What I have understood from your question is that you are making lysis buffer using mentioned components. .....

How much you are preparing in terms of volume? ( lets take 100 ml)

Prepare 90 ml of 20 mM Tris HCl and adjust the pH to 8.0. Then add EDTA solution (5 ml of 40 mM EDTA, concentrated) and TritonX 100 (2 ml of 50%, concentrated) to make final concentration (2 mM for EDTA and 1% for TritonX100). Now it is 97 ml of your buffer. Finally, add DW to make it 100 ml of your lysis buffer. Shake it or Vortex it and then use or store as per your protocol.

Remember its buffer solution and final pH should remain 8.0 even after addition of 2mM EDTA and 1% Triton X100 at their final concentrations.

Hello, your final solution pH needs to be 8.0

Dear Gabriel, you need to adjust pH of the final solution.

When the solution composition is written thus:

"20 mM Tris-HCl, pH 8.0 ; 2 mM EDTA; 1% Triton X-100,"

I interpret it to mean that the pH of the Tris buffer was 8.0, not that the pH of the complete solution was adjusted to 8.0. The pH may be different from 8.0 in the complete solution.

An additional ambiguity is that people often use concentrated buffer stock solutions to prepare their buffer solutions. For example, someone might dilute 1 M Tris-HCl pH 8.0 to 20 mM, and assume that the pH of the diluted solution will also be 8.0. For Tris, this is an incorrect assumption. The pH will be a little lower. You can't tell from the above statement whether a 20 mM Tris solution adjusted to pH 8.0 was used, or whether a concentrated Tris stock solution at pH 8.0 was diluted to 20 mM without pH adjustment.

The best practice would be to adjust the pH of the complete buffer, but if you decide to do this I suggest you add the Triton X-100 after adjusting the pH to 8.0. This is to avoid clogging your pH electrode with the detergent. Triton X-100 should not affect the pH.

In every case you have to adjust the pH of the final solution....