PBS is commonly used for many purposed in the labs, most of the time it is freshly prepared but what in case it is made and kept for longer time. How long can it be stored and how to access its stability?
Dear Snapwill
PBS is a simple solution of salt and phoshate and it is very stable for long time also al room temperature.
When it is sterile and close can be stored for years.
The possible contaminations ( not only chemical but also biological) during it's use or preparation are the only factors that may reduce its time life.
Sterility is one of this factor that may alter stability so to improve its time life if you prepare PBS by your self life is it better filter at 0.22 or sterilize by autoclave (120C - 20 minutes ) and if you open the solution in a not sterile environment try to use maximun with in 1-2 months and only for experiments that not require sterility.
if you would like to test its properties you can assess the ph ( that as to be 7.2) by ph-meter and sterility by plating a small volume in tsb-agar plates. However for the most of the asssay if it do now show any variation in the colour ( eh. turbidity) it is a sign that it is still good.
ciao
Manuele
Hello, shelf life for PBS products are about 1 year at 20^C no chemical reaction would undergo in PBS and pH should remain stable as least energetic state has already been reached. If you see any changes in transparency or your PBS solutions become turbid, it should be discarded.
Good luck!
PBS is a stable buffer not like for example Tris buffer which you have to check as it undergo changing in its pH with the time.
If you see any growth in it ( any particulate suspend in it ) that means you should discard it. Generally it is is very stable especially if you keep it in the refrigerator ( at low degree ) in a clean close bottle.& to be in the safe side you can check its pH before use.
Thank you everyone for the answers.
Special thank you to Manuele Martinelli for details.
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