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Column Chromatography Technique Quiz

1) You want to separate compound A from compound B by flash chromatography. The following are the results of running these two compounds in different hexanes/ethyl acetate systems. Which is the best solvent system to elute compound A? Compound B?

TLC plates

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2) A student loaded a mixture onto a small flash chromatography column in 1 mL of methylene chloride, then proceeded to elute with hexanes/ethyl acetate 10:1. He/she found that all of the mixture came off in the first 4 fractions, with no separation. What technical mistake did the student make?

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3) You only see one compound coming off the column when you suspect two. Where might the other compound be? How can you recover this compound?

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