Procedure: 1) Grind grass in mortar pestle
2) Soak grass grindings in chromatography solution
3) Cut chromatography strip into about 12.5 cm
4) Draw a straight, horizontal line about 2 cm from the bottom of the strip using a pencil
5) Paint thin line of grass solution over the pencil line and let it dry under the heat lamp; repeat 5 times
6) Place chromatography paper strip in chromatography jar with about 1 cm of solution in the bottom of the jar. Make certain the line is not in the solution.
7) Allow the pigments to separate for about 15-20 minutes
8) Take paper out of jar and allow to dry
9) Cut out the individual colors
10) Dissolve the individual colors in chromatography solution ?10 mL’s
11) Pour the dissolved solution into marked chromatography test tubes
12) Pour plain chromatography solution into one chromatography test tube. This will be the blank.
13) Place blank in photospectrometer, set wavelength, and zero out. Make certain there are no fingerprints on the test tube and line up the arrow.
14) Remove blank and place the pigment in. Record the absorbance.
15) Repeat 13 and 14 for all wavelengths and pigments.
Data Collection and Processing:
Data Collection Table:
Data Processing: No calculations were needed.
Data Presenting/graph:
Conclusion and Evaluation:
Conclusion:
When this experiment was conducted, there was a limited amount of time to collect the data and one group never finished theirs. The pigment they were testing was xanthophyll. I chose not to include that data in my write up as it was incomplete and therefore invalid. (Aside from that the data that was produced with xanthophyll had a high outlier and seemed incorrect.) As for the other three pigments, they all had a limited range in absorption spectrum. Chlorophyll a ranged from 0 to 0.06, chlorophyll b ranged from 0 to 0.02, and caratene from 0 to 0.03. The data overall appears to be unreliable for any real conclusions to be made. This is because the numbers didn't show any definite trend either with increasing or decreasing, and most of the data gained was all zeros.
Evaluation of procedure:
The procedure did not work as planned for the most part. The time constraint made it difficult to be exact in the first place, (i.e. xanthophyll). Plus each group was working with a different photo- spectrometer machine. This means that there were four different machines with four different calibrations that are each producing slightly different data. One group's value of 0.01 might have come out to 0.02 on another machine. There were not enough samples as well. Grinding our own grass only added to the variables. On top of all that, the majority of the class was confused about the procedure and that could be the reason why the data does not show anything conclusive.
Improving Procedure:
More trials would have increased the accuracy of the experiment. Although it would take a longer period of time, using one machine to collect data from would also help. I were were wanting to further the procedure for a future experiment, I might test other plant species instead of just grass. This would give me a broader spectrum to draw conclusions from. It might also be interesting to comparatively test traditional indoor plants to outdoor plants.
