Consider the following molecules and their properties for 1poim questions 7-9 Po

Question

Consider the following molecules and their properties for 1poim questions 7-9 Polybrominated diphenyl ethersowBoiing Point (°C) 300 penta-brominated diphenyl ether 320 Br deca-brominated diphenyl ether 6.29 330 octa-brominated diphenyl ether 7. Kow is a partitioning coefficient of molecules between octanol and water. A larger number means the molecule preferentially partitions into the octanol. Write the mathematical expression for Kow for the penta-brominated diphenyl ether. Your answer 8. Use the Kow to predict the elution order from HPLC2 points reverse phase and normal phase. Your answer 9. What order would they elute for GC and how would you determine this? 2 points

Explanation / Answer

7. Kow= [pentabrominated dipheyl ether] in octanol / [pentabrominated diphenyl ether] in water = 6.57 * [pentabrominated diphenyl ether]in water/ [pentabrominated diphenyl ether] in water

8. More polar compounds have more retention time in normal phase HPLC. And Kow of a molecule leads to less polarity. So elution order is:decabrominated diphenyl ether (elutes first), octabrominated diphenyl ether (elutes second), pentabrominated diphenyl ether (elutes last)

In reverse phase the order is: pentabrominated diphenyl ether (elutes first), octabrominated diphenyl ether (elutes second), decabrominated diphenyl ether (elutes last)

9. In GC more volatile (less boiling point) compound elutes fast.

The order of elution is : pentabrominated diphenyl ether (first), decabrominated diphenyl ether (2nd), octabrominated diphenyl ether (3rd)

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