Introduction:

Our purpose for this lab was to separate dye colors from each other using TLC (Thin Layer Chromatography), and Column Chromatography.

Results:

TLC:

Table 1.1: Seperation using K2SO4:H2O:CH3CNDye color on TLC plate

Distance of dye from the pencil line (cm)

Purple 5.8

Yellow 5.4

Yellow (mixture) 5.1

Blue 3.8

Blue (mixture) 3.9

Table 1.2: Seperation using 95% ethanolDye color on TLC plate

Distance of dye from the pencil line (cm)

Purple 5.7

Yellow 0

Yellow (mixture) 0

Blue 3.5

Blue (mixture) 3.4

The above tables depict the two different trials that were conducted using two

different solvents which were 95% ethanol and potassium sulfate mixture. The mixture

solution for each trial was separated into three colors; yellow, blue and purple.

Column Chromatography:

The solvent 95% ethanol was added to the column that contained the alumina

substance and the sand. After the pressure was released, there was a pure blue solution

gathered by the beaker below the column. While using another beaker to collect the next

round of solution, a 0.1 M of NaOH was then added to the same column and the pressure

released by the stopcock to give a solution that was green in color.

Discussion:

TLC:

In this experiment, the colors yellow and blue that are captioned (mixture) are the

colors that have separated from the mixture of both methyl blue and fluorescein dye. The

solvents for the two different trials were potassium sulfate and 95% ethanol. The reason

why two solvents were used each for a different trial was is because some of the dyes

may or may not dissolve in one of the solvents. The distance traveled upwards by a

certain color signifies its solubility in that compound. For both solvents, methylene blue

is less soluble than fluourescein yellow because it traveled a smaller distance up the TLC

plate, whereas none of the two yellow dyes in Ethanol 95% traveled up the TLC plate.

This is due to the insolubility of fluorescein in Ethanol. Any color that showed up in the

TLC plate that was not yellow or blue would definitely have been an impurity or a

mixture of foreign compounds. This method of color dye separation is in this case more

informative when potassium sulfate is used as the solvent since all three mixtures are

moving up the TLC plate. The TLC method also implies that the impurity (in this case

the purple dye) within the blue and yellow mixtures is even more soluble in both

potassium sulfate and in 95% ethanol because of the observed distance the purple dye has

traveled up the TLC. The yellow fluourescein and methyl blue appear to be just as

soluble in both pure form or within the mixture solute.

Column Chromatography:

We know from our experiment with TLC that 95% ethanol was not as good a

solvent for the color mixture as was the potassium sulfate. When we introduced the 95%

ethanol to our column, we collected blue solution. This indicates that even in column

chromatography, ethanol had only dissolved the methylene blue and brought it down to

the beaker. On the other hand, when adding NaOH to the column, both dye colors were

dissolved and gathered down to the beaker which clearly indicates that both blue and

yellow dyes were gathered since green is a mixture of both blue and yellow.

Conclusion:

We can conclude from this experiment that if we want to isolate methylene blue

only, we should use ethanol to gather it as a pure substance. If we were to isolate both

fluourescein yellow and methylene blue from the rest of the impurities within the

mixture, our ideal solvent would be either NaOH or Potassium Sulfate depending on what

method we are using. It is very important what solvent we use to isolate certain

compounds depending on what and how many of these mixtures do we want to separate.

Appendix:

Rf= b/a= Distance traveled by spot / Distance traveled by solventPotassium Sulfate:Fluourescein yellow = 5.4cm / 6.2cm = 0.871Methylene blue = 3.8cm / 6.2cm = 0.613

95% ethanol:Fluourescein yellow = 0cm / 6.1cm = 0Methylene blue = 3.5cm / 6.1cm = 0.574

Questions:

1. The silicon dioxide molecule has a strong dipole moment, and since the

methylene blue and fluourescein yellow are also polar, the dipole-dipole

interactions between SiO2 and fluourescein yellow and methylene blue. The rule

“like dissolves like” would also confirm this phenomenon.

2. The student did not allow the complete drainage of the 1st solution with the 1st

solvent. This is why when he/she drained the solution the next day, the remaining

1st solution that was not drained had mixed with the 2nd solution that was supposed

to be drained separately.

3. Reverse phase chromatography is a relatively newer method in separate mixtures

instead of the traditional column and TLC methods. This new method deals with

covalently bond alkyl compounds after isolating the polar residues.