Science Buddies: "Ask an Expert"

Science Buddies has truly wonderful projects. I'm glad I can try this out for myself. I think it will impress my 8th grade science teacher.
Anyway , I need to ask a question. I know that the retention factor is:

The relationship of the distance moved by a pigment to the distance moved by the solvent front is specific for a given set of conditions.

I understand this to an extent, but could you go deeper into this explaining it in simple language? I'd like to explain it to my peers when I present it to the class so they can understand it too.
Thanks in advance,
Nikki (8th grade student)

Was also going to use the name: Reveal the Red.

Any other suggestions for punny, funny, and catchy names for my science fair project?

Hi yayapizza,

In chromatography the retention factor is the distance a solute (something dissolved in the solvent) moves on the paper divided by the distance the solvent moves. A solute cannot move past the solvent front, so the retention factor can have values between 0 an 1.

A low retention factor (closer to 0) suggests that the solute has little interaction with the filter paper. Higher retention factors indicate more interaction with the paper.

Chromatography experts can “juggle” the characteristics of the stationary phase and solvent to separate very chemical complex mixtures. Once the chromatography conditions are set, retention factors can be used to distinguish components of a mixture.

The following links have additional information on paper chromatography and retention factors.

http://www.chemguide.co.uk/analysis/chr ... paper.html

http://genchem.rutgers.edu/chrompap.html

https://en.wikipedia.org/wiki/Paper_chromatography

I hope this helps. Please post again if you have more questions.

A. Norman

Thank you. I understand now.

Hi,

I am using this experiment and was wondering exactly what the pH of the 70% isopropyl alcohol diluted with water was.

Thanks

Hello twil43,

Alcohols don’t normally dissociate into ions when mixed with water. Thus the pH of 70% isopropyl alcohol in water should be neutral (very close to 7).

I hope this helps. Please post again if you have more questions.

A. Norman