Related Articles

• LC/MS: Identification of Unknowns by Combining Exact Mass Measurement with the NIST 02 Mass Spectral Database Similarity Search

  Electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI) tend to produce mass spectra with minimal fragmentation. Positive-ion mass spectra are dominated by protonated molecules and cation attachment, while negative-ion mass spectra usually show molecular anions or ions produced by hydride abstraction. However, by varying the potentials in the atmospheric pressure interface, collision-induced dissociation (CID) can produce mass spectra with extensive fragmentation. This is sometimes referred to as “in-source CID”. Because the ionization process and ion energies are different for ESI or APCI compared to electron ionization (EI), the fragmentation is often different from the EI mass spectra in common mass spectral databases. Furthermore, the fragmentation pattern can vary depending on in-source CID conditions. This leads one to question whether there is any value to searching an EI mass spectral database for ESI or APCI mass spectra. The NIST 02 Mass Spectral Search software provides functions for a structure similarity search. This search can be used to search the library for compounds with similar structures based on neutral losses, which is a more suitable method for searching ESI or APCI mass spectra against the library. Compounds that have mass spectra in the library database can often be identified from the search results. The similarity search can provide structural information about compounds that do not have mass spectra in the library by displaying the structures of similar compounds identified by the search.
• Structural Characterization of Polymers by MALDI Spiral- TOF Mass Spectrometry Combined with Kendrick Mass Defect Analysis

  High-resolution mass spectrometry (HRMS) continues to play an important role in the compositional characterization of larger organic molecules. In the field of polymer characterization, however, the application of HRMS has made only slow progress because of lower compatibility between matrix-assisted laser desorption/ionization (MALDI) and ultrahigh-resolution Fourier transform ion cyclotron resonance mass spectrometry (FT-ICRMS). In this study, a newly developed type of MALDI high-resolution time-of-flight mass spectrometry (TOFMS) with a spiral ion trajectory (MALDI spiral-TOFMS) was applied to the structural and compositional characterization of polymers. To create a graphical distribution of polymer components on a two-dimensional plot converted from complex mass spectra, we adopted a slightly modified Kendrick mass defect (KMD) analysis based on accurate masses determined using spiral-TOFMS. By setting the Kendrick mass scale based on the mass of the repeating units of a given polymer, components with common repeat units lined up in the horizontal direction on the KMD plot, whereas those components with different structures were shifted vertically. This combination of MALDI spiral-TOFMS measurement and KMD analysis enabled the successful discrimination of the polymer components in a blend of poly(alkylene oxide)s, the compositional analysis of poly(ethylene oxide)/poly(propylene oxide) block copolymers, and profiling of the end-group distribution of poly(ε- caprolactone)s synthesized under different conditions.
• “Remainders of KM” plot for polymers using msRepeatFinder: Intuitive display of High energy collision induced dissociation mass spectra acquired by SpiralTOF™/TOF

  Tandem mass spectrometry of polymer ions provides valuable information about the nature of individual end-groups, chain architecture (linear / cyclic / branched) and copolymeric microstructure. Using matrix-assisted laser desorption ionization (MALDI) with high energy collision-induced dissociation (HE-CID) tandem time-of-flight analysis (TOF/TOF) can be advantageous for MS/MS polymer analysis. However, the interpretation of the resulting mass spectrum may not be obvious when a number of ion series with low intensity signals are present. In this work, a “remainders of Kendrick mass” (RKM) analysis is used as a rapid post-acquisition data processing tool for TOF/TOF mass spectra in order to visualize and filter the ion series instantly via intuitive point alignments.
• Application of High-Resolution MALDI-TOFMS with a Spiral Ion Trajectory for the Structural Characterization of Free Radical Polymerized Methacrylate Ester Copolymers

  The structural characterization of copolymers by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS) remains a challenging task, since their random comonomer distribution creates very complicated mass spectra. In this study, a high-resolution TOF mass spectrometer with a spiral ion trajectory was applied to the structural and compositional characterization of free radical copolymerized poly(methyl methacrylate-co-tert-butyl methacrylate), poly(MMA-co-tBMA)s in ethyl lactate acting as a chain transfer agent. Virtually complete peak assignments of the isobaric components within the poly(MMA-co-tBMA)s served to identify the end-group combinations and copolymer compositions of individual copolymer components, allowing the distributions of comonomer compositions and six types of end-group combinations to be evaluated.
• Non-targeted analysis of electronics waste by comprehensive two-dimensional gas chromatography combined with high-resolution mass spectrometry: Using accurate mass information and mass defect analysis to explore the data

  Comprehensive two-dimensional gas chromatography (GC×GC) and high-resolution mass spectrometry (HRMS) offer the best possible separation of their respective techniques. Recent commercialization of combined GC×GC–HRMS systems offers new possibilities for the analysis of complex mixtures. However, such experiments yield enormous data sets that require new informatics tools to facilitate the interpretation of the rich information content. This study reports on the analysis of dust obtained from an electronics recycling facility by using GC×GC in combination with a new high-resolution time-of-flight (TOF) mass spectrometer. New software tools for (non-traditional) Kendrick mass defect analysis were developed in this research and greatly aided in the identification of compounds containing chlorine and bromine, elements that feature in most persistent organic pollutants (POPs). In essence, the mass defect plot serves as a visual aid from which halogenated compounds are recognizable on the basis of their mass defect and isotope patterns. Mass chromatograms were generated based on specific ions identified in the plots as well as region of the plot predominantly occupied by halogenated contaminants. Tentative identification was aided by database searches, complementary electron-capture negative ionization experiments and elemental composition determinations from the exact mass data. These included known and emerging flame retardants, such as polybrominated diphenyl ethers (PBDEs), hexabromobenzene, tetrabromo bisphenol A and tris (1-chloro-2-propyl) phosphate (TCPP), as well as other legacy contaminants such as polychlorinated biphenyls (PCBs) and polychlorinated terphenyls (PCTs).
• Structure analysis of a polymer additive using high-energy collision–induced dissociation mass spectra acquired by SpiralTOFTM/TOF

  Various kinds of additives are used in a polymer, such as an antioxidant, a light stabilizer, and an ultraviolet absorber. Because a polymer’s properties depend on the additives in the raw material, it is important to understand these additives. Matrix-assistance laser desorption/ ionization time-of-flight mass spectrometer (MALDI-TOFMS) JMS-S3000 SpiralTOF™ is widely used in polymer analysis. High-energy collision–induced dissociation (HE-CID) measurement with the TOF-TOF option is also useful in analyzing the structures of additives. SpiralTOF™ can achieve a high precursor ion selection with a revolution of 17 m. Fragmentation derived from HE-CID can be observed only due to the ions from post-source decay (PSD), these fragment ions can be eliminated by the four electrostatic sectors that constitute the spiral trajectory. In this Applications Note, we report on polymer structural analysis by compare fragmentation patterns in the product ion spectra of IRGANOX 1076 M+・ and [M+Na]+.