how to mix peptides step by step, and the two places it goes wrong
The mechanics, described not prescribed.
1. Let a cold vial come to room temp first. Adding liquid to cold powder can cause condensation and slows dissolving. 2. Wipe both stoppers with alcohol and let them dry. Wet alcohol doesn't do the job. 3. Draw up the intended volume of diluent. 4. Run it slowly down the inside wall of the vial instead of jetting it onto the powder. Peptides are shear sensitive and a direct stream is unnecessarily rough. 5. Let it dissolve. Swirl gently if needed. Do not shake. 6. Look at it. It should go clear.
Where it goes wrong, in order of how often I see it:
Shaking. Air liquid interfaces are where peptides unfold. Shaking makes a lot of them. Also foam, which makes accurate drawing harder.
Volume math. Concentration is set entirely by how much water you added. Get that wrong and every draw after inherits the error. This is where the ten-fold mistakes happen, not in the chemistry.
On cloudiness: a solution that stays cloudy or has visible bits after enough time hasn't dissolved fully or something's wrong. Clear is the expected end state for most of these.