Nitroglycerin solutions in sunflower oil and ethanol: Properties and production technology

Abstract

Nitroglycerin (biG) preparations are widely used in the therapy and prophylaxis of diseases such as spasms of the coronary vessels and many others [I -5]. Despite a large variety of medicinal forms of NG, their production is based on 1 -15% NG solutions in a vegetable (sunflower) oil or ethanol. NG solutions in ethanol are used for the fabrication of most medicinal preparations, while the oil solutions are used predominantly for the production of capsulated forms.Judging from the literature published, pharmacological investigations are devoted for the most part to the medicinal forms of NG, while works dealing with the properties of initial oil and ethanol solutions are virtually not available.NG is fully soluble in ethers, esters, acetone, and DMF, and exhibits a limited solubility in aliphatic alcohols [6]. For example, the NG solubility in ethanol at 20~ does not exceed 20 wt.%, while the solubility in vegetable oil is still not studied.The production, storage, transportation, and processing of NG solutions are performed in a broad temperature range (from-40 to +80~ Therefore, investigations of the stability of NG solutions in vegetable oil and ethanol are of great pra~cal importance.According to UN Recommendations [7], NG solutions with concentrations not exceeding 5% can be transported as readily inflammable fluids, while solutions concentrated above 10% should be carded as explosive substances. However, we believe that these recommendations are insufficiently substantiated and their observation leads to unnecessary expenditures. Determination of the explosive properties of NG was an additional part of our work.Initial materials. The solvents were commercial ethyl alcohol (State Standard GOST 5962-67), sunflower oil (GOST 1129-75), and acetone (GOST 2603-79). Nitroglycerin was synthesized as described in purified by passing it through a paper filter to remove the residual emulsified water. Effect of temperature on NG solubility in ethanol. A series of NG solutions in ethanol was prepared and a sample of each solution (10 + 0.2 g) was placed into an air-jacketed standard cell (Zhukov's device, GOST 18995.5-73). The cells were placed into an isopmpa~ol bath cooled at an average rate of 2.5 K/rain. The temperature of the solution in the cell was monitored with the aid of a thermoeouple and recorded on a chart recorder [8], and the phase state of the cell contents was visually observeeL The development of turbidity in the (initially transparent) solution indicated the phase separation of NG from ethanol. The temperature diagram exhibited a characteristic bending point; the intersection point of tangents drawn on the two sides of this point was used to determine the temperature of the NG phase separation. The average of two independent determinations was calculated and plotted versus the initial NG solution concentration (Fig. 1).Explosion test. The limited solubility of NG in ethanol hinders determination of the explosive properties of these solutions, because they are absolutely insensitive to mechanical or det...