What is a certificate of analysis, and what does HPLC actually tell you?

This is the single most misunderstood point, and the one most often exploited. A certificate of analysis applies to one specific lot of material, produced at one time, tested on one date. It says nothing about the next lot.

So when a supplier shows a single certificate on a product page and leaves it there for two years, that certificate is describing material that sold out long ago. The correct question is never 'do you have a COA', it is 'where is the COA for the batch number on the vial you are about to send me'.

High-performance liquid chromatography pushes a dissolved sample through a column packed with a stationary phase. Different compounds move through at different speeds, so they arrive at the detector at different times and appear as separate peaks.

The area under each peak is proportional to how much of that compound is present. Purity is the area of the main peak as a percentage of the total area of all peaks. When a supplier says 99% purity, that is what the number means: 99% of the detected material was one compound.

The trace itself matters more than the number. A clean chromatogram shows one dominant peak and a flat baseline. Several substantial peaks mean several substantial compounds, whatever the headline figure says.

HPLC does not identify anything. It separates and quantifies, but it cannot tell you what the peak actually is.

This is why purity alone is not worth much. A chromatogram can show a beautifully pure sample of entirely the wrong compound, and it will look identical to a beautifully pure sample of the right one. The trace would be flawless. The vial would still be wrong.

Mass spectrometry ionises the sample and measures the mass-to-charge ratio of the fragments, which gives the molecular weight of the compound present.

Because every peptide has a known theoretical molecular weight determined by its sequence, a measured mass that matches the theoretical mass to within a small tolerance confirms the compound is what the label claims. That is identity.

Purity plus identity is the pair. Together they say: this is the right compound, and this is how much of the vial is actually it. Either one alone leaves the important question open.

Check the batch number on the certificate matches the batch number printed on the vial. If it does not, the certificate is describing different material.

Check the date of analysis. A certificate from three years ago is a historical document.

Check the testing laboratory is named, and is not the supplier. In-house testing is a supplier grading their own homework.

Check both methods are present. Purity by HPLC, identity by mass spectrometry. If only purity appears, you know the purity of an unidentified compound.

Look at the chromatogram, not just the number. One dominant peak, flat baseline.

Is the certificate published before purchase, or supplied after it? A supplier confident in their material publishes first.

Is it addressable at a permanent URL, or emailed on request? Anything sent on request can be sent selectively.

Is the purity figure stated on every batch, or on 'select batches'? That phrase is doing a lot of work in this market.

Every MYOGENX batch certificate is public at a permanent URL before the batch is listed, and that URL is printed on the vial label.