Top tips for the maintenance of pH Meters

Discussion in 'Supporting Chemistry' started by GeorgetheScienceTech, Apr 29, 2019.

  1. You will all be aware how important it is for pH meters to be accurate for BTEC, A-Level and beyond work for example determining an Acid Dissociation Constant. Firstly never store the probes in distilled or deionised water - use tap water. Secondly never touch the glass probe or it will be depolorised and always make sure that there is no bacterial groth on the probe by immersing in methanol for a few minutes. Thirdly allow the probes to sit in 3 M KCl for 30 minutes (especially for Silver-Silver electrodes. Next check the response by placing the probe in 0.1M HCl for 5 minutes then place in 0.1M NaOH for 5 minutes - the response should be fast. Finally calibrate the probes in accurately prepared pH4.00 and pH 7.00 buffers (place in pH 7.00 buffer first), check the speed of response and store in pH7.00 buffer until required (change the buffer every 5 days if the probes are frequently used, if not store dry). Good luck.:);)

    maintaining pH probes-2.png
     
    AllantheTech, MaddyT, 007 and 3 others like this.
  2. Cool thanks for that George.
     
    GeorgetheScienceTech likes this.
  3. that looks lovely George, thanks for sharing
     
  4. Thanks mate, and you're so right it is cool. I decided to create this thread on account of the problems other Memberes have endured with these pH Checkers- whether allowing Students to calibrate them (and goose them in the process) and the slow response over time due to Microbial films etc. I hope that my methods will be of help to others.:);) No hidden meaning in the wink PrepAdmain @prepAdmin :D:D:D
     
  5. Thank you from me too George.

    I was surprised they need to be stored dry for long term storage. This just goes to show an old dog can learn new tricks.
     
  6. @GeorgetheScienceTech I was wondering about the reasoning behind using tap water and storing dry, would it be possible to enlighten me?

    Also the methanol tip is ace!
     
  7. mine have a sponge in the cap (the £100 ones) and say to store them with the sponge damp? and others expensive probes i have used in a previous life have said store in pH4 buffer.
     
  8. Enlighten you I will Hugh @Hugh The Hanna type pH probes are sent out dry. Being dry (assuming that they have been cleaned) means that there will be no microbial film formed which means that the response time of the probe will be as it should be. If stored in pH 7 buffer for extended periods a microbial film will form so it is well worth cleaning them and storing them until required. These probes are only required for a few required practicals per year. Before they are used it will be necessary to soak them in Tap water for several hours to "condition them" then place them in pH 7 Buffer. Silver-Silver electrodes must never be allowed to dry out and must be maintained in 3M KCl.:);)
     
    Last edited: May 1, 2019
    Hugh likes this.
  9. If you use them with foods like milk etc you can also soak them in a protease to clean them.
     
    GeorgetheScienceTech likes this.
  10. A very good suggestion Paul.:);)
     
  11. I have pHed a load of milk in my time...
     
    GeorgetheScienceTech likes this.
  12. I found one of our pH probes today to have muddy water where the storage solution should be. (No idea how long they've been like that, but they we new a year ago and I calibrated them.) Any advice on trying to save it, other than rinsing lots in distilled water? Cheers
     
  13. Much improved method George. Previously I always had one or two that just would calibrate as well as I wanted. :)