Chromatography Lab

Similarities of Red 40, blue 1, and yellow 5

-Sulfite Sodium molecule -aromatic rings (6 Carbon pronged molecules) -have non polar bonds and polar bonds but overall are polar molecules

Differences of Red 40, blue 1, and yellow 5

-blue dye forms ion-dipole bonds because of containing a cation and an anion -blue does not have a double nitrogen bond, HO, or NaO3S -blue has 5 aromatic rings while red and yellow have 3

What are the main parts of this experiment?

1. comparing separation of 3 FD&C dyes using 2 solvents 2. design an experiment to identify the solvent with the man resolution of a mixture of dyes 3. Study connection between structure and mobility of dyes

Of the original 695 color additives how many are still used today?

2

How many color additives total are used today?

7

Difference between absorption and adsorption

Absorption: fluid is dissolved by a liquid or solid Adsorption: atoms, ions, or molecules from a substance adhere to a surface of the absorbent

What are the two main components of chromatography?

Adsorbent and the eluent

What are the purposes of the two main components of chromatography?

Adsorbent: solids that will attract and adsorb the material to be separated Eluent: the solvent that carries the materials to be separated through the adsorbent

For the intro activity, which dye was more compatible with the mobile phase and which one was the least?

Blue was the most because it had the highest Rf value while red was the least because it had the lowest Rf value

What is the scientific term for the container where you pour the eluent in and carry out the separation?

Erlenmeyer Flask

Which mobile phase was better for dye separation? Do the results support the predictions?

NaCl was better than IPA, experimental results supported predictions, NaCl forms ion-dipole bonds with water and IPA forms hydrogen bonds, ion-dipole bonds are stronger alluding to a stronger attraction to the adsorbent and a more successful mobile phase

Based on Rf values of sample A and B, what can you conclude about the IMFs both samples have for the eluent and paper?

Sample A (higher Rf): stronger attraction between the paper and the eluent Sample B (lower Rf): less attraction between the paper and the eluent, also less polar eluent

What is the rate of flow? How else is it called?

The distance a sample moves along a chromatography paper compared to the overall distance the solvent moves (aka Rf value)

For the guided inquiry activity, did your choice of mobile phase work out as expected?

Yes, NaCl separated more (higher Rf values) than IPA

Explain IMFs between paper and red 40, blue 1, and yellow 5.

blue 1: ion-dipole red 40 and yellow 5: hydrogen bonding all dyes have London dispersion

Why does changing the polarity of the eluent affect the separation of a mixture so much?

changing the polarity can greatly change the relative attraction for the adsorbent

What is the most difficult task in chromatography?

choosing a good eluent

What is the adsorbent in paper chromatography?

chromatography paper

What could have been done to determine whether a color additive was harmful before it was used in the food industry?

could have tested them with experiments

How is rate of flow calculated?

distance sample moves/overall distance solvent travels

Experiment's safety hazards

isopropyl alcohol is a moderate fire risk and slightly toxic by ingestion or inhalation FD&C dyes are slightly hazardous by ingestion, inhalation, and eye contact All dyes are irritating to skin and eyes

What is capillary action?

liquid flowing into a narrow tube opposite of gravity

When there are 2 spots on the paper chromatogram, what does this tell you about the composition of the sample?

made up of 2 different molecules with 2 different polarities

What were food color additives initially used for?

make food more visually appealing to the consumer and to mask poor quality foods

What is another name for the solvent or eluent?

mobile phase

Which types of molecules will move up the fastest with the eluent in paper chromatography?

molecules that have a polarity closest to the polarity of the eluent

How can you judge whether a mixture was separated properly by chromatography?

organic molecules are spotted on the paper strip separate because they are carried at different rates

Stationary phase

paper

Predict the IMFs between paper and water. How do these interactions explain paper's hydrophilic nature?

paper and water form hydrogen bonds which have a very strong attraction, paper's hydrophilic nature strongly attracts water

What factors determine whether the separation by the eluent will be successful?

polarities and the affinities of the components of a mixture for the eluent (varying affinities=separation)

Predict and rank the strength of IMFs experienced by red 40, blue 1, and yellow 5

red<yellow<blue, based on Rf values (higher Rf value, stronger attraction)

Mobile Phase

solvent

If your mobile phase did not work as expected, what mobile phase would you choose instead?

something more polar like HCl because if the molecule is more polar, it has a stronger attraction with the adsorbent and a more successful mobile phase

What is another name for the adsorbent?

stationary phase

What concept does chromatography work on?

that the compounds to be separated are slightly soluble in the eluent and will spend some time in the eluent and adsorbent

Solvent Front

the height the solvent goes up to on the chromatography paper

What do all FD&C-approved food dyes chemically share in common?

they are charged, water-soluble, organic compounds that bind to natural ionic and polar sites in large food molecules

Why were almost all of the original food color additives phased out?

they were discovered to be harmful or toxic

What is this experiment's objective?

to investigate the factors that influence the separation of food dyes using paper chromatography

What is chromatography used for?

used to separate organic compounds for identification or purification