Autosampler Problem - Precission

[John]

Maybe the salt in your aqueous MP or sample solvent is precipitating out in your IPA rinse. Suggest a rinse similar in organic composition to your MP (no solutes of course). We use 5% MeOH in water for all our systems.
JW

[syx]

I have made a conclusion:
Before we decide to choose washing/rinsing solution we must know the solubility of active substance(s) and components of diluent used (buffer).

[Mark Tracy]

If you really want to blame the autosampler, take it out and replace it temporarily with a manual injector. See if the problem persists.