u/aurel_boateng

the tendon claims are the most repeated and the least evidenced

Agreed — cheap to make is a double-edged fact and it explains a lot about this corner of the market.

Nothing on this board is medical advice, and the people answering you — including me — are members with spreadsheets rather than clinicians.

Asked JEEP what volume they reconstitute to for their own stability testing and they answered in one line. Useful thing to know.

Wrote the date on the vial as well as the concentration after losing track of which one was opened first.

That is area percent from a certificate, not the amount of peptide in the vial. Two different numbers and a very common mix-up.

ask the dumb question, three other people are searching for it

Slight disagreement with this bit only, because a beginner reading it might take it as a plan rather than a description.

Pen or vial?

a COA is a certificate of analysis, the lab document for a batch

10mg into 3mL is 3.33mg/mL, and 2.5mg of that is 75 units

Are you accounting for the powder volume, or is that where the confusion is?

Are the related substances itemised or is it a single total?

post the whole document, not the headline number

Water content 3.8%, acetate 6.2%, purity 99%, net peptide about 90% of label weight. All four numbers honest, and I had to read it twice.

Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.

Show the arithmetic — where did the unit figure come from?

Right, and the arithmetic behind it: 5mg in 2mL is 2.5mg/mL, so 1mg is 40 units.

dilara_szabo has the units point exactly right.

Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.

the lot on the vial has to match the lot on the page

Nothing on this board is medical advice, and the people answering you — including me — are members with spreadsheets rather than clinicians.

The arithmetic in full: concentration is mass over volume, so 10mg into 2mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2mg is 2 divided by 5 millilitres, which is 40 units.

Short peptides in solution are subject to hydrolysis and, depending on sequence, oxidation. Storage state and time in solution are practical variables that this board almost never discusses.

Yes. Writing 2.5mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.

Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.

Careful — "the metadata looks odd" is a reason to ask a question, not a conclusion.

Agreed, and the practical version is: ask for the itemised table. If it exists, you get it.

This. Mass spectrometry for identity, not just an area percent, because a pure something-else is still something else.

Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.

My first question here was genuinely basic and it now shows up in search for other people asking it.

reconstituting at a round concentration makes every later dose easy

identity, quantity, stability — three separate questions

chromatogram or it did not happen

That is not what the method line says. It names the technique; it does not certify the operator.

Same view. Homopeptide prints the column and the gradient, which means somebody could actually reproduce the run.

Did the maths give you a whole number of units, or a fraction?

the related substances line is where the story is

Correcting myself upthread: I said the date was missing and it is on the second page, which I had not scrolled to.

How many mg in the vial and how many mL are you adding?