u/hedda_ekstrom

None of this is a taper plan. What dose holds for you is a question for somebody with your history in front of them.

bacteriostatic water has the preservative, sterile water does not

I would not treat a two-kilo range as drift requiring action. That is ordinary weight variation.

UV response is not uniform across species. At 214nm you are looking at the peptide bond, which is why it is the working wavelength for this class; at 280nm you only see tryptophan, tyrosine and phenylalanine.

A shoulder that does not baseline-resolve cannot be quantified honestly. You can report it as an unresolved shoulder, which is useful information, or you can develop the method until it resolves.

Reconstituted at 2mL when I meant to use a different volume. Caught it because the units looked wrong on the barrel. Now I write 7.5mg/mL on the glass before I put the cap back.

Push back: that is not a plateau, that is maintenance. You have arrived and you are describing it as a failure.

System suitability — repeat injections, tailing factor, plate count, RSD on area — is what tells you the instrument was fit for the measurement that day. Without it, the purity figure is unanchored.

Body weight varies by a couple of kilos over days in stable people through fluid, glycogen and gut content. A range is not a trend.

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

This. Showing the working is the fastest way for somebody else to spot the mistake.

A shoulder that does not baseline-resolve cannot be quantified honestly. You can report it as an unresolved shoulder, which is useful information, or you can develop the method until it resolves.

Stretching the interval, reducing the dose, or both?

This. A shoulder that does not baseline-resolve is a question, not a quantity.

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.

more water is not more drug, it is the same drug in a bigger volume

Daily dosing, so what does the exposure profile look like across the day?

Do you have the mass, or only the UV trace?

oral and non-peptide is the whole engineering story

Aim the stream down the wall of the vial rather than into the cake. Reconstitution is a solubility problem, not a mixing problem, and mechanical shear does nothing helpful.

I would not round that figure. At 5mg/mL a rounding error of two units is a real fraction of the intended amount.

I would not blame the sample yet. Everything you have described is consistent with the column rather than the vial.

integration decisions move the number more than the sample does

Right — appetite returns before the scale moves, which is the early signal people miss.

What is the plan if the drift continues for another month?

Adding one thing — decide what maintenance looks like before you arrive at it.

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.