3 replies to this topic

[Haras911]

Can any one please help explain the calculations on how to make up the following;
lysis buffer (50mM Tris-Cl pH 8, 10mM EDTA, 2% SDS).
I'm totally lost on where to begin.

[bob1]

So what do you know about making up buffers?

If starting from powdered chemicals, you will need the following equations V=n/C (where V =volume, n=number of moles and C=concentration) and n=m/M_r (where n= number of moles, m= mass and M_r= molar mass).

Please read the Material safety data sheet (MSDS) before using any chemicals, and use appropriate safety equipment - if you don't have them, ASK FOR THEM!

EDTA is a bit tricky - you need the correct pH before it will dissolve.

[Haras911]

Only thing i know about making buffers is using Henderson Hasselback equation pH= pKa + log ( [A-] /[HA ) but just can't get my head around it.
Im guessing the 2% SDS is made up like this- 2g of SDS dissolved in 100ml of dH20.
I'm not even sure if thats correct and if its to be made up to a volume of 100ml. I'm really lost for this question no matter how hard i try i can't come up with a logic answer.

[mdfenko]

Haras911, on 05 October 2011 - 05:05 AM, said:

Only thing i know about making buffers is using Henderson Hasselback equation pH= pKa + log ( [A-] /[HA ) but just can't get my head around it.

you don't have to use the equation to make up a buffer. just have an appropriate acid and base component and use one to adjust the other to the desired pH.

Quote

Im guessing the 2% SDS is made up like this- 2g of SDS dissolved in 100ml of dH20.
I'm not even sure if thats correct and if its to be made up to a volume of 100ml.

it would be made up to 100ml.