How may I prepare 100ml Tris-Urea Buffer for protein extraction?

From our lab protocols:

For 100 ml of your buffer you will need to weigh out dry urea (30.3 g) into a 250 ml beaker. Add 10 ml of 0.5 M Tris stock (at the pH you want), add 20 ml 10% SDS stock. Add a stir bar. Add distilled water slowly while stirring to dissolve all the urea, but do not exceed about 90 ml volume. The dissolution of urea is endothermic, so the solution will get cold. Do not heat it! Urea is not very heat stable and can form intermediates that react with proteins if heated. Let it dissolve at room temperature even if it takes a while. Check and adjust the pH of the solution if necessary (at 25 °C -- Tris buffer pH is temperature dependent!*). In a fume hood add 1 ml pure mercaptoethanol. Stir. Transfer the solution carefully to a 100 ml volumetric flask (a 100 ml graduated cylinder is probably okay for what you are doing, which does not require extreme accuracy). Rinse the beaker with a few ml of distilled water and add the rinse to the volumetric container. Make the volume up to the mark with distilled water. Transfer to a clean screw-cap container. Store at room temp and use within a week. For some applications, like FPLC, you will need to filter this (0.45 um or less) before use.

*Adjusting pH can introduce ions you don't want. Think about this before you do it. The alternative is to predetermine what the stock pH needs to be to give you the final diluted pH that you want by making some test solutions. Also, you can deliberately make your pH a little higher or lower than you want, so that your adjustment will be with something that is of no concern. e.g. if you want to avoid introducing sodium ions, make your pH a little high so that you will have to adjust it with e.g. HCl rather than e.g. NaOH.

I think this is actually what you want, but it should at least give you some idea of how to do it.