LC-MS identity check for a peptide lot

LC-MS means liquid chromatography coupled to mass spectrometry. The chromatograph separates the sample, and the spectrometer reports a mass for a selected peak, often as a mass-to-charge ratio that the laboratory converts to an observed molecular mass. Laboratories compare that observed mass with the mass calculated from the amino-acid sequence, including common terminal modifications when the report states them. Agreement supports identity. It does not replace the area percent, and the area percent does not replace it.

A file that shows only a chromatogram is not an LC-MS identity package, even if the filename says MS. Open the PDF and find the mass. For the method note, see HPLC versus LC-MS. Third-party files linked from this catalogue are usually Janoshik reports tied to one lot.

Mass and chromatography answer different questions

LC-MS couples a liquid chromatograph to a mass spectrometer. The chromatograph separates the sample. The spectrometer reports a mass for a selected peak, often as a mass-to-charge ratio that the laboratory converts to an observed molecular mass. Laboratories compare that observed mass with the mass calculated from the amino-acid sequence, including a terminal amide or an acetyl group when the report states one. Agreement supports identity. It does not replace the area percent, and the area percent does not replace it. A file that shows only a chromatogram is not an LC-MS identity package, even if the filename says MS.

Salt form moves the mass. Trifluoroacetate and acetate are common counter-ions in synthetic peptides. If the report names the species that was weighed, copy that species. If it is silent, that conversion is not printed on the file. For the glossary lines, see TFA salt and acetate salt. Net peptide content is recorded only when the PDF states it.

Match the mass to one vial

The sample name, the date, and the task identifier have to match the glass in hand. BPC-157 10 mg, GHK-Cu 50 mg, and retatrutide are separate sequences with separate library anchors when those lots are published. A GHK-Cu mass includes the question of whether the report is the copper complex or the metal-free tripeptide. A retatrutide mass for a 10 mg fill does not document a 30 mg fill. TB-500 10 mg is a fragment nickname, not a mass. Until a TB-500-only report is published, a thymosin beta-4 textbook mass does not belong in the cell, and the 5 mg/5 mg blend mass does not belong there either.

Third-party files on this catalogue are usually Janoshik reports. The laboratory name is not the result. Open the PDF from the certificates library, not a photograph of it. For the method note, see HPLC versus LC-MS. For the document primer, see how to read a peptide COA.

What a matching mass does not do

A matching mass does not authorize human or veterinary use. It does not create a Drug Identification Number. It does not set a solvent volume. It does not survive a decant into an unlabelled tube: write the lot on the secondary container before the primary vial is closed again. Research use only. Domestic shipping, if you are receiving the vial, is Canada Post Xpresspost after Interac e-Transfer, as written in Canada laboratory procurement.

Adducts are a common reason a first glance at the spectrum looks "wrong" when the sequence is right. Sodium and potassium adducts, and a stated counter-ion, sit at different masses from the free peptide. If the report assigns the peak, copy that assignment. If it does not, leave the cell blank instead of picking the nearest integer. For the glossary lines for the spectrum and the calculated mass, see mass spectrum and molecular weight. Then file the vial under the storage note the same day the parcel arrives.