Detection of Insensitive Munitions Using Blow Flies as Environmental Sampling Devices

Abstract

Insensitive munitions are high explosives that are less shock sensitive than historical high explosives. Munitions compounds 2,4-dinitroanisole, nitrotriazolone, and nitroguanidine commonly comprise the explosives. As the demand for insensitive munitions has increased, contamination from manufacturing sites and training ranges has also increased. Munitions compounds can seep out of soil into waterways, potentially impacting the environment and contaminating food and water supplies. Therefore, determining the presence of these compounds in the environment is important. Direct sampling by collecting soil and water samples can be difficult due to the need to collect samples over wide areas, sometimes in dangerous, remote, or access restricted areas. In this project, blow flies were used as environmental sampling tools to determine the presence of insensitive munitions in soil. In all fly experiments, blow flies were exposed to an insensitive munitions water-soil mixture. Three types of experiments were conducted: pooling multiple flies during extraction, feeding flies a protein-rich food source prior to munitions, and determining the persistence of munitions in blow flies after a one-time exposure. The amount of munitions present in flies was detected via high performance liquid chromatography-mass spectrometry. Reverse-phase and hydrophilic interaction liquid chromatography (HILIC) methods were developed to detect insensitive munitions. The reverse-phase method detected munitions in soil and blow flies immediately after exposure. However, ion suppression of compounds nitrotriazolone and nitroguanidine by glucose metabolites in aged flies limited the ability for detection with this method. A comparison of single blow fly and multi-blow fly extracts was done. Multi-fly extracts had increased signal to noise ratios, indicating method sensitivity improvement. The development of a HILIC method improved retention of the analytes impacted by ion suppression in reverse-phase liquid chromatography. However, separation of 2,4-dinitroanisole and its primary transformation product 2,4-dinitrophenol was not seen with this method. The HILIC method was used to determine persistence of IM in blow flies after controlled exposures to spiked soil. Blow flies were sampled at 0-, 1-, 3-, and 5-days post exposure at varying temperatures. 2,4-dinitroanisole/2,4-dinitrophenol was detected in flies one day post-exposure. Nitrotriazolone was detected in flies 3- days post feed. Nitroguanidine was detected 5 days post-exposure. This proof-of-concept project proved the ability to detect insensitive munitions in blow flies. Future directions of blow fly analysis include sampling blow flies baited from real-world contamination sites and development of a QuEChERS technique for improved detection from fly matrices.