Not sure why the calibration vials for the pH don't confirm the accuracy of the checker. One vial is sealed with a the "zero" fluid and a second with that fluid with the reagent. You run the check and read the checker's readout. I expected 8.0 from the calibration vial and that is exactly what the checker stated. The only issue could be if the reagent is off, no? As to procedure(s) being off, this is true for any test and tester. If you don't follow procedure your results won't be good.If you mean their pH checker HI 780, then just to clarify, like all Hanna checker calibration vials, the calibration kit does not confirm accuracy. It is not a true standard that you check the actual procedure.
It merely confirms proper operation of the electronics. If the reagents or procedures are off for any reason, the results can be inaccurate.