rekonditioning
when rekondition is reqired due to electrode aging(see helpful operation techniqes , part 9), the following chemical treatments can be tried . they are presented in the order of the severity of their attack on the PH glass and may not improve (and in some case actually further deteriorate)electrode performance

1) immerse the electrode tip in 0,1 N HCL for 15 second , rinse in tap water.
repeat this sequence three times and then recheck the electrode performance . if performance has not been restored , try step 2.

immerse the tip in a 20% solution of NA4F.HF(amonium bifloride) for 2-3 minutes, rinse in tap water and recheeck performance

3)
immerse electrode tip in 5% HF for 10-15 seconds , rinse well in tap water , qickly rinse in 5N HCL .rinse well in tap water and recheck performanse . if performance has not been restored it is time to get anoter epoxy body , sealed referense combination pH electrode
ha srivet vad der stod i manualen , hoppas att nogon förstår det
mvh janne