Session: Advances in Mass Spectrometry:

In this study, a methodology is developed using high performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) to investigate the effect of instrumentation conditions on the analysis of degradation products from thermal aging of bis(2,2-dinitropropyl) acetal/formal nitroplasticizer (NP). NP is used with a polymeric binder to decrease mechanical sensitivity in high explosives while maintaining energetic potential. NP has been shown to degrade and generate reactive molecules, which contribute to the degradation of the polymer. To understand the mechanism of NP degradation, HPLC-MS/MS was used to identify molecular structures of degradation products. The configuration in our system includes a SCIEX EXION HPLC with high resolution tandem quadrupole time-of-flight mass spectrometers, SCIEX X500r Q-TOF. This method used electrospray ionization (ESI) in negative and positive modes (ESI+/ESI-). Since NP molecules have strong interactions with the HPLC-MS/MS system, they can potentially contaminate subsequent sample analyses. Therefore, an acetone rinse method was developed which effectively cleans any residual NP from the system, preventing cross-contamination between injections. Furthermore, to improve signal strength and prevent unnecessary alterations of the NP products, gradients of desolvation temperatures and of spray voltages were tested. With these optimizations, t he analyzed results successfully reveal experimental evidence of NP degradation in the condensed phase. This study demonstrates the analytic power of the HPLC-MS/MS for the identification of NP degradation products, helps us to verify and expand the currently proposed degradation mechanisms, and enables us to better understand the mechanisms of NP degradation under various aging conditions.

Camille H Wong

Post-Masters Research Assistant, Los Alamos National Laboratory

Appearances