Chapter 28: Q14P (page 790)

Barbital can be isolated from urine by solid-phase extraction with\({{\bf{C}}_{18}} - \)silica. The barbital is then eluted with\({\bf{1}}:{\bf{1}}\) vol/volacetone: chloroform. Explain how this procedure works.

Expert verified

Barbital has the higher affinity for water so it is retained by the column and barbital dissolve in acetone.

Step by step solution

Barbital (or barbitone) was the first commercially accessible barbiturate, marketed under the brand names Veronal for the pure acid and Medinal for the sodium version.
From 1903 to the mid-1950s, it was used as a hypnotic (sleeping aid).
Barbital's chemical names are diethylmalonyl urea or diethylbarbituric acid; as a result, the sodium salt (marketed as medinal in the United Kingdom) is also known as sodium diethylbarbiturate.

Barbital is isolated from urine by solid- phase extraction with \({{\rm{C}}_{18}}\)-silica.
It is then eluted with \(1:1\) vol/vol acetone: chloroform. Here we will explain how would this procedure work.
Barbital has a higher affinity for the \({{\rm{C}}_{18}}\)-silica phase than for water so it is retained by the column - this happens due to nonpolar properties of barbital considering also that it is highly hydrophobic
The barbital would dissolve in acetone: chloroform which would elute it from the column

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