The absorption spectras of the five different solutions all differ in max wavelengths and ranges of wavelengths. The blue food coloring had one peak with a max absorption of .1201 at 630.7nm. The 1:1 mix of blue and yellow food coloring had two peaks with a max absorption of .1911 at 421.1nm. The yellow food coloring has one peak with a max absorbance of .3734 at 422.9nm.
|Type of Solution||Color of Solution||lmax values|
|Blue Food Coloring||Blue||630.7 nm|
|Yellow Food Coloring||Yellow||422.9 nm|
|Mixture of Yellow and Blue Food Dye||Light Green||421.1 nm|
|Chlorophyll a Standard||Light Green||447.0 nm|
|Spinach Leaf Extract||Light Green||445.4 nm|
Chlorophyll A also had two peaks with a max absorbance of .05310 at 660.6 (red).
When the compound’s spectrum has more than one maximum wavelength, it indicates that the compound is able to absorb light at multiple wavelengths (colors). In the graph with the food coloring spectras, the 1:1 mix had a peak in the blue and yellow wavelength ranges of the spectra and a drop in the green part. The solution absorbs the light at those wavelengths but not at the wavelength range of green. The green is thus reflected off the solution and the solution will change into a green color. This is also seen in the spectras of spinach, chlorophyll a, and chlorophyll b, which are all colored green.
If we were given the spectras without any titles or information, we could match the solution’s identity by looking at the number or peaks and the wavelength range of each colored solution. By looking at the number of peaks on the graph and the ranges of where the peaks are, we can identify which solution it is. For example, for the 1:1mix solution, if there are two peaks, one at the wavelength range for blue and the other at the wavelength range for yellow, we will know that the solution definitely cannot be of blue or yellow color since the graph tells us that those lights are absorbed and will not be reflected. The graph also shows no peak at the wavelength range for green and will thus allow us to identify the green 1:1 mix. The way to distinguish Chlorophyll A & B is to look at the end peaks. Chlorophyll A has a higher end peak than Chlorophyll B. As for the blue food coloring, we can identify it by looking at the graph where there the graph is flat at the wavelength range of blue light (400~500nm). Similarly, yellow food coloring’s graph would have a flat surface at the wavelength range of yellow (500~600nm). We look for the maximum wavelength of each unknown solution and compare them to the color wheel to find the absorbance color. Then we match it to its complementary color and that determines the solution’s color. Solvent matters because it has small effects on the HOMO and LUMO gap affecting the color absorbed.
Solvent also matters because it is used as a blank for the measured solutions. If we do not use the correct solvent for each solution, the spectras would be inaccurate. The spectrometer is calibrated with the correct blank (solvent) in order to exclude the unnecessary spectra of the solvent to have a clearer spectra of the analyte we are observing.
F Value for Fluorescence spectrum of the diluted spinach extract solution: 0.08318
K= slope= .05615 (Rel/ppm)
Chlorophyll in Undiluted Spinach Extract Solution
(0.333)=(.05615 Rel/ppm) (c)
The concentration from #5 might be different from #6 because when we measure for absorbance, multiple wavelengths are taken into account. However, when measuring fluorescence, the concentration is measure at one wavelength and thus there is less variation.