u/saskia_mwangi

the powder cake sits at the bottom, the volume you add is the volume that counts

do the arithmetic before you reconstitute, not while holding a syringe

Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.

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

Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.

I would not round that figure. At 10mg/mL a rounding error of two units is a real fraction of the intended amount.

Correction: that gives 20 units, not what you have written. 5mg into 1mL is 5mg/mL and the division follows from there.

Proposed a rule change here with actual wording and it was adopted. That is the process working and it is not fast.

label the vial with the date as well as the concentration

Inter-lab variance on this assay runs roughly a point either way, driven mostly by gradient and integration. Two results inside that band agree; they do not disagree quietly.

Research-use-only material is not approved for human use, so treat everything in this thread as arithmetic about solutions rather than instructions for a person.

What is written on the vial right now?

The evidence standard on the vendor boards requires a document, a date or a named service behind any claim about a supplier. It is what makes those threads worth reading years later.

a result with no batch number is about a vial nobody can identify

label the vial with the date as well as the concentration

vendor, compound, batch, service, result — that is the template

That reading assumes area percent and net peptide content are the same number. They are not, and the report says which it is.

I keep a laminated card in the drawer with the arithmetic on it. Looks ridiculous. Has never once let me draw the wrong volume.

rule-change proposals need a concrete wording, not a complaint

The arithmetic in full: concentration is mass over volume, so 10mg into 1mL gives 10mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 2.5mg is 2.5 divided by 10 millilitres, which is 25 units.

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

Adding more water does not change how much peptide is in the vial. It changes the concentration, which changes the volume you draw for the same amount. That is the entire relationship.

if you are going to test, test the thing you actually received

Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.

Cosigning on saying who paid. It is the whole basis on which this log is worth anything.

A series across separate lots estimates a process. Repeat tests on one lot estimate the measurement. Both are useful and they answer different questions.

That only works if the fill weight is exactly the label weight, and it usually is not exactly anything.

That service reports area percent by default. Worth stating, since the thread has been comparing it to a mass figure.

The arithmetic in full: concentration is mass over volume, so 15mg into 3mL gives 5mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 1.5mg is 1.5 divided by 5 millilitres, which is 30 units.

Right, and a point or two between services is ordinary. It is agreement, and every month somebody posts it as a scandal.

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

What would the new rule do to the vendor evidence standard?

What was the claim on the certificate you are comparing against?

aim the stream at the glass wall, not at the cake

units are a volume on a U-100 syringe, not a dose

Inter-lab variance on this assay runs roughly a point either way, driven mostly by gradient and integration. Two results inside that band agree; they do not disagree quietly.

Started reconstituting everything to a round concentration and the six-in-the-morning error rate went to zero.

units are a volume on a U-100 syringe, not a dose

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