pH measuring equipment must be cleaned and calibrated regularly to ensure they are giving the user accurate readings. pH instruments are calibrated to pH7.0 first (buffer) then to pH4.0 (slope).
Bluelab's EC/CF equipment does not need calibrating as they are all factory calibrated here at Bluelab. The CF27.7 (EC2.77) solution is used as a reference or checking solution to ensure you have adequately cleaned the EC/CF probe.
Calibration Solutions should be stored in a cool place out of direct sun and heat. Please keep out of reach of children. They should be stored with the lids securely tightened. Not replacing the lid after use will result in evaporation which causes the salt content in the solution to rise decreasing the validity of the solution.