We bought some fresh spinach to add to our salad for a healthy lunch, and saved a few of the leaves. We then chopped up the spinach leaves and soaked them in ethanol for an hour, to extract chlorophyll. By filtering the liquid and diluting it with distilled water, we had our chlorophyll sample. We ran two tests. The first test was similar to the food dye/mouthwash investigation; we measured adsorbance as a function of wavelength. The results are shown to the left. Note the little bump in the graph, just beyond 900 nm. We confirmed it to be caused by the ethanol in the sample.
One final test was done with the chlorophyll solution. Chlorophyll is fluorescent, and we wanted to see if the Vernier Spectrometer could detect it. To test fluorescence, which is light emission rather than absorbance, we removed the light source/cuvette holder from the spectrometer. Then we poured about 2 mL of the chlorophyll solution into a plastic cuvette with four clear sides. We sealed the cuvette with a plastic cap and placed it directly in front of the opening in the spectrometer. By positioning a pen light (also purchased at the grocery store) at a 90° angle to the spectrometer opening, we could not only see the faint orange-red glow of the fluorescing chlorophyll in the cuvette, but the Spectrometer detected it as well. The graph is shown here to the right.
The noisy graph can be attributed to a few factors: primarily that room lights were dimmed but not completely turned off, a plastic cuvette was used (for convenience), and the light source was a fairly wide-beamed white light. The important point here is that with grocery store items and non-quantitative sample preparation, we were able to successfully measure the absorbance spectrum and the fluorescence of chlorophyll.
We wished to continue our chlorophyll investigation, so we wandered along another aisle in the grocery store and selected a couple of types of olive oil. It turns out that part of the color of olive oil is due to chlorophyll. We tested two grades: extra virgin (purported to have the maximum amount of chlorophyll of all grades of olive oil since it is derived from the first pressing of the olives) and light (alleged to contain no chlorophyll). More testing is needed, but our initial results are shown here.
Note that while the olive oil graph has some qualitative similarities to the chlorophyll samples described previously, it is not an exact replication of the chlorophyll absorbance peaks.
Download Determination of Chlorophyll in Olive Oil (60.4 KB PDF)