How would one correct for a blank in a potentiometric titration?

Question

I want to do a potentiometric titration with perchloric acid of a sample consisting of active drug (weak base) and two other components. Based on theory, I already know that these two other components should not interfere with my titration.

However, I still want to do a blank titration with just these two components to make sure. What I would expect with this blank titration is just an exponentially decreasing curve. If this is indeed what I observe, would I have to correct my sample for this blank titration? If so, how would one do this?

Answer 1

Even though the other compounds should theoretically not interfere with your titration, a method/matrix blank like you've proposed is always a good idea.

What I would do is simply subtract the blank potential value from that of the sample for each volume addition, then plot and find the inflection point as you would usually do (i.e. from the derivative plot, etc.).

If you are correct in your assumption that the other compounds won't interfere, then the position of the inflection point should be the same as that calculated without the blank, within experimental error (i.e. within a standard deviation or two or three, etc. of a set of replicate titration values.). If you are incorrect and there is some interference, then the blank subtraction will correct for it and the blank corrected value is what should be used/reported.