Mass Spectrometry: The Test That Proves What Is Actually in the Vial

A mass spectrometer ionises the sample and measures each ion's mass-to-charge ratio with high precision. Modern instrumentation resolves peptide masses to well within the difference a single amino-acid substitution would make, which is why the technique became the backbone of protein and peptide analysis generally.[1]

Every peptide has an exact theoretical molecular weight determined by its sequence: the sum of the residue masses less the water lost at each peptide bond, plus whatever modifications the molecule carries. BPC-157, a 15-residue sequence, comes out around 1419.5 g/mol. If the measured mass matches the theoretical mass within tolerance, the molecule is the one the label claims. If it does not, the purity figure is describing something else.

Amino Acid Sequence

• ·Substitution. A cheaper analogue, or a different peptide entirely, is invisible to a purity measurement and unmistakable on a mass measurement. The incentive is largest for expensive compounds and for very short sequences, where the cost gap between the labelled molecule and a substitute is widest.
• ·Variant confusion. N-acetylated against standard semax, CJC-1295 with the drug affinity complex against without: same families, different masses. Identity testing is what distinguishes them, and it is the only thing that does. The clearest case is set out in CJC-1295 with DAC vs without.
• ·Modification failures. An amidated C-terminus, an acetylated N-terminus or a lipid chain each shift the mass. A synthesis that failed to install one produces a molecule that is not the target, and again the chromatogram will look fine.
• ·Quantity. Quantitative mass-spectrometric methods measure how many milligrams the vial actually holds, which is the fill-accuracy figure that completes a certificate rather than an identity check as such.

Three things belong on it: the theoretical mass of the target compound, the found or observed mass measured in the sample, and agreement between them within a stated tolerance. A certificate that says "identity confirmed" without publishing either number has asked you to take the conclusion on trust while withholding the data.

The audit is quick. Take the compound's published molecular weight, compare it against the theoretical value printed on the certificate, and then compare the found mass against both. A supplier whose listed molecular weight does not match public chemistry databases is copying specifications it has not checked, which tells you something before you get to the certificate at all. The method is in peptide molecular weight.

Published Certificate

Select strength

10mg20mg40mg50mg

Batch

RETA-CA-26E-01

Purity (HPLC)

99.637%

Measured content

11.76 mglabelled 10 mg

Laboratory

Janoshik

Verify on the lab’s own databaseAll published certificates

HPLC purity, mass-spectrometric identity, measured content. Three figures, one lot, one named laboratory, and a verification key that resolves outside the supplier's own website.

The reason to insist on all three is that each is blind to what the others measure. Purity cannot see substitution. Identity cannot see a short fill. Measured content cannot see contamination. Together they are a description of the material; separately they are three different ways to be reassured about the wrong thing.

The scale of the problem is documented rather than theoretical: market surveillance of peptide products sold online without prescription has found products failing on content and on what they claimed to contain.[2] The answer to that is not a better adjective on a listing, it is a lot-linked certificate that a third party can confirm.

Available at Eppix Labs

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