Colorimetric determination of acetylenic hypnotics by formation of silver acetylides

A colorimetric method is described for the determination of certain mono-substituted acetylenic hypnotic drugs--ethinamate, methyl pentnol carbamate, and ethchlorvynol. Silver acetylide is formed and extracted into isobutyl methyl ketone. After acidification, an equivalent amount of silver ions is liberated which is assayed colorimetrically as silver dithizonate (lambda mx. 472 nm). About 10--50 microgram compound could be assayed with good accuracy. The procedure is reproducible and precise (standard deviation 1.5--2.19%). The procedure was successfully applied to different pharmaceutical dosage forms.