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Peptide Content vs Mass Purity: The Distinction That Matters
This is where most researchers accept incomplete information without realizing it. HPLC purity measures what percentage of the sample is peptide material. But it doesn't confirm how much of that peptide material is functional tesamorelin versus truncated seque
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- This is where most researchers accept incomplete information without realizing it. HPLC purity measures what percentage of the sample is peptide material. But it doesn't confirm how much of that peptide material is functional tesamorelin versus truncated sequences or misfolded variants. Peptide content assays. Amino acid analysis (AAA), quantitative NMR, or total nitrogen determination. Quantify the actual amount of correctly sequenced peptide per milligram of powder.
- A vial labeled '10mg tesamorelin, 98% HPLC purity' could contain 9.8mg of peptide material, but only 8.5mg of that might be correctly sequenced tesamorelin if peptide content is 87%. The difference. 1.3mg. Is sequence-related impurities that HPLC counted as 'peptide' but aren't biologically active. High-quality suppliers report both metrics separately on the COA. If you see only 'purity by HPLC' without a peptide content assay result, you're flying blind on functional dose accuracy.
- The peptide content assay typically appears as 'peptide content: 92.3%' or 'net peptide: 91.8%' on the COA. This number should be ≥90% for research-grade tesamorelin. Anything below 85% suggests poor synthesis control or degradation during storage. When calculating dosing for protocols, use the peptide content value. Not the HPLC purity. To determine how much active compound you're reconstituting. A 10mg vial at 92% peptide content contains 9.2mg functional tesamorelin; dose calculations based on 10mg will be 8% high.