citrate | 0.85 | ~15% | Less common; range 0.82-0.88 |
| TFA | 0.75 | ~25% | Largest correction; range 0.70-0.80; common from HPLC purification |
Actual correction factors vary by peptide size and number of basic residues. These are typical average values. For precise work, calculate from the molecular weight of the free-base peptide and its salt form.
A vial labeled "10 mg" rarely contains 10 mg of active peptide. The label weight reflects the total gross powder weight, which includes not just the peptide itself, but also counter-ions from the salt form, residual moisture, and trace solvents from manufacturing.
In practice, a "10 mg" vial typically contains only 7-9 mg of actual active peptide. This discrepancy matters for accurate dosing -- if you calculate doses based on the label weight alone, you may be under-dosing by 10-30%.
High-quality COAs report all of these values, allowing you to calculate the true peptide content. Vendors who only report purity without salt form or water content leave significant uncertainty in the actual amount of active peptide you receive.
Educational purposes only
This calculator is provided for educational and informational purposes only. It does not constitute medical advice. Salt form correction factors are approximate averages and vary by peptide. Always consult a qualified professional and verify calculations independently.