Story of 2 Active Substances in a Dosage Form

[HW Mueller]

You can probably minimize the dilution by adding a very small amount of concentrated buffering salt/solution and maybe some organic directly to the samples.

[syx]

I will compare the result I have got with the result of lowered buffer concentration of mobile phase (from 0.050M to 0.025M). The buffer for mixture of sample solution is also reduced to 0.05M.

Result:
Reduced buffer concentration in mobile phase reduced resolution.