This is an updated version of the SAIEUS_pK program earlier operated on the Excel VBA platform. SAIEUS_pK has been mentioned in a number of studies involving the surface acid-base properties.

This program calculates the **pK distribution of acid-base systems from the potentiometric titration data [1]**. The solution method of the integral equation was adopted from the earlier work on the surface energy distribution [2]. **The proton binding isotherm** derived from the potentiometric titration curve is used as data input to the program. The meaningful and stable results are obtained by employing a **regularization method combined with non-negativity constraints [3]**.

The program is operated **interactively**. It is equipped with several controls and diagnostic tools [4] that facilitate the user in selecting the optimal pK distribution as a solution for the analyzed data.

Titration data may be entered in a form of the proton binding isotherm, **Q (pH)**, or the titration curve **pH (V)**. The titration curve is converted to binding isotherm using the internal procedure based on the work of Contescu et al. [5].

**References**

[1] J. Jagiello, T. J. Bandosz, K. Putyera and J. A. Schwarz, J. Colloid and Interface Sci. (1995) 172, 341-346. Determination of Proton Affinity Distributions for Chemical Systems in Aqueous Environments Using Stable Numerical Solution of the Adsorption Integral Equation.

[2] J. Jagiello, Stable Numerical Solution of the Adsorption Integral Equation Using Splines. Langmuir (1994) 10, 2778-2785.

[3] C. L. Lawson and R. J. Hanson, Solving Least Squares Problems. Prentice-Hall, Englewood Cliffs, NJ, 1974.

[4] C. Hansen and D. P. O’Leary, The Use of the L-Curve in the Regularization of Discrete Ill-Posed Problems. Siam J. Sci. Comput. (1993) 14, 1487-1503.

[5] C. Contescu, J. Jagiello, and J. A. Schwarz, Heterogeneity of Proton Binding Sites at

the Oxide/ Solution Interface. Langmuir (1993) 9 , 1754-1765.