Capabilities of radiofrequency pulsed glow discharge-time of flight mass spectrometry for molecular screening in polymeric materials: positive versus negative ion mode
Negative ionization mode in the recent commercialized “PP-TOFMS, Plasma Profiling Spectrometer” instrument from Horiba has been examined in detail for the analysis of different polymeric materials and the results were compared with those of positive ion mode. Three compounds (tetrabromobisphenol A, tris-2-chloroethyl-phosphate and polytetrafluoroethylene) embedded in a polyurethane matrix were employed for such a purpose. Both, elemental information from the heteroatoms (F, Cl, Br and P) and/or molecular information provided, using either Ar or Ar + 4% O2 as discharge gases, were investigated. Also, the analytical potential of the negative ionization mode for integral speciation of polymers was explored, both in Ar and Ar + 4% O2. The screening of polymeric materials with similar elemental composition, in particular, four brominated flame retardants (BFRs), was performed to investigate this point. The results showed that elemental sensitivity for halogens in the negative mode of the instrument was higher as compared to positive detection. Sensitivity was observed to be directly dependent on the electron affinity of the analyte. Polyatomic information measured in negative mode using Ar as the discharge gas has demonstrated to be promising for a successful identification of the four different BFRs investigated. The adverse effects of reactions occurring in the plasma in the presence of oxygen have proved to be a serious drawback to be tackled for polymer characterization using this novel PP-TOFMS glow discharge-based technology.