I keep the mixture at 4°C and we usually buy 500ml.

Every month or every two month we need another bottle.

also after 2month the mixture looks good.

I would say yes you can do it for some month.

yes, I used to store it in 4 degrees and it was good for at least 3 months.

Yes you can store it for longer time in 4 degrees but preparing fresh solutions gives good results than using the stored ones.

Thank dear friends for your kind information ..

Sorry that I have some questions. I wonder that "What is the longest time for storage this mixture?" Can be a year or not? and Why?

we buy 500ml, at room temperature, and still good, for long term, you may store it at 4C

Yes, you can store it at 4 C for more than a year

Ya we can store this mixture up to 6 months in room temperature

Yes, surely, for 6 to 8 months...

Though this mixture remains stable for a long time, its extraction efficiency of genomic material deteriorates as time progresses.

As Jonathon mentioned, phenol should not be oxidized (once it is oxidized it turns to pink color) take care about that. Generally equilibrated phenol can store either at room temp or 4 C. You can store as long as you want provided it should not be oxidized.

The main problem is that phenol oxidises with age, and this can affect the quality and yield of you DNA. If you are going to make it fresh you will have to redistill it before adding the chloroform/isoamyl alchohol, but it is best to buy very pure solutions that are redistilled already- phenol is nasty and any reduction in manipulation is a good thing. Some people add 8-Hydroxyquinalone to the mix when it is being made, which acts as an anti-oxidant preventing phenol oxidation- this turns the solution yellow. I would not use the solution beyond 6 months as phenol goes pink then yellow when oxidised, and so you would not be able to tell if has oxidised or not with 8-Hydroxyquinalone in it. Store it carefully in brown glass wrapped in tinfoil at 4C. Jonathon makes a good point about buying it in the most appropriate quantities, if you only want to do a few mini-preps, don't buy 5 litres! it is a real hassle to dispose of correctly and safely!

Cannot be stored at room temperature for long .Store in brown giass bottle at 4 c for a year.