What a Peptide Specification Sheet Should Include Besides the COA

A certificate of analysis tells a researcher what one batch tested as: purity by HPLC, mass confirmation, and sometimes endotoxin or microbial results. A peptide specification sheet should include besides the COA a set of identity and handling details that the COA itself does not cover, because a COA describes a test result, not the product’s full profile. Without both documents together, a listing leaves gaps that make the product harder to evaluate or reproduce in a lab setting.

Why the COA alone is not a specification

A COA is batch-specific. It reports what one lot measured at the time of testing. It does not describe the peptide’s sequence, molecular formula, storage conditions, or packaging format, because those are properties of the product itself, not of a single test run. A specification sheet is meant to be stable across batches, while a COA changes every time a new lot is tested. Treating the two as interchangeable is a common gap in supplier listings, and it is one reason cross-checking a listing against its documentation matters before citing it as a source.

What a specification sheet typically covers

A complete specification sheet, read alongside the COA, generally documents:

• Sequence and molecular formula — the amino acid sequence or chemical structure the compound is built from, which confirms identity independent of any single test.
• Molecular weight — the calculated mass, which should be consistent with the mass spectrometry figure on the COA.
• CAS number, when one exists, for the compound as a reference point across suppliers.
• Form and appearance — lyophilized powder, color, and whether it is salt-free or supplied as an acetate or other salt form, since salt form affects the peptide’s actual mass.
• Storage conditions — temperature range for the lyophilized powder and for the reconstituted solution, and shelf-life guidance for each state.
• Packaging — vial size in milligrams, and whether the listed figure is net peptide content or gross powder weight including counter-ions and bulking agents.
• Solubility notes — the diluent the supplier used for their own testing, if stated, since solubility can vary with buffer choice.

None of these fields require a new test. They describe the compound as manufactured, which is why they belong on a specification sheet rather than a COA.

Net peptide content versus gross vial weight

This distinction is worth singling out because it changes any concentration math a researcher does later. A vial labeled 5 mg does not always mean 5 mg of the peptide chain itself. Salt forms, residual acetate, and moisture content can make up a meaningful share of the powder’s total mass. A specification sheet that states “net peptide content” as distinct from “gross weight” gives a researcher the figure to use in concentration calculations; a listing that only prints one number without labeling which one it is leaves that ambiguity unresolved.

For example, a listing states a vial contains 5 mg gross weight, with a specification sheet noting net peptide content of roughly 85% of that figure. The calculation for reconstitution concentration works from the net figure, not the gross one:

• Net peptide content: 5 mg × 0.85 = 4.25 mg
• Bacteriostatic water added: 2 mL
• Concentration = vial mg ÷ mL of diluent = 4.25 mg ÷ 2 mL = 2.125 mg/mL

If a researcher instead used the gross 5 mg figure, the same 2 mL of diluent would appear to yield 2.5 mg/mL, a difference of roughly 15%. A specification sheet that discloses net content lets that gap be accounted for rather than silently absorbed into the math. Tools like peptcalc.com can help recompute concentration once the net figure is known.

A comparison of what each document answers

Question	Answered by COA	Answered by specification sheet
What did this specific lot test at?	Yes	No
What is the compound’s sequence or formula?	No	Yes
Is the vial weight net or gross?	No	Yes (when disclosed)
What storage temperature applies?	No	Yes
Was mass spectrometry performed?	Yes	No
What diluent was used in-house for solubility testing?	No	Sometimes

How this affects listing evaluation

A listing that publishes a COA but no specification sheet gives a researcher a snapshot of one batch without the surrounding context needed to interpret it. Third party testing that includes both identity confirmation and batch-specific results, of the kind described at heezresearch.com/research/third-party-testing/, illustrates how the two document types complement rather than substitute for each other. When comparing suppliers, checking whether a specification sheet is published alongside the COA, and whether it states net versus gross vial content, is a reasonable way to judge how complete a listing actually is. Buyers who want a wider view of how different sellers format this information can compare listings across peer research-peptide catalogs, where documentation practices vary from vendor to vendor.

Summary

A COA verifies what one batch measured. A specification sheet documents the compound’s identity, form, and handling details that stay constant across batches. A listing that includes both, with vial weight clearly labeled as net or gross, gives a researcher enough information to evaluate the product and reproduce any concentration calculations accurately. A listing missing either document leaves part of that picture unverified.