MEDUSA is a free chemical speciation software capable of depicting diagrams but it does not include organic compounds such as citrate which you need in your calculations.
For your purpose you can prefer Visual MINTEQ but please note that it cannot draw visual diagrams. Instead, software gives you the data for you to draw it in EXCEL.
very interesting topic. you can try it by ESI-MS but electrospray ionisation strictly is an method for analysing molecules in gas phase. If you have an experienced NMR operator maybe the best possibility would be NMR studies.
The third option that comes into my mind is UV/VIS or IR spectroscopy (both should work, UV/VIS probably better).
MEDUSA is a free chemical speciation software capable of depicting diagrams but it does not include organic compounds such as citrate which you need in your calculations.
For your purpose you can prefer Visual MINTEQ but please note that it cannot draw visual diagrams. Instead, software gives you the data for you to draw it in EXCEL.
Once you get familiar with Visual MINTEQ I think you will find it very easy to use. In addition to organic compounds, it gives you the ability to model closed or open systems, presence of specified solids, and the ability to add additional components.