shelf life of PH calibration fluid

[Mimbler1]

Randy,
I purchased a pint each of ph7 and ph10 calibration fluids very inexpensively from a lab supply co. If I am careful not to contaminate them, and keep them well sealed between uses, would they have a shelf life problem I should keep in mind?
thanks, Mike

 

[rayjay]

I just renewed my pH7 and pH10 from Ricca Chemical, Texas.
The expiry date is on the bottle beside the lot number.

 

[steve the plumb]

I used the coralife brand once and I can tell you it sucked.I now use the american marine.Its in sealed packets.You can always try to calibtate with that and see if your solution is good.I paid $1.60 per packet.

 

[Randy Holmes-Farley]

The bottles can last a pretty long time, but especially the pH 10 can drop as CO2 enters it each time you open it. And as mentioned, some brands are just crappy to begin with.

if your meter allows you to enter the specific values for the calibration fluids, here's an idea:

Buy new pH 7 and 10 packets (1 each) from a good company (Pinpoint/American Marine, Milwaukee,Orion, etc). Then carefully calibrate your meter with them. Once done, check the pH of the bottles, and write the values on them. Say, 6.93 and 9.82. Then, use those values the next time you calibrate, and the bottles are probably good for another year then (if careful).

These articles have more info:

Measuring pH with a Meter
http://www.advancedaquarist.com/issues/feb2004/chem.htm

A Comparison of pH Calibration Buffers
http://reefkeeping.com/issues/2005-02/rhf/index.htm

 

[Mimbler1]

thanks Randy, and the others who replied. I do have a neptune that allows me to enter the calibration values so that is a good solution,
Mike

 

[Randy Holmes-Farley]

You're welcome.

Good luck.