Peptide purity usually means the percentage of the target peptide relative to peptide-related impurities as measured by HPLC, commonly at 214 nm where the peptide bond absorbs. It is a useful measure, but it does not mean that the sample consists entirely of dry target peptide by weight.
Peptide purity reflects the amount of the desired target peptide compared with peptide-related by-products such as deletion sequences, truncation sequences, incompletely deprotected peptides, and peptides modified by side reactions.
Water, residual salts, and counterions such as TFA are not represented in the HPLC purity percentage in the same way as peptide-related impurities. Even a highly purified peptide may still contain noncovalently bound water or salt-associated mass.
| Impurity type | Description |
|---|---|
| Deletion sequences | Shorter peptides lacking one or more amino acids from the target sequence |
| Truncation sequences | By-products arising from capped or prematurely terminated chains |
| Incompletely deprotected sequences | Peptides carrying residual protecting-group related features |
| Cleavage-modified sequences | Peptides altered during cleavage or handling chemistry |
| TFA-related material | Counterion-associated mass that is not the same as peptide-related purity |
A peptide can be high purity by HPLC and still contain water, TFA, or other non-peptide material. That is why purity and content should not be treated as identical.
If you are calculating assay concentrations, comparing batches, or planning a quantitative biological study, peptide purity alone is not always enough. Sequence difficulty, counterions, and net content can all affect the practical material in hand.
Analyze your sequence to better understand peptide behavior:
If you need help interpreting peptide purity for your application, please contact sales@lifetein.com or use our quotation form.