Phenol shelf life - (Sep/11/2012 )

People say phenol goes bad, ie becomes oxidized
and that this oxidized phenol is damaging to dna and is thus unadvisable to use for dna (or rna) extraction.
Andy concrete data on shelf life (in a dark bottle, under tris, at 4oC)?

Folks say the color change is a reliable indicator of oxidation.
As for the color, people say pink is bad, but also "darker" or "reddish" yellow.
Anybody have any better input on these shades of yellow?
because isn't the new stuff a bit yellow too?

thanks in advance for responding to my (potentially silly) questions?

Nick R
microbial ecology
Sweden

yes, the new stuff we buy are also a bit yellowish. But when it is oxidized it turns orangish. We don't buy Phenol itself anymore, we buy ready-made phenol:Chloroform:IAA 25:24:1. That is not yellow.

Curtis on Thu Sep 13 10:09:36 2012 said:

phenol:Chloroform:IAA too becomes pinkish when old/may be oxidized. I did used pinkish/bad one for plasmid isolation. Got plasmid. digested too.

This ready-made mix also has the advantage that it is usually stabilised with 0.1 % 8-Hydroxyquinoline to avoid oxidation. No idea how much longer the shelf life is (we also had stabilised mix which was pink or yellow-red after some time).

Have used pinkish phenol with no problem. The new phenol we have is pure white.

We make out own phenol for DNA extraction.
Pure fenol - solid, self life.. don't know but pretty long.
Buffered phenol with hydroxyquinoline - yellow. Maximum fridge shelf life - 1 month. We don't use it if older than that (however if it's just few days off I probably used it few times without problem). I see no noticable color change after month. Pink phenol is bad, but I never seen it even on the old forgot leftovers. Probably the color depends on more things that just the age and oxidation. Recently we noticed that our newly made phenol is more orangish than it was, but works fine.