Does mazdutide adsorb measurably to the vial wall at 10 mg/mL?

Numbers first: mazdutide · 10 mg/mL.

I can do the algebra. I am not confident about the conversion factors.

If there is a standard way to lay this out, I would rather learn that than invent one.

What is the general form of this calculation?

10 mg/mL is 10000 µg/mL — roughly 1000 times the concentration at which surface adsorption is measurable. Losses to glass and plastic matter in the low microgram-per-millilitre range, where a monolayer on the wall is a real fraction of what is in solution. At 10 mg/mL that same monolayer is a rounding error. If you see an apparent loss at this concentration, suspect the dilution step or the assay before you suspect the wall.

The honest answer is that most reported "degradation" is adsorption and dilution error rather than chemistry.

Adsorption onto glass and plastic is significant at low concentrations — micrograms per millilitre — and negligible at milligrams per millilitre. It is the usual explanation for an apparent loss in a dilute preparation.

Hydrolysis cleaves the backbone, most readily at aspartate-proline and aspartate-glycine sequences, and is acid-catalysed. In a dry solid it barely proceeds at all.

At dilute concentrations, suspect adsorption before you suspect chemistry.

edited 16 Feb 2025 by RP_C18 — tightened the wording; no substantive change

The short version: water enables most of it, oxygen enables oxidation, surfaces enable adsorption, and agitation enables aggregation.

Freeze-thaw cycling drives aggregation through concentration at the ice interface and pH shifts as buffer components crystallise out at different rates. Each cycle costs something.

A mass spectrum resolves most of this: minus eighteen is dehydration or succinimide, plus one is deamidation, plus sixteen is oxidation, and an unchanged mass with a shifted retention time is an isomer.

The caveat is that none of these pathways can be seen by looking at a vial, and a clear solution can be substantially degraded.

Swirl, never shake. Aggregation is a handling problem more than a time problem.