pH Buffer Solutions

[DevinWolfe]

As many (most) of you already know I have access to NIST traceable pH calibration standards at no cost. Joel (Maclellan) brought up an interesting question at the last meeting with regard to them being exposed to air. I think this stems from our fresh water expereince as CO2 and pH are correlated when injecting CO2 for a planted tank.

His question had me thinking ALL day the last couple days. I knew that we left them open to air all day when working on multiple pieces of equipment but didn't know HOW taht was possible.

As it turns out the manufacturer uses different SALTS to create the pH balance required. This means that the only thing that will affect the pH value is temperature. Most pH meters also have temperature built in and compensate for the variance anyway, but it would be a good idea to double check the temp on the meter to the temp of the solution.

If anyone wants more specifics on the types of compounds used I got all that data from their tech department.

The main purpose of this post is to let you guys know that the solutions I have access to also contain an ANTIMICROBIAL agent. I'm sure you all know that this is not a good thing to introduce to any aquarium, so just be sure to rinse the probe following calibration with any solutions you get from me just to play it safe.

If anyone needs any let me know, post here or PM. pH 4.0, 7.0, and 10.0 - 150ml and 250ml bottles

 

[Engloid]

I absolutely MUST have the NIST traceability certs with the solution. Can you provide copies? I got really picky fish, and they really nitpick my paperwork.



Just kidding. I don't think I need anything. Thanks again for the calibration fluids. Oh, and after reading the instructions again, they said I only had to have the 7 and either 4 or 10. I figured I'd use the 10 since you said the 4 was bad about getting algae in it.

 

[DevinWolfe]

Well we do keep copies in case the EPA wants to see your documentation. They might revoke your permit if you don't have it readily available. How would you explain that to your Tangs???

 

[macclellan]

As many (most) of you already know I have access to NIST traceable pH calibration standards at no cost. Joel (Maclellan) brought up an interesting question at the last meeting with regard to them being exposed to air. I think this stems from our fresh water expereince as CO2 and pH are correlated when injecting CO2 for a planted tank.

Not exactly - co2 and pH are correlated period, it's just dramatic when injecting co2 in a planted tank. In reefs pH drops at night due to coral respiration (i.e. 'exhaling' co2) and lack of o2 production because there is no photosynthesis. It's just a fact about co2 and water, as I understand it. I raised the question because some guy on PT.net who worked at a water treatment plant with pH probes constantly insisted that the pH calibration standards available at LFSes were a waste of money, as they are off after being exposed to air (i.e. good for one use only). I don't know if those are the same salts as the NIST traceables or what; I assume not. I was just deferring to someone who seemed to know more than I about the subject, which you surely do too. I assume that the bulk solutions are as they are because the amount of co2 in solution is at equilibrium with the air? Dunno....

 

[DevinWolfe]

Not exactly - co2 and pH are correlated period

I guess I should have clarified that he told me that there isn't any *additional* CO2 in the solutions. Meaning that they have ~400 PPM (or w/e atmosphere is), so no amount of surface agitation or exposure to air could "degass" any CO2 to affect the pH.

I learned a LOT from talking with that guy today. Questions I really should have asked before instead of just accepting that "oh they just don't fluctuate because they're special." I did this for a couple years without even questioning it myself, so I'm glad you asked. It pushed me into finding out for myself!

 

[macclellan]

I believe equilibrium with the atmosphere is 4ppm. Target is 30ppm with co2 injection. Fish die around 50ppm or so.

I wonder if the packets have no co2 in the solution, and that explains why they change after exposure to air?

Anyways, I'd like some of your "special" solution at the next meeting, please!

 

[DevinWolfe]

I'll bring some for you and I'll have a couple extra sets with me at the meeting in case anyone else wants some that I don't hear from.