Extraction and analysis of trace amounts of cyclonite (RDX) and its nitroso-metabolites in animal liver tissue using gas chromatography with electron capture detection (GC-ECD)

An efficient extraction and cleanup technique, and an instrumental detection method suitable for determination of trace amounts of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and its nitroso-metabolites in animal liver tissue were developed and validated in this paper. The method includes the extraction of explosives from liver tissue samples using accelerated solvent extraction (ASE) followed by cleanup using florisil and styrene-divinyl benzene (SDB) cartridges to remove interfering naturally endogenous compounds. The instrumental analysis was conducted using a capillary column gas chromatograph coupled with an electron capture detector (GC-ECD). High recoveries (58.9-106.8%) of RDX, hexahydro-1-nitroso-3,5-dinitro-1,3,5-triazine (MNX), hexahydro-1,3-dinitroso-5-nitro-1,3,5-triazine (DNX), and hexahydro-1,3,5-trinitroso-1,3,5-triazine (TNX) were achieved at all concentrations studied. RDX, MNX, and TNX gave higher recoveries than DNX at all three tested concentrations (50, 250, 1250 ng/g). Overall recoveries of RDX, MNX, DNX, and TNX from 1 g beef liver samples containing 50, 250, and 1250 ng/g were 80.1, 82.8, 68.9, and 80.4%, respectively. The optimal injection port temperature range was 160-170 °C for analysis of RDX and its nitroso-metabolites. Higher or lower temperatures than 160-170 °C decreased signal amplitudes. RDX was unstable in the liver extraction matrix; as much as 50% of RDX was degraded 10 days after extraction if keeping the liver sample extracts at room temperature. Degradation of RDX to MNX, DNX, or TNX was not detected during the sample storage, extraction, or instrument analysis processes. Other optimized extraction and GC conditions are also discussed.