Storage of buffers used for HPLC

[penxx]

Hi all! I am using ammonium acetate buffer (0.01M) as one of my mobile phases in HPLC and citrate buffers [1) 0.5M, 2) 0.005M at pH 2.5 and 3) a mixture of 70% 0.1M citrate/30% MEOH] for SPE of my samples. Am wondering if there is a need to refrigerate all the aforementioned buffer solutions to prevent microbial growth? If so, what is the recommended/safe storage period? (I've seen online recommendations ranging from 1 week to 6 months...) I also believe the it should be quite safe to store my elution solution that contains MeOH at ambient? Would greatly appreciate any advice/tips from those experienced with using buffers in HPLC! Thank you in advance!

[TylerSmith123]

Hi Penxx,

Nice to talk to you again haha. From reading your buffers, I would say all of the buffers that have been greatly acidified (like the pH 2.5) should resist almost all normal bacterial growth. The same goes for the solutions with 30% MeOH. The first citrate buffer you may want to make a concentrated solution that you always keep in the fridge, and make careful dilutions whenever you need to use it. If that solution is around a normal pH ~7, then I believe it will be the most vulnerable to bacterial growth. The ammonium acetate buffered mobile phase will also be vulnerable, and, if you can, the best and freshest strategy would be making fresh mobile phase every day (if the buffered solution is around pH 7.0/suitable for bacterial growth). It also depends on how frequently you open/use your different solutions, and adding a small amount of organic to your aqueous phases would help prevent bacterial growth as well.

[lmh]

my vote would be to trust the buffers with methanol in them, but make the 100% aqueous things fresh (or keep in the fridge for a couple of days at most). I have great respect for the ability of life to appear in, and thrive in, apparently sterile bottles.

[penxx]

Hi Penxx,

Nice to talk to you again haha. From reading your buffers, I would say all of the buffers that have been greatly acidified (like the pH 2.5) should resist almost all normal bacterial growth. The same goes for the solutions with 30% MeOH. The first citrate buffer you may want to make a concentrated solution that you always keep in the fridge, and make careful dilutions whenever you need to use it. If that solution is around a normal pH ~7, then I believe it will be the most vulnerable to bacterial growth. The ammonium acetate buffered mobile phase will also be vulnerable, and, if you can, the best and freshest strategy would be making fresh mobile phase every day (if the buffered solution is around pH 7.0/suitable for bacterial growth). It also depends on how frequently you open/use your different solutions, and adding a small amount of organic to your aqueous phases would help prevent bacterial growth as well.

Hey there again, Tyler! Thanks so much for the tips!

[penxx]

my vote would be to trust the buffers with methanol in them, but make the 100% aqueous things fresh (or keep in the fridge for a couple of days at most). I have great respect for the ability of life to appear in, and thrive in, apparently sterile bottles.

Hi lmh, thanks for sharing!