Our investigation, published in the October 2004 issue (1), confirmed that the food dye content of Kool-Aid can vary considerably between lot numbers. In the Stevens article (2), students use Kool-Aid samples to prepare calibration curves that are used to determine the concentration of dye in their unknown sample. Our article clearly shows a variability of percent by mass of food dyes in Kool-Aid samples between different lots. In order to quantify the concentration of food dye in Kool-Aid samples, calibration curves need to be prepared from pure food dyes of known molar absorptivity. In our investigation, the molar absorptivities of FD&C Blue 1, FD&C Yellow 5, and FD&C Red 40 were determined using certified samples obtained from the U.S. Food and Drug Administration. It is also troubling to see an educational journal publish a “connect-the-dots” calibration curve.

The Steven’s article also does not mention the mixture of food dyes found in many Kool-Aid flavors. The article reports data for Black Cherry (Red 40 and Blue 1) and Lemon–Lime (Yellow 5 and Blue 1), but never mentions that the measured absorbance is due to a mixture of food dyes. The article mentions “individual red and blue dyes in M&Ms”; however, our correspondence with the Mars Corporation indicates that all M&Ms contain multiple food dyes.

Finally, it is disappointing to see the similarity between the articles and yet no reference in the Steven’s article to our article (October 2006) that appeared in print a full two years prior (October 2004).

Literature Cited

1. Sigmann, S. B.; Wheeler, D. E. J. Chem. Educ. 2004, 81, 1475–1478.
2. Stevens, K. E. J. Chem. Educ. 2006, 83, 1544–1545.

See the author's reply.