[Discussion] we are measuring mg/mL at the wrong time and calling it noise
Thinking out loud about this: we are measuring mg/mL at the wrong time and calling it noise.
If your calculation produces a fraction of a unit, the concentration is wrong for your dose. Change the water volume until the numbers land on whole units.
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.
Reconstituted at 2mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 15mg/mL on the glass before I put the cap back.
Would rather be corrected in public than confident in private.
best — the order this archive was captured in
The lyophilised cake displaces a small volume, so the true concentration is very slightly lower than the arithmetic suggests. It is a fraction of a percent and it is dwarfed by fill tolerance.
Yes. Writing 5mg/mL on the vial takes four seconds and removes the entire class of error this board exists to fix.
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.
bacteriostatic water has the preservative, sterile water does not
Not quite. Bacteriostatic and sterile water are not interchangeable for a multi-draw vial, and the difference is the preservative.
Yes.
gradient_goblin has the units point exactly right. They are a volume on the barrel and nothing else.
gradient_goblin has the units point exactly right.
Right, and the arithmetic behind it: 10mg in 2mL is 5mg/mL, so 0.25mg is 5 units.
Right — the volume you add is the only variable you control here, and the cake does not change it meaningfully.
Working has to be shown on arithmetic posts. Added a note asking for it rather than removing this one.
Agreed on the swirl. There is no reason to shake it and a good reason not to.
Why "more water" keeps confusing people, including me for a month.
The vial contains a fixed amount of peptide. Water changes nothing about that amount. What it changes is concentration, and concentration is the divisor between the dose you want and the volume you draw.
So doubling the water halves the concentration and doubles the units for the same dose. Nothing is diluted in any sense that matters; you are simply reading a bigger number off the same barrel. Pick the water volume that puts your usual dose on a whole number of units and life gets easier.
Cosigning the round-number approach. Reconstituting to something awkward is how you end up drawing 27.5 units at six in the morning.
if the maths gives you a fraction of a unit, change the concentration
Bacteriostatic or plain sterile water?
- 1The lyophilised cake displaces a small volume, so the true concentration is…8 comments in this branch · started by u/ilias_cabrera