coa says 99% pure but the mass seems off, am i reading this wrong
ok so i think im confusing myself and hoping someone can just set me straight here. running a bpc stack for the achilles, been down this road before so im not new to this. ordered from a source ive used a couple times. coa came back 99.1% purity. solid number, no complaints. but when i actually look at the listed mass per vial i start doing the math and something feels off. the number of usable mgs feels lower than what im paying for. my first read was that 99.1% purity means 99.1% of the vial contents IS bpc-157. so if its a 5mg vial, i should have damn near 5mg of actual peptide. but then i started second-guessing myself, is the purity number saying something different? like is it possible to have super high purity but still have less actual mass than advertised? i know there's something about water content and lyophilization residue that might be eating into the real number but im not confident enough in that read to stake my protocol on it. can someone just explain the actual distinction here? purity vs mass, what each number actually tells you, and whether a 99%+ coa means anything about what's physically in the vial
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yeah this is the classic two-number problem. purity tells you the ratio, of whatever IS in the vial, what fraction is actually bpc-157. mass tells you the total amount. those are completely independent. so a vial could be 99% pure and only contain 4.2mg of peptide. the purity is still technically accurate. youre just getting less mass than labeled. vendors can hit both numbers honestly or screw up either one independently. when i do my cost-per-mg comparisons i always ask for both the HPLC result AND confirm the labeled mass matches what a decent lab would weigh out. purity alone tells you nothing about value. its half the equation. a 95% pure 5mg vial might actually be a better buy than a 99% pure 4mg vial depending on price.
purity from HPLC is a peak area ratio. the instrument has no idea how many milligrams you loaded onto the column, it just tells you that of what it detected, X% matched the bpc-157 retention time and fragmentation pattern (if theyre running MS alongside, which many dont). mass requires a separate measurement entirely. gravimetric before lyophilization, or quantitative HPLC with an external standard curve run at a known concentration. most COAs you see posted dont include that. they show you the chromatogram, you see a clean dominant peak at 99%, and you assume the vial is full. those are two different questions. if a vendor wont share method details (column, standard, gradient) i weight the COA accordingly.
purity = composition. mass = quantity. the coa purity number only describes the former. a highly pure but undermassed vial is entirely possible and not technically fraudulent if the vendor labeled the mass correctly and you just didnt check it against an independent weigh-in. the problem is most people only look at the purity line and assume it covers both. if youre skeptical, the move is to ask for the analytical weight or get a third party to verify mass alongside the purity. HPLC alone doesnt give you mass.
worth noting this specific issue, high purity, questionable mass, showed up with at least two batches from different vendors back in late 2022. purity was legitimate on the HPLC, nobody was disputing that. the problem was underfill on the lyo step, vials coming in measurably light. one of them corrected quietly, the other took about six months and a lot of public pressure to acknowledge it. point being this isnt a new confusion. and vendors who only publish purity without a mass verification step from a third party have always left this door open. not accusing anyone here, just saying the pattern isnt unusual.
this confused me too when i first started logging stuff. spent like week 3 of a protocol wondering why the response felt weaker than a previous run at the "same" dose. turns out i had switched vendors and the new coa was showing high purity on what was probably an undermassed vial. once i accounted for that and adjusted my pin count the numbers started making more sense, pain scale went from hovering around 5 back down to a 3 by week 5. could be placebo, could be the mass correction, honestly who knows. but yeah purity and mass are separate axes. you need both numbers to actually know what youre working with.