why does nobody talk about bacteriostatic water
why does nobody talk about bacteriostatic water. I would rather ask a basic question now than get this wrong quietly for two months.
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 contains benzyl alcohol as a preservative, which is what makes repeated entry into the same vial reasonable. Plain sterile water has no preservative.
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.
Tell me where this is wrong. That is the useful part of posting it.
best — the order this archive was captured in
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 concentration did you actually reconstitute at, rather than what did you intend to?
Agreed on the swirl. There is no reason to shake it and a good reason not to.
What concentration did you actually reconstitute at, rather than what did you intend to?
Adding one thing — put the date on the label too. Concentration plus date and you can never mix two vials up.
Careful — that arithmetic is wrong. 5mg in 2mL is 2.5mg/mL, so 1mg draws to 40 units, not what you wrote.
Show the arithmetic — where did the unit figure come from?
bacteriostatic water has the preservative, sterile water does not
a U-100 syringe reads 100 units to the millilitre, every time
write the concentration on the vial in marker, that is the whole post
Show the arithmetic — where did the unit figure come from?
Disagreeing with this line only: adding more water is not a safety margin, it is a different divisor.
Yes, and the dead-space point is worth repeating: it is small, it is real, and it is the same for every draw.
That is sterile water, not bacteriostatic. Same appearance, different product, and it matters for a multi-draw vial.
swirl, never shake
Pushback on the syringe advice: a U-100 barrel reads units of volume. Calling them "doses" is how the confusion starts.
The arithmetic in full: concentration is mass over volume, so 10mg into 3mL gives 3.33mg/mL. A U-100 syringe is graduated at 100 units per millilitre, so 0.5mg is 0.5 divided by 3.33 millilitres, which is 15 units.
The arithmetic in full: concentration is mass over volume, so 10mg into 3mL gives 3.33mg/mL.
This is the sentence that makes the rest unnecessary. Write it on the vial and the problem is gone.
Agreed — units are volume. Once that lands, the rest of the arithmetic is one division.
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