An assay of morphine in opium is proposed which utilizes both adsorption and colorimetric procedures.
INCE the discovery of morphin n 1803 by analysis of opium has appeared. The assay of o p h given in t h e majority of pharmacopeias is by either the Helfenberger or the lime method (12), and most of the literature deals with modifications of these methods. Methods utilizing polarography (11), colorimetry (1,4,5, 13, 14, 16, I i ) , andion-exchange (10) have also been reported. Adsorption procedures on opium (3, 6) have been carried out, using alumina as the adsorbent. The official opium assay, which is extremely long and tiring, is believed t o give b w results, which Rosin and Williams (12) found t o be due to various factors such as the loss of the alkaloid in t h e solvent and incomplete liberation from lime. Ammonium chloride, used t o precipitate the morphine in the last step of the U. S. P. method, will also dissolve some of t h e alkaloid. They also noticed t h a t results differed when there was a variation in the temperature at which the formation of morphine crystals takes place. Another disadvantage of the official assay, observed in this laboratory, is the adsorption of interfering colored extractive material on t h e precipitated morphine crystals, which makes the end point in titration rather difficult to see. I n this investigation, a short, simple, and direct one-solvent extraction (using a minimum amount of solvent), an adsorption column t o remove interfering material, a n d a final colorimetric determination of morphine were employed.
s Sertiirner (9), a great deal of liter 7 ture on the
EXPERIMENTAL
The elution apparatus of Stolman and Stewart (15), described in their work with morphine, codeine, and heroin in viscera and body fluids by adsorption, was employed. It was found that extraction and elution could be accomplished at one time by lengthening this apparatus and placing a glass thimble above the adsorption column (Fig. 1).
A number of reagents were tested for the colorimetric morphine determination. The Folin-Ciocal-*