Determination of Coal Tar Concentration in Therapeutic Shampoo by Fluorescence Measurements of Perylene

Abstract

Determination of the concentration of the active component of a mixture is an important skill for the analytical chemist. However, complications arise when the sample of interest is a diverse formulation and the active ingredient itself is a multicomponent system. This experiment requires students to determine the concentration of coal tar in a therapeutic shampoo by measuring the fluorescence of perylene, one of the several thousand small-molecule components of coal tar. Students will use the standard addition method to achieve this, by producing a shampoo extract and spiking samples of this with a known amount of perylene. Additionally, by recording spectra of standard solutions of perylene, students will observe fluorescence self-quenching and discuss the mechanisms by which this occurs. Student feedback is presented and used to assess the effectiveness of this newly designed experiment, aimed at an advanced undergraduate analytical chemistry module.