Pentobarbital is a weakly acidic drug that is used with animals and can be present in small amounts in raw milk. To quantify this drug in raw milk, the first step is to perform a liquid-liquid extraction of the pentobarbital from the complex aqueous mixture that is raw milk. The initial extraction was performed by adding acetic acid and acetonitrile to the milk. The pentobarbital will end up in the less polar acetonitrile layer. Why does adding acetic acid to the milk improve the extraction efficiency of the pentobarbital?You have 50 mL of raw milk already acidified with the acetic acid. The partition coefficient of pentobarbital is 5.82. Calculate the extraction efficiency if you use 10 mL of the acetonitrile to extract the pentobarbital.If you wanted to be sure you removed at least 95% of the pentobarbital from the milk, how many sequential 10-mL extractions would you need to perform?

In liquid–liquid (solvent) extraction, the solute partitions itself between two immiscible phases.…

Answered: Why does adding acetic acid to the milk…

9th Edition

ISBN:9781319114671

Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.

Chapter1: Biochemistry: An Evolving Science

Section: Chapter Questions

Problem 1P

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Pentobarbital is a weakly acidic drug that is used with animals and can be present in small amounts in raw milk. To quantify this drug in raw milk, the first step is to perform a liquid-liquid extraction of the pentobarbital from the complex aqueous mixture that is raw milk. The initial extraction was performed by adding acetic acid and acetonitrile to the milk. The pentobarbital will end up in the less polar acetonitrile layer.
1. Why does adding acetic acid to the milk improve the extraction efficiency of the pentobarbital?
2. You have 50 mL of raw milk already acidified with the acetic acid. The partition coefficient of pentobarbital is 5.82. Calculate the extraction efficiency if you use 10 mL of the acetonitrile to extract the pentobarbital.
3. If you wanted to be sure you removed at least 95% of the pentobarbital from the milk, how many sequential 10-mL extractions would you need to perform?

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