As long as:

a) you have prepared a 40 mM phosphate buffer and

b) you have a H2O2 stock solution of known concentration

you can make a dilution of the H2O2 solution with the buffer.

For example, if you have the usually used H2O2 stock solution of 30% w/w concentration which corresponds to 9.8 M = 9800 mM, you can make appropriate (about 100 fold) dilution with the phosphate buffer in order to obtain a final concentration of 100 mM.

For a final volume of 10 mL, you need 102 μL of stock solution and about 9.9 mL of the buffer.

Depending on the final volume of the solution which you want to prepare, you can also make serial dilutions of the stock solution.

Thank you sir

Thank you sir this is very helpful

I have two follow up question -

1. can we reliably assume that the hydrogen peroxide stock will remain at 9.8M over time? are there ways to measure the exact molarity before diluting with phosphate buffer?

2. is it possible for the hydrogen peroxide to react with the phosphate buffer during mixing (e.g. by vortexing)?

thank you!

Dear Sindhushree

1. It is referred that the 9.8 M H2O2 solution stored in the dark at 2-8 oC, has retained full purity (by titration) for five years. (see link below)

Considering that the solvent of the 9.8 M solution is water, you can make a proper dilution with water in order to measure its absorbance. Then, if you have the suitable extinction coefficient for the used wavelength you can determine the molarity of the solution using the Lambert-Beer law.

2. I have not noticed any reaction between H2O2 and the phosphate buffer. Besides, it is referred that phosphorus-containing compounds stabilize the H2O2 solution. (see link below)

http://www.sigmaaldrich.com/content/dam/sigma-aldrich/docs/Sigma/Product_Information_Sheet/216763pis.pdf