Question

(5) You dropped and mixed up your samples. You know that one contains only valine, one contains valine and glycylvaline, one contains valine and alanine, one contains only glycine and valine, and one contains glycine and glycylleucine. How would you determine what your samples are using TLC and the data below? Can you figure out what they all are? R Values for Amino Acids and Dipeptides Color Compound 0.26-0.29 0.39-0.42 0.62-0.66 0.62-0.64 0.76-0.80 purple purple gray purple light brown glycine alanine glycylvaline valine glycylleucine Rt values taken two days after solvents were mixed and with solvent advance 100 mm in 43 minutes at a temperature of 31°C

Answer 1

TLC spots can be used to distinguish between samples on the basis of TLC.

The five samples will be as below:

a) Only 'valine' sample will have TLC spot with Rf between 0.62 - 0.64 (~0.63) will appear purple on plate.

b) Valine and glycylvaline mixture will have two TLC spots at

Rf = 0.62 - 0.64 (~0.63) due to valine (purple)

Rf = 0.62 - 0.66 (~0.64) due to glycylvaline (gray)

c) Valine and Alanine mixture will have two spots on TLC,

Rf = 0.62 - 0.64 (~0.63) due to valine (purple)

Rf = 0.39 - 0.42 (~0.41) due to alanine (purple)

d) Glycine and Valine mixture will have two spots on TLC

Rf = 0.26 - 0.29 (~0.27) due to glycine (purple)

Rf = 0.62 - 0.64 (~0.63) due to valine (purple)

e) Glycine and glycyleucine mixture will have two spots on TLC

Rf = 0.26 - 0.29 (~0.27) due to glycine (purple)

Rf = 0.76 - 0.80 (~0.78) due to glycyleucine (light brown)