DETERMINATION OF PENTAERYTHRITOL TETANITRATE AND OTHER NITRIC ACID ESTERS WITH P-NITROANILINE AND AZULENE

During the hydrolysis of nitric acid esters, certain quantities of nitrite ions along with other products are produced. This effect is used for the quantitative determination of esters. In earlier publications (1, 2), we presented a micromethod, based on the determination of nitrite ions produced by hydrolysis for the determination of some esters. However, this method is not suitable for the determination of pentaerythritol tetranitrate because of its poor solubility in water and alcohol. Existing methods (3) were tried and found to be unsatisfactory also. This paper presents an application of Garcia's method (4) to the determination of some nitric acid esters (erythritol tetranitrate, pentaerythritol tetranitrate, and glyceryl trinitrate) and particularly of pentaerythritol tetranitrate in pharmaceutical preparations. The principle is as follows: nitrite ions produced by hydrolitic decomposition of esters under the influence of a strong base react with p-nitroaniline to form a diazonium ion, which is then coupled with azulene. The absorbance of the azo dye produced is measured at 515 nm. The method is rapid and sensitive and permits the determination of nitric acid esters in the concentration range of 5-50 µg in 10 ml of the reaction mixture. © 1969, American Chemical Society. All rights reserved.