METHODS AND OBJECTS OF CHEMICAL ANALYSIS ISSN title: "Metody i obʺekty himičeskogo analiza" An international journal devoted to all aspects of Analytical chemistry ISSN 2413-6166 (Online), ISSN 1991-0290 (Print)
		Ukr | En

Computer program "SpectroCalc,H5A" for spectrophotometric determination of acid dissociation constants

O.R. Sovyn, I.O. Patsay

Львівський національний університет ім. І. Франка, хімічний факультет, вул. Кирила і Мефодія, 6, Львів, Україна, 79005, i_patsay@franko.lviv.ua

It has been elaborated computer program "SpectroCalc,H5A" for spectrophotometric determination of the acid dissociation constants from spectrophotmetric data in multiwavelength mode. The algorithm is based on iteration methods and regression analysis. Initial data for the program "SpectroCalc,H5A" are spectra of the investigated substance's solutions under different pH values. Besides values of acid dissociation constants program calculates their confidence intervals (pKa±ΔpKa), spectra of all species (ε–λ) and standard deviation of absorbance (s) which describes the correspondence between experimental and calculated spectra. The program is applicable for investigation of monoprotic and  polyprotic substances, up to H5A. It has been demonstrated that the program is able to determine pKa values with high accuracy even if the absorption spectra of the species are very similar. correctness of elaborated algorithm is confirmed by mathematically simulated data and real dyes: methylthymol blue, xylenol orange, arsenazo III, chrome azurol S, eriochrome cyanine R, pyrocatechin violet. The pKa values obtained agree well with those derived from other authors and methods.