The association constant for colormetric complex 1:1 Ligand with metal measured in Uv-Vis spectroscopy
In general you need to know the spectra of both the free ligand and the complex. Then you can process the spectra arising from the spectrophotometric titration, to get the molar fractions of the ligand and complex, to calculate the binding constant in each solution and to estimate the standard deviation. It is a routine procedure, you can read about in the Perkampus UV-Vis spectroscopy book for instance. However if your binding constant is low and you are not able to obtain the pure spectrum of the complex in the process of spectrophotometric titration, there are two scenaria: a) the complex is blue shifted, then the ligand has a spectral range where it absorbs only; in this range you can calculate the molar fraction of the ligands and the fraction of the complex comes from iso-molarity; b) the complex is red shifted. in this case you must apply band decomposition or similar advanced data processing, which is pretty complicated and depends on the particular case.
Mr. Basseem,
By Benesi-Hildebrandt equation. Please pay attention to ref. 1.
[Ref. 1] H. Benesi, J. Hildebrandt, J. Am. Chem. Soc. 71 (1949) 2703.
Thank you for all, but I need to calculate the standard deviation for linear curve.
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