Experiment 3B: Separation of a Mixture by Paper Chromatography

Experiment 3B:

Separation of a Mixture by Paper Chromatography

What is chromatography anyway?

It's a technique to separate mixtures of all kinds of chemical compounds used by chemists.  It's used to isolate and/or identify a mixture's components.



And why is that important?!

Because it has many practical applications such as determining the amount of pesticides in foods or drugs in a sample of urine.


In experiment 3B, my chemistry class tested various food colouring samples to to determine their Rf value (Rf = ratio of fronts).

We determined this value by using the formula: Rf = d1 . 
                                                                                                                   d2
Where d1 represents the distance travelled by the solute
and d2 represents the distance travelled by the solvent.

Note: The Rf value of a subatance will always be between 1 and 0.

For example:


Within Lab 3B, we measured the distance from the origin ( our pencil mark ) to the solute front (where the food colouring rose to); for d1.
Then we measured the distance from the origin to the solvent front ( where the water rose to ); for d2.  Lastly, we divided these two measurements.

Afterwards, we compared our results to Table 4 which contains the dyes approved for food colouring to see whether or not we used any of the dyes listed. 


What did I learn from this epic lab???

1. That food colouring is magical! Just kidding... I learned that despite my class was given the same instructions the results varied. Therefore one can conclude that many samples need to be taken to obtain accurate results.
2. That paper chromatography will not only determine Rf values but will also separate the components tested.  (e.g. the food colouring mixtures separted into their primary colours).

Here's a video of paper chromatography!