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Analysis of ADN, its precursor and possible by-products using ion chromatography

: Bunte, G.; Neumann, H.; Antes, J.; Krause, H.


Propellants, explosives, pyrotechnics 27 (2002), Nr.3, S.119-124
ISSN: 0340-7462
ISSN: 0721-3115
ISSN: 1521-4087
Fraunhofer ICT ()

In the last years ammonium dinitramide (ADN) appeared to be a promising new oxidator and a possible substitute for ammonium nitrate (AN) and especially for the chlorinated oxidizer ammonium perchlorate. Among other main advantages of ADN are to be mentioned the higher energy input combined with a reduced pressure in application. Furthermore, ADN shows no phase transitions like AN. For evaluating the purity of the synthesized and/or treated or aged pure or formulated ADN, the estimated ammonium nitrate content was taken into account. AN is known to be as well a by-product of the ADN synthesis as a possible decomposition product of ADN. Thermally treated ADN decomposes mainly to N2O, H2O, NO2 and AN which further reacts to N2O and NH3. Determining the nitrate contents assuming the rest being intact ADN must not lead to correct values especially in cases where ADN was treated/handled at higher temperatures in open systems. Concerning the technical scale synthesis of ADN, the precursor ammonium nitrourethane (ANU) must be eliminated in a quick but sufficient way needing a suitable analysis method for detecting nitrourethane besides nitrate and ADN. The objective of this work was to develop a suitable ion chromatographic method for the direct analysis of the anions concerned. Different ion exchanger phases were tested with organic and/or inorganic eluants. The ionic strength and flow rate of the eluant was improved to get an acceptable resolution for nitrite and nitrate combined with a short run time for the whole analysis. Detection was realized by electrical conductivity or UV absorption whereby the measurement wavelengths were optimized in order to get a small signal-to-noise ratio and simultaneously a suitable sensitivity especially for NO3- and nitrourethane. Under improved conditions (Ion Pac 11, 1 ml/min NaOH, 300 mmol), limits of detection (LOD) of 0.05 to 0.01 ppm were realized for NO3- and NO2-, respectively, measured at 214 nm. Using 220 nm as detection wavelength resulted in a LOD of about 0.3 ppm for nitrate. Using a wavelength between 210 and 220 nm results in a LOD for ANU of about 1 ppm. The linearity range for the analysis of DN- (285 nm) was found to be very broad (up to 700 ppm). All anions can be analyzed in one run taking maximally 30 minutes.