Physico-chemical measurements of CL-20 for environmental applications: Comparison with RDX and HMX

CL-20 is a polycyclic energetic nitramine, which may soon replace the monocyclic nitramines RDX and HMX, because of its superior explosive performance. Therefore, to predict its environmental fate, analytical and physico-chemical data must be made available. An HPLC technique was thus developed to measure CL-20 in soil samples based on the US Environmental Protection Agency method 8330. We found that the soil water content and aging (21 days) had no effect on the recoveries (>92%) of CL-20, provided that the extracts were kept acidic (pH 3). The aqueous solubility of CL-20 was poor (3.6 mg l−1 at 25 °C) and increased with temperature to reach 18.5 mg l−1 at 60 °C. The octanol–water partition coefficient of CL-20 (log KOW=1.92) was higher than that of RDX (log KOW=0.90) and HMX (log KOW=0.16), indicating its higher affinity to organic matter. Finally, CL-20 was found to decompose in non-acidified water upon contact with glass containers to give NO2− (2 equiv.), N2O (2 equiv.), and HCOO− (2 equiv.). The experimental findings suggest that CL-20 should be less persistent in the environment than RDX and HMX.