HMX and possible metabolites were separated using the same conditions as in the MRM method, with the exception of the gradient which was 0–5 min held at 80% A, decreasing linearly from 5 to 30 min to 50% A, decreasing linearly to 0% A from 30 to 60 min, and then holding for 5 min, before equilibrating to 80% A for
5 min. Source and gas parameters followed those in Eaton (2013). Final EMS data were analyzed using lightsight 2.0 (Applied Biosystems) and chemdraw ultra 12.0 (CambridgeSoft, Cambridge, MA) software to capture and interpret possible metabolites. LC-MS/MS analysis of ovine WRF samples showed near complete anaerobic degradation of HMX from 30 IDH inhibitor review to 5 μM at 24 h; autoclaved controls showed little change in HMX concentration over 24 h (Fig. 1). To identify metabolic products in HMX degradation by WRF, an enhanced mass spectrometry (EMS) scan was performed (Fig. 2). At 1 h, the HMX concentration had decreased to 22 μM and metabolite peaks consistent with an m/z of 149, 193 and 229 appeared (Figs 2c and 3). After 4 h, the HMX concentration decreased to 14 μM, while metabolite peaks consistent with m/z 149 and 193 increased and the peak consistent with an m/z of 229 showed a slight decrease. From 4 to 24 h, peaks consistent with m/z 193 and 229 continued to increase, while the peak consistent with m/z 149 decreased slightly
(Figs 2 and 3). At 24 h, EMS analysis showed a second, additional product consistent with an m/z of 149, which suggests ring cleavage from either
a reduction product or a hydroxylamino derivative of HMX (Fig. 4). Peaks visible after 40 min in Fig. 2 were found in the method high throughput screening blank in addition to samples, with the exception of peaks with an m/z of 227 and 241 at 52.5 and 53 min, respectively. Fluctuations in the occurrence of these possible metabolites were noted and will need further separation and analysis to clarify the chemical composition. Neither methylenedinitramine nor NDAB were detected in the MRM or EMS scans of the WRF microcosm samples. Overall, it appears that HMX degradation occurs more slowly in WRF than degradation of TNT (Fleischmann et al., 2004; Smith et al., 2008; De Lorme & Craig, 2009) or RDX (Eaton et al., 2011, 2013). Any toxic metabolites left Amoxicillin in the rumen beyond 20 h could be cause for concern if they were passed into the bloodstream and transported to fat, organs, and tissues. Thus, future studies should examine whether these HMX metabolites are toxic to the host ruminant. HMX displays mass spectrum fragmentation characteristics of both nitro compounds and nitrogen substituted cyclic amines. Using known fragmentation patterns of these classes of compounds, structures of detected metabolites were proposed and are shown in Fig. 4. Peaks at m/z149 and m/z 193 suggest ring cleavage through the mono-nitroso intermediate 1-NO-HMX, a reduction pathway proposed by Zhao et al.