This program can be used to fit pKa values to pH dependent data where the data titrates from one value to another e.g. ppm data, absorbance data, fluorescence data, Ki and Km data etc.
The program fits and plots data to the equations:-
If one pKa only
Sobs=S1(1+K1/H)+S2/(1+H/K1)

If two pKa values
Sobs=(S1*H^2+S2*KA*H+S3*KA*KB)/(H^2+KA*H+KA*KB)

When "Fit " is selected you must input the initial estimates of ppm (S1 and S2 or S1,S2 and S3) and the pKa (PK1 or pK1 and PK2) values. The experimental data is then fitted using an iterative, non linear least-squares regression program. Note the two pKa fit is a five parameter fit and so it requires good data and good estimates to fit the data.
Results can be printed, saved as a text document or copied and pasted into other applications such as Word.
If you want to refresh your knowledge of the practical aspects of 1D NMR you might find the iphone app "NMRQA" on the iTunes app store useful.