I'm trying to work through the calculations of a specific paper (linked here / below) but, my numbers are way off and I can't get them to match for the life of me. I need to make the same buffer but at a lower concentration. I'm not understanding how the paper was able to get the ratios (found in supplementary information) they used to make the buffer.
For example: 0.9M phosphate/citrate buffer, pH 3 Ratios used: disodium hydrogen phosphate (0.87g/100mL); trisodium citrate dihydrate buffer (3.51g/100mL)
How were they able to calculate those ratios? I've tried using Henderson-Hasselback equation but maybe I'm utilizing it incorrectly?