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Tran Nguyen CHEM 225 Prof. Khong Partner: Julio Gonzalez Experiment #1: Column Chromatography and UV/Visible Spectroscopy Calculations

Conclusion - It is obvious that Column chromatography did a really great job at separating the carotenes from other pigments, because the TLC plate has shown that there are no other pigments (besides carotenes) visible on the yellow band. - Compared to groups with other vegetables, some of them also have an efficient separation of carotenes, while some still have another blurry spot on their yellow band, according to their TLC plates. However, the yellow colors of their TLC plates are all positioned at the same spot (on the very top). - The column chromatography may have produced slightly different results because of the techniques used, contamination, or small mistakes students made during the experiment. However, all the vegetables produce pigments with similar absorbance values according to the observations made during lab, despite that the wavelengths are a little different.

Post-lab Questions 1. For a better separation, the spot should be concentrated in a small area, so adding as little solvent as possible would result a small width of colored (green/yellow) bands. 2. As we are using petroleum ether, which is mostly non-polar structured, to run the column chromatography, the yellow band (carotene), which is also mostly non-polar structured, would elute earlier before the green band (chlorophylls), which are mostly polar. 3.

References Klein, David R. Organic Chemistry. 3rd Ed. Johns Hopkins University, 2017. Mohrig, Jerry J. Laboratory Techniques in Organic Chemistry, 4th Ed. Freeman, 2014. Speakman, Teresa J. Chemistry 225 Laboratory Manual, Golden West College, 2018....