Rapid and Simple Analysis of Trace Levels of Three Explosives in Soil by Liquid Chromatography-Tandem Mass Spectrometry

The analysis of trace levels of explosives in post-blast debris is critical in homeland security, environmental analysis, and crime scene forensic investigations. A fast and a selective determination method with high recovery was developed for the common explosives 2,4,6-trinitrotoluene (TNT), 3,5-trinitro-1,3,5-triazacyclohexane (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) in soil, using liquid chromatography-tandem mass spectrometry (LC-MS/MS). An easy and practical sample preparation method was developed using 4.00 mL acidified acetone with 0.25% HCl. After the easy evaporation of acetone extract, 10 min LC-MS/MS analysis provided a clear separation in column. Short duration of the whole procedure allows the use of this method in routine analysis. As a result of the analysis performed in spiked soils in 50.0, 100.0, and 250.0 ng g(-1) concentrations, high recoveries such as 100.4 (+/- 8.8)% for RDX, 96.9 (+/- 10.5)% for HMX, and 97.6 (+/- 13.9)% for TNT were obtained. Limit of detection (LOD) and limit of quantification (LOQ) values obtained from the analysis of the spiked soils were 4.3 ng g(-1) and 7.00 ng g(-1) for RDX, 6.8 ng g(-1) and 10.0 ng g(-1) for HMX, and 18.9 ng g(-1) and 38.0 ng g(-1) for TNT, respectively. The Horwitz Ratio (HorRat) calculation was used to evaluate if the inter-day and inter-analyst precisions were in the acceptable limits. The method was successfully applied to three artificial explosion samples for detection of explosives.