Barbiturate Differentiation by Chemical Microscopy

Abstract

Of the crystal tests currently in use for the identification of narcotics, it would appear from the literature that many of them were developed as a result of research in toxicology, where they have been largely supplanted by spectrophotometric and other advanced methods. Such tests as have been developed, however, retain their reliability and utility for the qualitative analysis of confiscated and are included in standard texts within this field. Additional information is accessible to the worker, in bulletins and manuals dealing specifically with the narcotic problem, and the criminalist who is generally familiar with the subject of chemical microscopy has no difficulty in finding suitable tests for these materials. With respect to the dangerous drugs, however, a somewhat different situation exists. Many of the drugs currently on the market (and encountered in the drug traffic) are not narcotics, but are nevertheless controlled by various drug laws. Possession of hypnotic and stimulant drugs without a prescription may be a violation, and the criminalist is often called upon to identify an unknown pill, capsule, or powdered material of this type. Of these, the barbiturates are perhaps the most common. An examination of the usual texts in criminalistics, however, reveals little in the way of new information or tests for such materials. For the most part they include little more than the standard color reactions, melting point data, and related information adapted from earlier works. While considerable work has been done on the barbiturates with paper chromatography, and the spectrophotometer, these methods are not well suited to the rapid identification and differentiation of individual barbiturates. Although spectrophotometric, chromatographic, or melting point and color-test methods may identify the barbiturates, such procedures cannot compare with the simplicity of the usual crystal tests for the narcotics. It is true that crystal tests have been developed for a number of the barbiturates, but a limited review of the literature fails to indicate any general scheme or procedure applicable to the barbiturates as a group, and capable of differentiating between them. Believing the need for such a procedure to exist, this writer began in February, 1960, an investigation into certain crystal reactions which seemed best suited to the solution of the problem. As a result of work performed, a simple procedure has been worked out which has thus far proved most encouraging, and which has permitted the identification and differentiation of most of the barbiturates tested. Research on this project resulted in the formulation of a new silver reagent which is particularly well suited to barbiturate testing, and which represents the most useful reagent of the series. Basically, the recommended procedure consists of the following tests. First apply Koppanyi's test.' If positive, utilize remaining tests. (1) Dissolve a small amount of the material in 2% potassium hydroxide solution (KOH), then add syrupy phosphoric acid to precipitate the drug. (2) Dissolve a small amount of the material in concentrated sulfuric acid, then add water to precipitate. (3) Test with Wagenaar's Reagent (5 % aqueous copper sulfate plus sufficient ethylenediamine to give a purple liquid). (4) Test with author's reagent (10% aqueous silver nitrate to which is added 15% ethylenediamine by volume). Tests (1) through (4) are performed on a microscope slide, using drop-quantities of the reagents.2 1 Drug on filter paper, add drop of 1% cobaltous acetate in methanol and follow with 5% isopropylamine in methanol. Pinkish violet for positive reaction. 2 Tests included here were selected primarily on the basis of capacity to differentiate between the greatest