Formation Constants of Copper(II)-Salicylic Acid Complexes From Multi-Wavelength Spectrophotometric pH Titration Data Analyzed by Alternating Least Squares Including Newton-Raphson and Gauss-Newton Procedures

TCE

The Chemical Educator

ISSN: 1430-4171 (electronic version)

Table of Contents

Abstract Volume 12 Issue 1 (2007) pp 22-28

Formation Constants of Copper(II)–Salicylic Acid Complexes From Multi-Wavelength Spectrophotometric pH Titration Data Analyzed by Alternating Least Squares Including Newton–Raphson and Gauss–Newton Procedures

Gabriela A. Ibañez, Graciela M. Escandar, and Alejandro C. Olivieri*

Departamento de Química Analítica, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 531, Rosario (S2002LRK), Argentina, aolivier@fbioyf.unr.edu.ar
Received January 24, 2006. Accepted May 17, 2006.

Published online: 1 February 2007

Abstract. The use of a program written in the popular MATLAB environment is described for the analysis of multi-wavelength spectrophotometric pH titration data corresponding to the formation of complexes between copper (II) ions and salicylic acid in aqueous solution. The titration experiment is described in detail, as well as the program characteristics and operation. The analysis is completed with the estimation of the complex formation constants, the calculation of the distribution of species in solution at each pH point, the size of the spectral residuals in each experiment, and the error analysis of the estimated constants. The use of MATLAB allows for the resolution of this complex mathematical problem with very simple programming commands, which is of particular importance to popularize the introduction of advanced chemometric techniques in laboratory practices.

Key Words: Laboratories and Demonstrations; analytic chemistry; tritration; computers

(*) Corresponding author. (E-mail: aolivier@fbioyf.unr.edu.ar)

Article in PDF format (195 KB) HTML format

Supporting Materials:

Supporting material including the PkFit program and data is available in a Zip file for this article (18 KB).