Essay on Chromatography and Red Food Dye

Submitted By drummingspaz
Words: 1266
Pages: 6

Introduction:
Chromatography is a process which seperates a mixture into its seperate components by using the principle that different components will be attracted to a solid substrate differently. Coupling this knowlege with the use of a mobile phase (either gas or liquid) which travels across the substrate enables each component to be isolated due to the speed at which it spreads. The speed of each components spread is directly related to the strength of its attraction to the solid substrate; a stronger attraction means a slower spread and vice versa. Also, another side effect is that the more time which is given to the mixture to spread will be reflected in the isolation of each component as a result of their differences in speed. As a result, using liquid mobile phases typically takes longer than gas mobile phases due to their overall speeds of diffusion and effusion, respectively.
The use of chromatography is often for seperating homogenous mixtures and identifying the seperate components. However there are mixtures which must be seperated by different or alternative means due to the difficulty in distinguishing components. However, for our purposes of identifying which 'pure' colors reside in a food coloring and identifying the mixture of different chlorides in a mixture, chromatography works perfectly.
For paper chromatography, the calculatable constant which enables us to distinguish different components is found by use of this formula:
(1)
(1)
*The Rf value is always less than 1 because a component cannot spread faster than the carrier solvent.
In gas chromatography we rely on the device to detect the slight disparaties in color which are created by the introduction of each compound. This method is quite similar to paper chromatography in that the natural gas is the solvent for the mixture. Also, the packing which is used as the solid substrate in the same way as the paper does, slowing down each component in the vapor mixture at different rates.
However, the important measureable difference is in the time it takes for each component to reach the burner and the copper coil. So each component is identified by its delay rather than by a set distance like the Rf value.
Once we have determined the time it takes for each pure compund to pass through the packing, determining the unknown is simply done by way of comparing peak points with those of the pure compounds. Paper Chromatography
Data:
Dye Color

Color of Spot

Position of Spot(mm)

Red Food Dye

Red

59

Blue Food Dye

Blue

103

Yellow Food Dye

Yellow

83

Green Food Dye

Yellow

82

Blue

104

Red

60

Drink Mix "Cherry"

Calculations:
*Rf is in mm

122

(2)

59

(3)

103

(4)
(4)

83

(5)

59
122

(6)

103
122

(7)

83
(8)
122
Based on the position and color of the spot which originated from the Drink Mix, it can be concluded that the only dye present was the red food dye. Red food dye traveled 59mm whereas the
Drink Mix dye travelled 60, similar enough to be concluded. Also, they both possess the same color.
Green Food Dye is not a single color. It is a mixture of Blue and Yellow as can be clearly seen in the position and color of its two spots. Based on the same logic as concluding the Red Food Dye is present in the Drink Mix, only Blue and Yellow are present in the Green Food Dye, and the Green Food
Dye is a mixture.
Gas Chromatography:
Data:

Retention Time:
[Peak = 2.405] , [Occurance = 16.5]

Retention Time:
[Peak(1) = 1.551] , [Occurance = 17] | [Peak(2) = 1.834] , [Occurance = 31.5]

Retention Time:
[Peak(1) = 0.374] , [Occurance = 18] | [Peak(2) = 0.652] , [Occurance = {32,32.5}]
[Peak(3) = 1.902] , [Occurance = 49.5]

Retention Time:
[Peak(1) = 2.083] , [Occurance = 18] | [Peak(2) = 1.741] , [Occurance = 33]
[Peak(3) = 1.961] , [Occurance = {50,50.5}]

Retention Time:
[Peak(1) = 2.21] , [Occurance = 17.5] | [Peak(2) =…