ABSTRACT
The chapter is devoted to quantitative analysis via the method. More specifically, it is quasi-exclusively devoted to Beer-Lambert’s law and its applications. Its establishment, its properties, limits and the analytical conditions of the measurements of absorbances are treated. Some applications are detailed. The law permits the qualitative and functional analysis, the identification of substances, the quantitative analysis and the standardization methods pertaining to the analysis of mixtures, the use of derivative spectrophotometry, the indirect mathematical methods of processing data and the determination of non-absorbent substances among which one finds the measurements of enzymatic activities via those of the reduced and oxidized forms of the cofactors NAD and NADP. Measurements by ultraviolet-visible spectroscopy also permit to check of the quality and purity of the pharmaceutical materials. Last but not least, the spectroscopy UV-visible permits the determination of a lot of thermodynamic constants, such as the pKa index values. Beer-Lambert’s law is particularly well adapted for these determinations.
