Map @mixture of six nonpolar compounds was introduced to an HPLC with a Cre stat

Question

Map @mixture of six nonpolar compounds was introduced to an HPLC with a Cre stationary phase for separation. How would the retention time and peak resolution for the mixture be affected if the solvent ratio was changed from 45% water. 55% acetonitrile to 20% water: 80% acetonitrile? longer retention time, er peak resolution shorter retention time, lower peak resolution shorter retention time, higher peak resolution o longer retention time lower peak resolution The two components below are part of the mixture described above. Which will elute through this column first if the pH of the solution is 4.0? CH, CH,),COOH CH, CIH,) NH, O CH3(CH2)sNH2

Explanation / Answer

stationary phase is nonpolar, therefore

changing from slightly polar, to mostly nonpolar solvent will:

shorter retention time --> since species have much more affinity towards the stationary phase

expect a lower peak resolution, because of the same reason

they will

As the polarity of solvent deceases the non-polar compounds will come out immediately making shorter retension time and also lower peak resolution.

b)

the NH2 grou pwill be protonated at such pH:

CH3(CH2)5NH2 will elute first.

At this pH = 4 --> NH2 forms NH3

it becomes more polar than the acid.

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