UV-Vis

How Much Cranberry Juice is in Cranberry-Apple Juice?

Students determine the amount of cranberry juice (as a volume percent) in mixtures of cranberry juice and apple juice by measuring the absorption of mixtures and comparing to a calibration curve prepared for cranberry juice. The experiment assumes that the absorbance of apple juice is negligible at the analytical wavelength, which isn’t strictly true. The experiment can be modified easily by a simultaneous analysis at two or more wavelengths.

The full citation is here: Edionwe, E., Villarreal, J. R., Smith, K. C.  J. Chem. Educ. 2011, 88, 1410–1412 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed2002237

Have Biofuel, Will Travel: A Colorful Experiment and a Different Approach to Teach the Undergraduate Laboratory

This experiment describes a  quantitative UV-Vis analysis of mixtures of diesel/ethanol and diesel/biofuel based on the absorption of a solvochromatic probe dye. Students first synthesize the dye and then monitor the change in the dye’s λmax for different known mixtures, creating an empirical scale of solvent polarity. Mixtures containing unknown (to the student) mixtures of diesel/ethanol and diesel/biofuel are then analyzed using calibration curves of solvent polarity as a function of the concentration of ethanol or biofuel.

The full citation is here: El Seoud, O. A., Loffredo, C., Galgano, P. D., Sato, B. M., Reichardt, C.  J. Chem. Educ. 2011, 88, 1293–1297 and a link to the article is provided below (subscription to the journal required).

http://dx.doi.org/10.1021/ed1009464