Selectivity analysis high-resolution mass spectrometry

Two different sensitive and selective HS-SPME-GC/MS approaches for simultaneous analysis of TCA and TBA in wine using negative chemical ionization MS (GC/NCI-MS) and high-resolution mass spectrometry (GC-HRMS), were developed (Jonsson et al., 2006). Experimental conditions and performance of the methods are summarized in the Table 8.1. 

Selected ion chromatograms from an analysis of a sediment sample by gaoehromatography/high resolution mass spectrometry GC/HRMS... 

MSI offers a complementary technique as mass spectrometry can differentiate between various ions on the basis of their molecular weight. Additional selectivity is achieved by utilizing MS", high-resolution mass spectrometry, or orthogonal separation techniques, either separately or combined. Each additional stage of analysis serves to reduce the interfering chemical noise that originates from the tissue without tedious sample preparation. 

High resolution mass spectrometry offers high selectivity for the analysis of PCTs and toxaphene congeners in environmental and biological samples and avoids the specific internal interferences and the effect of environmental matrices. Both HRGC El MS and HRGC-ECNTMS in the SIM mode can be used as... 

While the chemiluminescence detectors have considerable selectivity for nitrosamines it must also be recognized that the possibility exists that any compound that can produce NO during pyrolysis will produce a signal (20). For example, TEA responses have been observed from organic nitrites, C-nitro and C-nitroso compounds (17,28) and nitramines (29). In the routine analysis of N-nitroso compounds, possible TEA analyzer responses to compounds other than N-nitroso derivatives normally do not represent a problem since the the identity of a compound can be readily established by co-elution with known standards on GC-TEA and/or HPLC-TEA systems (30-34). Additional confirmation could be provided when the sample can be chromatographed on both GC-TEA and HPLC-TEA (30,33). The technique accepted as the most reliable for the confirmation of N-nitrosamines is based on mass spectrometry (22, 35,36). Low-resolution mass spectrometry is satisfactory for the analysis of relatively simple mixtures and in those instances in which extensive clean-up of samples has been performed. However, complex samples require more sophisticated GC and MS procedures (e.g., high resolution-MS). 

Improvements in the instrumentation, ionization sources, high-resolution mass analyzers, and detectors [67-69], in recent years have taken mass spectrometry to a different level of HPLC-MS for natural product analysis. Mass spectrometry detection offers excellent sensitivity and selectivity, combined with the ability to elucidate or confirm chemical structures of flavonoids [70-72]. Both atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) are most commonly used as ionization sources for flavonoid detection [73-76]. Both negative and positive ionization sources are applied. These sources do not produce many fragments, and the subsequent collision-induced dissociation energy can be applied to detect more fragments. Tandem mass spectrometry (MS , n> 2) provides information about the relationship of parent and daughter ions, which enables the confirmation of proposed reaction pathways for firagment ions and is key to identify types of flavonoids (e.g., flavones, flavonols, flavanones, or chalcones) [77-80]. 

Nevertheless, the introduction of time-of-flight (ToF) analysers for SIMS analyses at the beginning of the 1980s, as well as the recent development of liquid ion sources delivering cluster projectiles now permit the analysis of organic materials with high sensitivity and selectivity. Moreover, thanks to its excellent lateral resolution (in the order of micrometres), and its minimal sample preparation, ToF-SIMS has become the reference technique for chemical imaging by mass spectrometry. 

---