Introduction

This chapter deals with classical volumetric titrimetry [1], In this collection of methods, the concentration of an analyte in a solution is determined by measuring the volume of a reagent of known concentration that is needed to react with that analyte. Traditionally, a reaction that goes to completion is required; for example,

The volume of the amount of reagent R (titrant) required to react with analyte A can be estimated by using an instrumental method to measure the concentration of A, R, or products (eq. (5.1)). A graph of these measurements vs. the volume of the titrant added to the solution is called a titration curve. Detection methods used involve measurements of pH, redox potential, conductivity, optical absorbance, and fluorescence.

In classical titrimetric analyses, the immediate goal is to find the endpoint volume of the reagent R as an estimate of the amount of R required to react completely with A. This allows an estimate of the amount of analyte A originally present in the sample, provided that the concentration of R is accurately known by a previous standardization.

In this chapter we shall see that some of the requirements of classical volumetric titrimetry are relaxed somewhat when nonlinear regression is used to analyze the data [2]. For example, the reagent R need not be accurately standardized, and the reaction need not go fully to completion at the endpoint. In fact, the endpoint of the titration need not even be determined. The concentration of A can be determined with high precision and accuracy directly from the titration curve. In the following sections, we provide a detailed example of nonlinear regression applied to the titration of a weak base with a strong acid. We then briefly discuss applications of the method to a variety of titrations employing different detection methods.

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