Simultaneous Kinetic Spectrophotometric Determination of Ascorbic Acid and Cysteine with an Optical Probe by Mean Centering of Ratio Kinetic Profiles Method A.B. Vishnikin*†‡, Yu.V. Miekh†, Ya.R. Bazel‡, M.E.A. Al-Shwaiyat§, G.O. Petrushina§§
	* Corresponding authors † State Research Institute for Laboratory Diagnostics and Veterinary and Sanitary Expertise, 30, Donetska st., Kyiv, 02000 Ukraine; *e-mail: vishnikin@hotmail.com ‡ Department of Analytical Chemistry, Faculty of Science, P.J. Šafarik University, Košice, 01454, Slovak Republic;  § Department of Basic and Applied Science, Zarka University College, Al-Balqa Applied University, Zarka St. 30, Al-Salt, 19117, Jordan; §§Dnipro State Agrarian and Economic University, Sergii Yefremov str., 25, Dnipro, 49600, Ukraine.
	Methods Objects Chem. Anal., 2019, 14(3), p. 163-170 https://doi.org/10.17721/moca.2019.163-170
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Abstract

A procedure for simultaneous kinetic analysis of a binary mixture of ascorbic acid (Asc) and cysteine (Cys) was developed using the method of mean centering of ratio kinetic profiles. The method is based on the difference in the rate of reactions of Asc and Cys with the complex of iron(III) with o-phenanthroline at pH 7.05. The use of an optical probe simplifies the carrying out of kinetic measurements, allows to obtain highly reproducible (S_r=0.01-0.02) results, and significantly reduces the time of analysis. The method of mean centering of ratio kinetic profiles is superior to the H-Point standard addition method, since it does not require such a long measurement time and there is no restriction on the constancy of absorbance of one of the components. Asc and Cys can be determined in the concentration range from 1 to 10 mg/L. The method was successfully used to determine Asc and Cys in dietary supplements.

Keywords: spectrophotometry, optical probe, method of mean centering of ratio kinetic profiles, ascorbic acid, cysteine

Article language: Ukr