Question

An unknown mixture was analyzed using TLC on a silica gel plate and developed in 1:6 ethyl acetate:hexane, and gave 2 spots with Rf values of 0.6 and 0.5 respectively. 1)Would this be considered a good separation between the two? Briefly explain. 2)Which spot represents the more polar compound(s)? 3)Can you say for sure how many compounds are contained in the mixture? If so, how many are there? Briefly explain. 4)If not, what further conditions might be performed to determine the number of components in the mixture or to obtain a better separation? Explain. 5)Suppose you carry out a TLC separation of acetaminophen and aspirin on silica gel using a nonpolar eluting solvent, hexane. Which should have the larger Rf value? Briefly explain. 6)What are the methods for "visualizing" spots on TLC plates that we will use in this lab?

Answer 1

An unknown mixture was analyzed using TLC on a silica gel plate and developed in 1:6 ethyl acetate:hexane, and gave 2 spots with Rf values of 0.6 and 0.5 respectively.

1)Would this be considered a good separation between the two? Briefly explain.

Solution :- The Rf values are are 0.5 and 0.6 which are very close means the separation is not good so we can say it is not good separation for the two componds.

2)Which spot represents the more polar compound(s)?

Solution :- The spot with Rf value 0.6 will be more poalr compound because it can move farthest with polar solvent system.

3)Can you say for sure how many compounds are contained in the mixture? If so, how many are there? Briefly explain.

Solution : - the TLC gives two spots and two Rf values so it have 2 compounds for sure.

4)If not, what further conditions might be performed to determine the number of components in the mixture or to obtain a better separation? Explain.

Solution :- If there are more than 2 compounds then we can change the solvent system composition and check the TLC again.

5)Suppose you carry out a TLC separation of acetaminophen and aspirin on silica gel using a nonpolar eluting solvent, hexane. Which should have the larger Rf value? Briefly explain.

Solution :- acetaminophen is more polar then aspirin therefore when only non polar solvent system is used then acetaminophen will move less than aspirin. So the Rf value of the aspirin will be higher than acetaminophen.

6)What are the methods for "visualizing" spots on TLC plates that we will use in this lab?

Solution :- To observe the TLC spots on TLC plate UV light or iodine chamber is used.