Chemical Speciation: A Guide to Understand Titrimetric Analysis

Abstract

Chemical speciation modeling (equilibrium simulation program, MINTEQA2) was used to understand the chemistry behind titrimetric analysis and to monitor changes in experimental conditions in chemical titrations quickly and easily. Determination of magnesium and both magnesium and calcium in a mixture by EDTA titrations can be done at pH 10 in the presence of Eriochrom black T indicator. The end point is detected by the color change from red to blue. Simulation results of these titrations highlighted the fact that over the pH range 7-11, complexation of magnesium and calcium by EDTA is independent of pH while indicator speciation is highly dependent on pH. Thus the quantitative determination of magnesium and total magnesium and calcium by EDTA titrations using Eriochrom black T should be done at pH values of 9-10. By using computer simulation programs it is easy to calculate the chemical speciation at each step in a titration and to gain a better understanding of why a particular procedure does or does not work under particular experimental conditions.

Chemical Speciation Analysis of Sports Drinks by Acid–Base Titrimetry and Ion Chromatography: A Challenging Beverage Formulation Project

“…This lab has been used in a variety of formats for the past ten years. 1 We have had a number of students successfully analyze sports drinks and other beverages like Kool-Ade and Tang for potassium, sodium, sugars, food dyes, and volatile flavors as well as the analytes described in this project. Some alternative procedures we have used for determining analytes are included in the Table 1 notes.…”

“…Chemical speciation, a central theme in many undergraduate analytical chemistry classes, has been described in numerous articles dealing with theory and calculations. Theoretical approaches for calculating speciation include numerous commentaries on distribution (alpha) diagrams (1)(2)(3) and spreadsheet applications for acid-base titrations (4)(5)(6)(7)(8). However, there is a paucity of laboratory experiments to illustrate why speciation is important in real-world applications or how one determines the formulation of a commercial product in the laboratory.…”

Determination of protonation constants for 2-hydroxy-1-(2-hydroxy-4-sulpho-1-naphthylazo)-3-napthoic acid

“…Chemical speciation modelling has developed in recent years as an important tool for analytical chemists. It has been widely used to explain the behavior of metal ions in solutions (Duffield & Williams, 1989, Liyanage & Janaratna, 2002, Liyanage & Allas, 1999. In a similar fashion chemical speciation has played a critical role in the determination, correction and confirmation of thermodynamic formation constants J A Liyanage et al 48 De Robertis &et al, 1995, L-Gonzalez andet al, 1997).…”