help with Hanna phosphate checker

[Magickiwi]

Originally Posted by lastlight

if that's the case and we can't assume that two seemingly identical vials are the same to the meter then perhaps even inserting the same vial back into it but rotating it differently could be a factor too.

Bingo... Which is why the Hanna colorimeters for phosphate get such bad reviews. They are a pretty flawed method if two different vials, etc. interfere with the reliable results. And having an auto-off of three minutes when simply mixing the reagent takes a minimum of two was just poor planning...