Short answer
A compound identity file is a single record that ties one batch of a research peptide to its expected identity, the supplier's analytical evidence, your own measurements and the decision you made about it. It should contain the product and batch codes, the expected formula and mass from a public reference, the COA values, any in-house results, the storage record and an accept or reject decision with a date.
Key facts
- The file is organised around one stable batch identifier that appears on the vial, the COA and the internal record.
- Expected values should come from an independent public source such as PubChem, not from the supplier's own page.
- The measured intact mass is compared with the expected mass in the same units, monoisotopic or average.
- Mismatches, deviations and decisions are written down with a date and a name.
- The file is kept for as long as the material or data derived from it are in use.
Section 1: what was ordered
Record the product name and SKU exactly as listed by the supplier, the strength per vial, the number of vials, the order reference and the date. Add the compound name in the form used by public databases, so that it can be matched to a reference record. For a blend, list every component and its amount. This section answers the question: what did we think we were buying?
Section 2: what arrived
On receipt record the date, the condition of the shipping package, the labels on the vial (name, strength, batch), the appearance of the powder and the seal. Photograph the labels. Compare the batch code on the vial with the batch code on the COA and write down whether they match. Any discrepancy is logged immediately and the material is set aside until it has been resolved with the supplier.
Section 3: the expected identity
Write the molecular formula, the monoisotopic mass, the average mass and the sequence or structure from an independent public reference, with its source and the date on which it was read. For peptides, record the terminal groups, any D-amino acids or non-standard residues, and the salt form that the supplier states.
The compound pages on this site list the formula and masses together with the PubChem record, and the guide on average and monoisotopic mass explains which number to use.
Section 4: the supplier's analytical evidence
Copy the key values from the COA: the issuing laboratory, the report number, the test date, the methods (HPLC conditions, mass spectrometer type), the measured mass, the HPLC purity with the detection wavelength, the water content, the net peptide content and the counter-ion. Mark which values are given and which are missing. Record whether the report can be verified with the issuing laboratory.
Section 5: your own results
If you measure the material yourself, record the method, the instrument, the sample preparation, the measured intact mass, and the difference to the expected mass in daltons. Note any additional peaks and the mass shifts that you assigned to them, for example +15.995 for an oxidised form. Keep the raw data files and give them names that include the batch code.
Section 6: storage record and disposition
Write down where and under what conditions the material is kept, when it was opened, and any excursions from the intended storage. Finally, record the decision: accepted, accepted with a deviation, or rejected, with the reason, the date and the name of the person who decided. This is what makes the file useful to someone who reads it a year later.
A worked example line for BPC-157
Expected: C62H98N16O22, monoisotopic 1418.704, average 1419.54, sequence GEPPPGKPADDAGLV, free N-terminus and free acid, per PubChem. Measured by LC-MS: [M+H]+ at 1419.711, which matches the expected 1419.711. HPLC: one main peak at 98.3 % (214 nm). Counter-ion: acetate, net peptide content 82 % from amino acid analysis. Decision: accepted.
The numbers in this example are illustrative; the point is that each statement is paired with a source.
Frequently asked questions
Do I need to do my own mass spectrometry on every batch?
That depends on how critical the material is. At a minimum, the identity file should hold the supplier's evidence and your assessment of it. For critical work, an independent intact-mass measurement is the most informative single test.
What should I do if the measured mass does not match?
Check the units and the isotope convention first, then look for adducts and common mass shifts. If the difference remains, log a deviation, contact the supplier with the data, and do not use the batch for critical work until it is resolved.
Which public source should I use for expected values?
PubChem is a convenient source of formulas and masses. For compounds that are not listed, use the structure given in the primary literature and write the source in the file.
Primary references
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