Ashley Mo

Upper school chemistry teacher Andrew Irvine assists Arturo Vilalta (10) with the paper chromatography lab. Students determined which M&M flavors contained yellow #5 using chromatography.

Honors Chemistry students conducted a paper chromatography lab using colored dye from M&Ms to determine which flavors contained the synthetic food dye Tartrazine, also known as “Yellow #5,” over the course of two class periods ending on Feb. 27. 

Students first labeled a sheet of Whatman paper, a type of filter paper, with six M&M colors: yellow, orange, red, green, brown and blue, as well as Yellow #5. They rubbed toothpicks dipped in distilled water on the shell of the M&Ms to remove the colored dye, which they then dotted onto the paper.

After the dots dried, students folded the paper into a cylindrical shape and developed their chromatograph in a 1% NaCl solution. As the solvent traveled up the paper, the colors in the dye separated, showing that brown dye contained red, orange, yellow and blue, while green dye had blue and yellow hues. 

Students divided the distance the dyes traveled by how far the solvent traveled to find a retention factor called the Rf value of each color. In order to identify which flavors contained Tartrazine, they compared each of the dyes’ Rf values to Yellow #5’s Rf value of 0.54.

Following the lab, students wrote a lab report and discussed their results. Most students found that the yellow, green and brown flavors contained Yellow #5, as they all had yellow dye with similar Rf values as Yellow #5. Honors Chemistry student Audrey Dagum (10) enjoyed how the lab was both interactive and educational.

“[The lab] was really creative, and I felt like it was very hands-on,” Audrey said. “We got to play with colors, and it almost took me back to elementary school arts and crafts while also being informational and related to chemistry.”

The paper chromatography lab not only aligns with Honors Chemistry’s current unit on intermolecular forces but also involves real-world applications. Through learning about the broader uses of chromatography in everyday life, students gained insights into the importance of chemistry in various fields.

“I want my students to know that chromatology exists and can be used in analytical, forensic and even medical situations,” upper school Honors Chemistry teacher Andrew Irvine said. “I also liked that we talked about food coloring and the origin of food coloring, especially because red dye [No. 3] was managed by the state of California.”