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Chromatography Lab

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Riley Lambertsen Period 4 IB Bio Absorption Spectrum of Grass Date: 1/13/08 Design: Research Question: What is the absorption spectrum of the pigments in grass? Hypothesis: Cannot be determined Relevant Variables: Temperature, type of solvent, color of solvent, type of plant, surface area, time, light source Independent Variable: Absorption of light wavelengths by pigments in grass Dependent Variable: Percent absorbance of wavelengths of light Control of Variables: Maintain constant room temperature, use the same organic solvent throughout entire experiment, zero machine to solvent blank, use same plant (grass), mortar-pestle grass Materials: mortar, pestle, photo spectrometer, grass, chromatography solvent, chromatography jar, chromatography paper/strip (12.5 cm), photospectrometer test tubes, paint brush, Kim wipes, heat lamp, pencil Procedure: 1) Grind grass in mortar pestle 2) Soak grass grindings in chromatography solution 3) ...read more.


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: Wavelength Chlorophyll a Chlorophyll b Carotene 400 0.05 0.01 0.02 420 0.06 0.02 0.01 440 0.04 0.02 0 460 0.01 0.01 0.02 480 0 0 0.03 500 0 0 0.02 520 0.01 0 0 540 0 0 0 560 0.01 0 0 580 0.01 0.01 0.01 600 0 0 0 620 0 0 0.01 640 0.01 0 0 660 0.03 0 0 680 0 0.01 0 700 0 0.01 0.01 720 0 0 0 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. ...read more.


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. ...read more.

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