Checking someone else's arithmetic: a worked example thread

Post #14 answers the question as asked. The question underneath it is different.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

Stating my assumptions rather than smuggling them in.

On post #12 — agreed on the reasoning, with one qualification.

Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.

The right answer here may simply be that it has not been measured.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

Helpful, and easy to find again, which is half of what a good reply is.

Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

This is where my knowledge stops and I would rather mark the edge than blur it.

On post #17 — agreed on the reasoning, with one qualification.

Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.

Post #21 answers the question as asked. The question underneath it is different.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

A 10 mg vial reconstituted three different ways: 1 mL diluent gives 10 mg/mL, 2 mL gives 5 mg/mL, 4 mL gives roughly 2.5 mg/mL. The arithmetic is the same; the concentration determines which syringe graduations are legible.

This is the sort of exchange that makes the archive worth searching.

Worth separating two things that post #21 runs together.

Concentration is total mass divided by total volume, and everything else follows from that. Ten milligrams into two millilitres is five milligrams per millilitre, and it does not matter how the vial was labelled before you added anything.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

Worth reading the earlier posts in this thread before acting on mine.

Do not shake. Swirl, or leave it. Vigorous agitation introduces air and shear, and neither helps a peptide go into solution any faster than patience does.

That is one dataset and I would not build a rule on it.

Preservative effectiveness is tested against a defined microbial challenge under defined conditions. It is not a licence to treat an entered vial as sterile indefinitely, and no supplier claims otherwise.

The answer changed when I changed how I was measuring, which was informative.

Understood. Thank you for being specific about the limits of it.

Worked example, since the arithmetic is the whole question. Five milligrams into one millilitre is 5 mg/mL. A 0.25 mg dose is 0.05 mL, which is five units on a U-100 syringe. Check that against your own numbers rather than taking mine.

That holds under the stated conditions and I have stated them.