Chromatography - Postlab Questions

Postlab Questions



2. The dyes present in the coloring used on pistachio nuts were analyzed. Click on the picture below to see the results. Suggest a method by which the dye sample spotted on the TLC may have been collected and then state what dye(s) were present in the sample.



3. Even though the samples were the same color, the orange cake dye and orange Koolaid contained different dyes. Suggest several factors that may have influenced the manufacturers decision to use one set of dyes over the other.

4. When the TLC of the dyes were developed in the ethanol-water solvent system the Rf values were much higher than when they were developed in the butanol-methyl ethyl ketone-water-ammonia solvent system. Explain why this might be true.

5. In the prelab you predicted which of the dyes would have the highest/lowest Rf values if the TLC were performed with a polar stationary phase and a relatively nonpolar mobile phase. The silica gel TLC plates and butanol-methyl ethyl ketone-water-ammonia solvent system used in this experiment fit this case. Compare your predictions to the results you saw.



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