Laemmli buffer - PH issues... (Nov/06/2007 )

I am sorry about the silly question, but maybe some of you had the same problem.
I have been making new Laemmli buffer, after all my old one was used up, and to my surprise, it is yellow.
It seems my SDS solution is about 1.5-2.0 pH (at least on the strip) while my colleague's SDS is around 3-4. I made a fresh one and it's the same.
Is my SDS powder expired or is it normal, I shouldn't bother and just add NaOH?
I wouldn't like to work on the SDS that is gone bad.

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Tris should keep it non-acidic; or did you use Tris-chloride?

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hi,
i wud not worry about SDS powder or solution. just adjust the pH.

sravan

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Yes, I use the standard formulation, with Tris-HCl 6.8, which worked before. It's just too much SDS to keep it buffered.
It's all fixed now, I used the fresh powder and it works.
Sravan - I guess I could do it, I think my old powder just accumulated water from the air. After all, the date IS expired (who cares about expiry dates anyway...if it works, it works). I wanted to be hyper sure, because it is a hyper important experiment though, and not for Laemmli buffer only, and who knows what really is that old powder.
Thanks all

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If the bromophenol blue still shows the blue color, not yellow, you are fine.

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