Auto-standardisation in spectrophotometry

Abstract

Poor precision has been obtained in the spectrophotometric determination of fluoride with a version of the alizarin fluorine blue method in which the total volumes of the solutions are small and relative variations in the final volume were substantial. In some analytical methods, this kind of situation can be ameliorated by means of internal standardisation, but the wide absorption bands typical of ultraviolet-visible light spectrophotometry render the technique impracticable for this application. However, the reagent itself can be used as an internal standard if absorbances are measured at an isosbestic point.