for work I have to establish a recipe for preparation of a 1 M citrate-phosphate buffer pH 7.4, which should be composed of Na2HPO4 and citric acid. Both ingredients should be at sufficiently high concentrations to allow for preparation of the 1M solution at a final volume of approx. 50 to 200 mL. However, I am unfortunately not familiar with buffer calculations for chemistry. Also, on the web I have only found recipes for diluted versions of this buffer, that is also known as McIlvaine buffer and I am aware that there exist other buffer systems which are more suitable for buffering at a pH of 7.4. Please can you help me and propose me a recipe for a 1 M McIlvaine buffer pH 7.4 ? Many thanks in advance!