peptiworks
Member
Since the lot-number thread went up, the most common question I get is a version of "is mine actually tested, or is the certificate from a different batch?" That is a fair question to ask about any vendor, including us, and there is a way to answer it in about a minute without asking anyone.
We publish the full lot list on the site, including the number that almost nobody prints: the measured fill weight. This is the part that keeps getting missed, so I will be blunt about it.
Purity and content are two different tests.
HPLC purity is an area percent. It tells you what share of the UV signal is your compound rather than related substances. It says nothing about how much material is in the vial. A vial can read 99.8% pure and contain 8 mg of a 10 mg label, because 8 mg of very pure peptide is still 8 mg. Every certificate that shows only a purity figure is showing you half the picture, and most of the market shows only that half.
The second test is the quantity assay: the lab weighs or titrates the actual peptide content and reports it in mg. That number is what your syringe maths depends on.
Why the second number matters more than the first.
If a vial is labelled 10 mg and measured at 11.5 mg, then anyone reconstituting to a known volume and drawing "10 mg worth" is getting 11.5 mg. If it measures 8.2 mg, they are getting 82% of what they think. Neither number appears on a purity certificate. This cuts both ways and I am not going to pretend it only cuts in our favour: overfill is not a gift, it is a dosing accuracy problem, and underfill is worse.
How to check a lot yourself, in three steps.
1. Get the lot code off the box or the vial crimp. It is usually a short alphanumeric string, something like TP260710, not a date.
2. Look that code up in our lot list at peptiworks.net/lot. It is open, no account, no email, no chat. If your code is not there, the certificate you were shown is not for that vial, and that is worth knowing before you inject anything.
3. On the certificate, read the line that says MEASURE or total quantity, next to the PURITY line. If there is no quantity line at all, the certificate is a purity certificate only.
The three questions worth asking any supplier.
Regardless of who you buy from, these three questions separate a real certificate from a decorated PDF:
1. Does it report a measured quantity in mg, in addition to purity?
2. Does the lot code on the certificate match the lot code printed on the box you received?
3. Is the certificate retrievable by lot code through a public lookup, so a stranger can verify it without a login?
A supplier who can answer all three is doing the testing. A supplier who only sends a screenshot of a chromatogram is asking you to trust the picture.
One thing I will not claim.
Measured fill is not the same as potency, and it does not tell you the peptide is sterile or free of endotoxin. Those are separate tests with separate certificates and we do not have them for every lot. I would rather say that plainly than let a fill-weight number imply more than it does.
If anyone has a lot code they cannot find a report for, from us or from anyone else, post the code and what the certificate shows and I will tell you what it does and does not prove. Not a pricing thread, so nothing for sale here.
We publish the full lot list on the site, including the number that almost nobody prints: the measured fill weight. This is the part that keeps getting missed, so I will be blunt about it.
Purity and content are two different tests.
HPLC purity is an area percent. It tells you what share of the UV signal is your compound rather than related substances. It says nothing about how much material is in the vial. A vial can read 99.8% pure and contain 8 mg of a 10 mg label, because 8 mg of very pure peptide is still 8 mg. Every certificate that shows only a purity figure is showing you half the picture, and most of the market shows only that half.
The second test is the quantity assay: the lab weighs or titrates the actual peptide content and reports it in mg. That number is what your syringe maths depends on.
Why the second number matters more than the first.
If a vial is labelled 10 mg and measured at 11.5 mg, then anyone reconstituting to a known volume and drawing "10 mg worth" is getting 11.5 mg. If it measures 8.2 mg, they are getting 82% of what they think. Neither number appears on a purity certificate. This cuts both ways and I am not going to pretend it only cuts in our favour: overfill is not a gift, it is a dosing accuracy problem, and underfill is worse.
How to check a lot yourself, in three steps.
1. Get the lot code off the box or the vial crimp. It is usually a short alphanumeric string, something like TP260710, not a date.
2. Look that code up in our lot list at peptiworks.net/lot. It is open, no account, no email, no chat. If your code is not there, the certificate you were shown is not for that vial, and that is worth knowing before you inject anything.
3. On the certificate, read the line that says MEASURE or total quantity, next to the PURITY line. If there is no quantity line at all, the certificate is a purity certificate only.
The three questions worth asking any supplier.
Regardless of who you buy from, these three questions separate a real certificate from a decorated PDF:
1. Does it report a measured quantity in mg, in addition to purity?
2. Does the lot code on the certificate match the lot code printed on the box you received?
3. Is the certificate retrievable by lot code through a public lookup, so a stranger can verify it without a login?
A supplier who can answer all three is doing the testing. A supplier who only sends a screenshot of a chromatogram is asking you to trust the picture.
One thing I will not claim.
Measured fill is not the same as potency, and it does not tell you the peptide is sterile or free of endotoxin. Those are separate tests with separate certificates and we do not have them for every lot. I would rather say that plainly than let a fill-weight number imply more than it does.
If anyone has a lot code they cannot find a report for, from us or from anyone else, post the code and what the certificate shows and I will tell you what it does and does not prove. Not a pricing thread, so nothing for sale here.