What would be the result of failing to mark the solvent front after developing a

Question

What would be the result of failing to mark the solvent front after developing a TLC plate? Would this affect your ability to calculate component R_f values? Why or why not? What would happen if your origin line was oriented so low on the TLC plate that when it was lowered into the TLC chamber it was positioned below the level of the developing solvent (eluent)? Assuming that the separation of a binary mature in ideal circumstances (concentrated spotting) would be relatively small (less than 0.5 cm), what would be the result of applying too large a spot of this mixture to the TLC plate? How would it affect your ability to distinguish one component from the other on the plate? How would it affect your R_f values? Draw a sample TLC plate to help illustrate your answer. Unknown compound Q is spotted on a TLC plate that is then developed in cyclohexane. The solvent front is measured at 5.2 cm and the distance traveled by compound Q is measured at 3.4 cm. A sample of acetaminophen is spotted on a TLC plate that is then developed in cyclohexane. The solvent front is measured at 4.15 cm and the distance traveled by acetaminophen is measured at 2.70 cm. What can be determined about the identity of compound Q in light of this data? Describe how TLC could be used to monitor a reaction's progress (product & byproduct formation) in a research/teaching laboratory.

Explanation / Answer

1. The result of failing to mark the solvent front after developing a TLC will affect the calculation of Rf values.

Retention factor or Rf is equal to the distance migrated by the sample over the total distance covered by the solvent. In the beginning the solvent front will appear as a wet line, but on drying it will become invisible. Since, we didnt mark the solvent front, we will be unable to calculate the total distance covered by the solvent and it will affect the Rf calculation.

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