PLs Help . Thank YOu!!! 2. Find the Rf value of each of the five spots mentioned

ID: 875548 • Letter: P

Question

PLs Help . Thank YOu!!!

2. Find the Rf value of each of the five spots mentioned above. Which compound above would likely have the highest Rf value if the above plate was run with a polar solvent and non-polar plate (reverse-phase chromatography)?

3. How do you know how much material to spot in each lane of the TLC plate? What would happen if you spotted too much or too little sample?

4. What would occur if your developing solvent was above the line where your samples were spotted?

5. What would happen if you forgot to put a solvent wick in your developing chamber when performing a TLC run?

6. Visualizing spots once the plate is run is crucial in determining the components in the mixture. The above TLC was stained with vanillin in sulfuric acid to visualize the compounds in each essential oil. In our lab, UV will visualize compounds with conjugated double bonds and iodine will stain double bond-containing compounds and some oxygen containing functional groups. Which visualization method would you perform on each of the five molecules above?

7. What are some possible reasons that we did not employ TLC analysis on the Group Project? What advantages does gas chromatography have over TLC?

Explanation / Answer

TLC separation is centered on the polarity of the compound and its interaction with the stationary phase under the influence of the mobile phase.

Eugenol > Linalol > Cedrol > Linalyl acetate > Caryophyllene.

Thus, the spots identified as,

G2 = Eugenol

C1 = Linalol

B1 = Cedrol

G1 = Linalyl acetate

L2 = Caryophyllene

Rf value = distance travelled by the solute / distance travelled by the solvent.

So, the calculated values for samples are:

G2 = 8.0/9.0 = 0.89

C1 = 7.5/9.0 = 0.83

B1 = 5.75/9.0 = 0.64

G1 = 5.8/9.0 = 0.64

L2 = 4.5/9.0 = 0.50

The compound with the highest Rf value in reverse phase chromatography would be, Eugenol because polar will be eluted with polar solvent.

(3) For Thin layer chromatography, a very dilute sample of solute in a solvent is used for the purpose of spotting. The spotting should just be sufficient to observe with naked eye, but not too high in concentration. High concentration of solute while spotting will cause the solute to spread and not give good separation on TLC plate, thus giving the wrong Rf value, very little sample would not be enough to reach the proper Rf value and would not separate as it is supposed to.

(4) If the solvent level of developing solvent was kept above the spots in the developing chamber, The TLC would not run. To develop and have separation of the mixture or compound, the spots must touch the developing solvent or somewhat below it, but it should not completely be submerged in it.

(5) Solvent wick helps to saturate and make uniform atmosphere in the development chamber with solvent vapor. Absence or uneven saturation of it would because the spots to bend as a result not giving a good chromatogram.

(6) All the compounds given above can be identified using UV light as the detection tool.

(7) Gas chromatography is more sensitive than TLC. It is employed for compounds that can be converted into vapor form. Gas chromatography uses very small amount of sample and is more accurate and quantitative in nature when it is run with standards.TLC separation is centered on the polarity of the compound and its interaction with the stationary phase under the influence of the mobile phase.