Nitrates Test kits and monitors!!!!!

[Johnny Reefer]

I love my PP NO3 monitor. Directions say to wait one minute, so that's what I do. Whatever the reading is at one minute is what I go with. How old are your calibration fluids? I've had my monitor for only a few months. During that time, I can't help but think that the cal fluids get cross contamination from each other. I plan to get new cal fluids at one years time, whether I need them or not.