Every lot from Pepti ships with a batch Certificate of Analysis that reports the HPLC purity result and the mass-spectrometry identity result under a lot code printed on the vial, the carton and the certificate. This page explains what each result proves, what it does not, and how to compare a lot with the public records at peptioem.com/coa.
The Certificate of Analysis is the one document every lot carries. It is issued by Pepti's QC for a specific lot code and reports the results measured on that lot. It is not a generic product sheet, and it is not reused across lots: a new lot gets a new certificate with its own results and dates.
The certificate carries the product or sequence name, the fill per vial, the lot code, the manufacturing date, the test date, the retest date, the HPLC purity result, the MS molecular-weight result and a conclusion against the specification. For a custom sequence the specification is your confirmed sheet; for a catalogue compound it is the factory's standard specification for that product and fill.
Everything else on this page is about reading those fields correctly, which is also what the receiving checklist walks through at the bench.
Identifies the lot. Printed on the vial label, the kit carton and the certificate. Match all three on receipt.
The catalogue product name, or the custom sequence name as written on the confirmed specification.
Nominal peptide quantity per vial as specified.
Manufacturing date, test date and retest date.
Chromatographic purity of the lot, as a percentage.
Observed molecular weight, to be compared with the theoretical value for the sequence.
Whether the lot meets the specification it was made against.
Analytical reversed-phase HPLC separates the main peptide peak from other species that absorb at the same wavelength. The purity figure is the area of the main peak as a percentage of all peak areas in the run. A higher figure means a smaller share of other UV-absorbing species; it says nothing about species that do not absorb, such as water, counter-ions or salts, and nothing about how much material is in the vial.
Two consequences for a buyer. First, HPLC purity and fill quantity are different questions: a lot can be very pure and still be under-filled, and a certificate that reports purity does not by itself report quantity. If fill quantity matters to your project, ask for it in the specification. Second, purity figures from different laboratories are comparable only when the method is similar; a lot tested by a third party under a different gradient can legitimately show a slightly different number.
For reference, published HPLC purity results across the public COA library of catalogue lots fall between 98.4% and 99.8% as of the last review date on this page. A custom lot is reported against its own specification; the range tells you what the factory routinely achieves, not what your lot will show.
HPLC answers
HPLC does not answer
Mass spectrometry measures the molecular weight of the main species and compares it with the theoretical molecular weight calculated from the sequence. A match within the instrument's tolerance shows that the main peak has the mass expected for the ordered sequence. For a custom lot this is the single most important check: it confirms that the peptide in the vial is the one you specified and not a deletion or a truncation with a similar retention time.
MS confirms mass, not sequence order. Two peptides with the same residues in a different order have the same mass, so MS cannot distinguish them; sequence order is controlled by the synthesis itself and by the identity of the starting materials. A buyer who needs sequence confirmation beyond mass should say so in the specification so the appropriate method can be discussed at feasibility.
On the certificate, compare the observed value with the theoretical value you calculated from your own sequence before ordering. If you did not calculate it, do so on receipt; it is the simplest independent check available and needs no laboratory.
MS answers
MS does not answer
The lot code is what ties the vial to the paperwork. Pepti prints the same code on the vial label, on the kit carton and on the certificate. On receipt, read the three codes against each other before anything else: a certificate that does not match the vial in hand is not evidence for that vial. For private-label orders the lot code is also marked on the approved proof, so the position on your artwork is known in advance.
| Where | What to read | Mismatch means |
|---|---|---|
| Vial label | Lot code, product or sequence name, fill | Wrong lot shipped, or label error; stop and raise it with the sales desk. |
| Kit carton | Lot code, kit count | Repacked or mixed shipment; check every kit. |
| Certificate | Lot code, product, fill, dates, results | Wrong certificate sent; ask for the certificate for the lot code on the vial. |
| Packing list | Kit count, vials per kit, cartons | Short shipment or miscount; reconcile before signing for the delivery. |
Pepti publishes certificates for catalogue lots at peptioem.com/coa. Each record names the product, the fill, the lot code, the manufacturing and retest dates and the HPLC and MS results, with a presentation copy of the certificate. The library is the factory's own record, maintained by Pepti, and it is the reference set for this site.
For a private-label buyer the library is a way to see how lots of the compound you intend to brand have been documented before you order, and to compare your lot's certificate with earlier ones after it arrives. For a custom-sequence buyer the library shows the certificate format and the purity the factory routinely reports, even though your sequence will not appear in it.
Not every catalogue product has a public record at every fill, and a record is not the same as a current lot; the certificate that matters for your order is the one issued for your lot code.
Using the library
Buyers are welcome to send vials from any lot to a laboratory of their choosing for HPLC and MS. A documented lot makes that comparison meaningful: the independent result can be read against the lot certificate rather than against nothing. When comparing, expect small differences in purity between laboratories that use different gradients or columns, and expect the MS result to agree on mass. If an independent result disagrees materially with the certificate, send both to the sales desk with the lot code; confirmed quality issues on a lot are handled under the order terms.
Pepti does not name specific third-party laboratories on this site and does not claim results that it has not measured itself.
Scope statement
Pepti does not present itself as a cGMP drug-substance (API) manufacturer or CDMO and does not publish a GMP certificate or DMF. Peptides on this site are supplied for research use by qualified B2B buyers. For research use only. Not for human or veterinary use.
A batch certificate reports measured chromatographic purity and molecular-weight identity. It does not prove fill quantity unless quantity was measured and reported, does not report microbial status, and does not establish suitability for any use. The research-use statement on every label and certificate is not a formality: Pepti supplies peptides to qualified B2B buyers for research use and gives no dosing or protocol advice.
Lot code, product or sequence name, fill per vial, manufacturing date, test date, retest date, the HPLC purity result as a percentage, the MS molecular-weight result and a conclusion against the specification. One certificate per lot, never reused across lots.
No. HPLC purity is the main peak's share of UV-absorbing species in the run. It does not measure quantity, water or salt content. If fill quantity matters, write it into the specification so it is measured and reported.
MS confirms that the main species has the mass expected for the sequence, which rules out deletions and truncations. It does not confirm residue order, because peptides with the same residues in a different order have the same mass. Calculate the theoretical molecular weight from your sequence and compare it with the observed value on the certificate.
At peptioem.com/coa, the public COA library maintained by Pepti for catalogue lots. Published HPLC purity across the library is 98.4%–99.8% as of the last review date on this page. A custom lot's certificate is issued for its own lot code and is not published there.
Yes. Send vials to a laboratory of your choosing and compare the result with the lot certificate. Small purity differences between laboratories are normal; the MS mass should agree. Material disagreements go to the sales desk with the lot code.
No. It is a research-use batch certificate issued by Pepti's QC. Pepti does not present itself as a cGMP drug-substance (API) manufacturer or CDMO and does not publish a GMP certificate or DMF.
Open WhatsApp with a pre-filled Pepti-RFQ message, or email the same details. A quote needs the compound or sequence, fill per vial, vial count, labelling and the document set you require.