Ph Calibration Powder Solution Storage

[NeonRabbit221B]

I wasn't able to find anything online about this besides that the powder packets for pH calibration are typically good for two years. How about once they are mixed? I stored them in old solution bottles and use about 100 ml in a graduated cylinder to calibrate but was wondering if the mixed solution is shelf stable.

 

[Doctorgori]

Sounds like you are oversees, Asia? I mention it because I’ve only seen those powder pH packets from China ... To me its too many variables that could go wrong mixing your own solution. No chance you can get Scientific American or Hanna liquid standards?

 

[NeonRabbit221B]

I actually do have other pre-mixed standards but dozens of the packets that have come with pH probes for reef-pi builds that I tend to hoard. The only reason I am asking is I recently bought a cheap pen type probe for my freshwater tanks and it only accepts the powder calibration values (6.86 ect).

 

[Randy Holmes-Farley]

Liquid pH buffers , especially high pH buffers like pH 9 or 10 or higher) can absorb CO2 from the air and may drop over time. that is a good reason for them to have a shelf life, even in a closed bottle.

I tested many here and found some old ones had declined in value:

A Comparison of pH Calibration Buffers by Randy Holmes-Farley - Reefkeeping.com

 

[NeonRabbit221B]

Liquid pH buffers , especially high pH buffers like pH 9 or 10 or higher) can absorb CO2 from the air and may drop over time. that is a good reason for them to have a shelf life, even in a closed bottle.

I tested many here and found some old ones had declined in value:

A Comparison of pH Calibration Buffers by Randy Holmes-Farley - Reefkeeping.com

Would the degradation of these buffers vary from a pre-mixed vs powder packets? Based on the article it seems that the powder buffers are wildly inaccurate. I guess from now on I will mix and use ASAP. Thanks Randy!

 

[Randy Holmes-Farley]

Would the degradation of these buffers vary from a pre-mixed vs powder packets? Based on the article it seems that the powder buffers are wildly inaccurate. I guess from now on I will mix and use ASAP. Thanks Randy!

Any "packet" listed in the article is a packet of liquid, not dry powder.

Dry powder will be more stable. The packaging is also important. Foil is good.