I've never used the blog for this purpose, but why not?
The benchtop pH meter I purchased when starting the Pharmboy laboratory a number of years ago is beginning to have electronics problems (it's an old Fisher AccuMet of some sort with a digital display that reads in Roman numerals).
Hence, I am looking for recommendations for a new pH meter.
You would think this query for recommendations on the lowly pH meter is pedestrian and insignificant. But, I can assure you, that many a biochemical experiment has gone awry because the pH of one's solution is off due to inadequate attention to pH adjustment or calibration of the meter itself.
(I've even had an issue back when we used guanidine HCl for denaturing purification of insoluble recombinant proteins from E. coli; all of our enzyme assays stopped working suddenly...restriction digests, PCR reactions, etc. I noticed that someone had not been paying good attention to rinsing the pH electrode when making the guanidine solution and crystals of the protein denaturant could be found near the top of the electrode, probably feathering down gently into each and every solution made by each lab member).
Anyway, I kind of like the Hanna HI 4222 for its snazzy display and dual-channel pH and ion-specific electrode, but it's probably twice the price of a comparable Fisher or Thermo.
Any suggestions?
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I use an Orion 520A with a ROSS Ultra semi-micro electrode. Seems to do the trick for me, although in my case an automatic temperature compensator would be nice. I'm assuming all yours are done at a toasty 25?C (or at least constant T), so what do you care. Are you sure the crystals aren't KCl from the electrode filling solution?
I'm just going through this myself.
Are you just looking for the basics?
Orion 3 Star should do nicely.
Do you need to get the pH of tris buffers?
Try the Thermo Ross 81 line. They are supposed to be sensitive to tris, but without using mercury (so if you break it, you don't have to evacuate the room and call environmental safety to clean it up).
See "selecting the right pH electrode" at www.thermo.com
Also see
Get mercury out of your laboratory
(No, I don't work for Thermo Orion.)
Thanks, all - great advice also about how to stay away from a calomel electrode. I appreciate it!
I have been using the Magic XBM from company Gryf HB for years and it is really a nice piece of equipment. You will pay a litle more for their products but cant beat their precision and dependebility. This is the first company to develop a fully wireless laboratory measuring system using bluetooth technology. I am getting frustrated with the connector cables in my lab. so I will be purchasing their wireless system soon. As for outdoor use, I would recommend their Magic XBM system as it wont let you down.