Sorry I haven’t been updating here much. I’ve had a lot of homework, even if some of it is art (I’ll try and post pictures of some of my projects some day). I had a class canceled this week, though; and to make-up the time, the professor gave of several options of activities we could do and then post a brief summary on the class discussion board. I chose the activity that we had planned to do in class that day: leaf chromatography! I’d been excited to do it in class and had already picked several leaves, and I’d wanted to do it with Sister and Munchkin at home, too. So, this is the results of my replacement option assignment as posted to the class.
Option E: Leaf Chromatography
#1 – Japanese Maple variety 1
#2 – Ornamental Plum
#3 – Japanese Maple variety 2 – back yard
#4 – Japanese Maple variety 2 – side yard
#5 – Maple
#6 – Apricot
– (6) Half Pint mason jars
– Pint mason jar
– 80% Isopropyl alcohol
– (3) Metal spoons
– Metal strainer
– Glass bowl
– Hot air blow dryer
– Coffee filters
– Paper towels
– Black light
– Assistants – Munchkin and Sister
First, I collected five or six leaves of the same color from each tree. The next day, with the aid of my assistants, we tore the leaves into small pieces, removing as much of the woody stem and leaves as possible, and put the pieces into the mason jars. We added just enough alcohol to the jars to cover the leaf pieces and then mashed them with the metal spoons, cleaning the spoons with paper towels between jars. We left the leaf mash mixtures to sit overnight, permitting the pigments to extract and the alcohol to begin evaporating. The next day, we strained the leaves using a metal tea strainer, transferring the liquor into a glass bowl and then decanting back into the original jars, and left the jars overnight to evaporate further. On day three, we forced further evaporation by agitating the mixtures and gently heating them with a blow dryer. Then we cut approximately 1” by 5” strips out of the coffee filters. The strips were placed in the mason jars with at most 0.5” in the pigment liquids and clipped to the top of the jars. The filter paper strips were left in the jars for about 90 minutes. We then removed the strips from the jars and clipped them to the outside of the pint mason jar to dry. When the strips were dry we examined them for color bands under both room lighting (LED) and black light.
Results and Discussion
Some of the leaves started releasing pigment immediately as we mashed them in the alcohol. The bright red leaves (#3) spread in the alcohol particularly quickly. Others, like the yellow apricot leaves (#6), were more difficult to both soften and to see pigment starting to stain the alcohol. Despite this, all off the mixtures developed clear bands of color on the filter paper. At approximately the same distance from the bottom of each strip except #6, there are thin lines of yellow and yellow-green. These should be from the chlorophyll remaining in the leaves. In the same area, there is also a slightly wider band of clear yellow, which shows on all of the strips, which is probably the xanthophylls. Further up in most of the strips is a wide, diffuse band of red, showing how far the anthocyanins travelled. Again, this color is missing on strip #6. The uppermost stain on each strip fluoresces brightly under black light. On strips 3, 5, and 6, this edge shows yellow-orange but is only slightly yellow on the other strips. The color is from carotenoids; but as this band of color coincides with the solvent line, the glow may be an artifact of the alcohol. On a related not, the liquors for leaves #2 and #4, which otherwise looked olive green, glowed red under the black light indicating that those two leaves probably had the most chlorophyll remaining in the leaves. They also had the clearest green and yellow-green bands.
“The Chemicals Behind the Colours of Autumn Leaves.” Compound Interest. September 2014. Accessed October 13, 2017. (http://www.compoundchem.com/2014/09/11/autumnleaves/)
“Chlorophyll Lab.” Cynti, Laura. C-Lab. December 2010. Accessed October 13, 2017. (http://c-lab.co.uk/experiments-details/chlorophyll-experiment.html)
“Find the Hidden Colors of Autumn Leaves.” Scientific American. October 2011. Accessed October 13, 2017. (https://www.scientificamerican.com/article/bring-science-home-leaf-colors/)
Honestly, even if it was for homework, I had a lot of fun. Of course, I got to do it with one person who is the target audience for the experiment and one person who is a professional chromatographer. I guess maybe I cheat a little.