In this Activity, students examine the effect of pH on the intensity and color of the emission of fluorescent dyes in liquid laundry detergent. They perform two titrations using vinegar to estimate the pH at which the fluorescence properties change. In the second titration, sodium bicarbonate is added to buffer the detergent solution. This Activity illustrates the principles of UV-excited fluorescence, pH indicators, and the effect of buffers. It can also be used as a starting point for discussions of the environmental impact of consumer chemicals present in wastewater.
Richard B. Weinberg, J. Chem. Educ. 2007, 84, p800A.