Determination of Dimethyl, Diethyl, and Dibutyl Phthalates in Small Arms Double-Base Propellants by Gas Chromatography

Rapid and accurate methods are proposed for the determination of dimethyl, diethyl, and dibutyl phthalates in small arms double-base propellants by GC. The phthalates are extracted from the propellant with méthylene chloride and an aliquot is passed through a silicone rubber SE-30 column at a temperature of 200°C for dimethyl and diethyl phthalates and 230°C for dibutyl phthalate. Triacetin is used as the internal standard in the determination of dimethyl and diethyl phthalates, while dimethyl sebacate is used as the internal standard in the determination of dibutyl phthalate. Dimethyl and diethyl phthalates can be determined on the same sample. None of the compounds found in ordinary small arms propellants interferes with the methods. Diphenylamine produces a peak that would interfere. However, it was found that nitroglycrein usually present in small-arms propellants containing phthalates decomposes in the injector and column, thus nitrating the diphenylamine and eliminating its interference.