Question

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.

Short answer

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

Step-by-step solution

Definition of Barbital.

• 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.

Determine the procedure.

• 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