Mass spectrometry (MS)

Mass spectrometry (MS) is an analytical technique used to evaluate molecular mass by measuring mass-to-charge ratio. While HPLC measures purity (how much of one species there is), MS can add molecular-mass context for the species being reviewed. For peptides, the typical workflow uses electrospray ionization (ESI) or matrix-assisted laser desorption ionization (MALDI) to produce charged molecular ions, which are then separated and detected by a mass analyzer (quadrupole, time-of-flight, or orbitrap). The observed monoisotopic mass is compared to the theoretical mass calculated from the peptide sequence; a close match can support batch review when that test is available. Such testing can complement the HPLC purity number, but it should not be assumed for a batch unless the relevant CoA or lab record shows it. A peptide can be highly pure by HPLC while still requiring additional review for molecular identity if the research protocol depends on that distinction. For peptides with complex modifications - phosphorylation, biotinylation, fluorescent tags, cyclization - tandem MS (MS/MS) may be used to fragment the peptide and review sequence coverage. Peptra Labs only presents MS characterization for batches where that testing exists in the relevant record.