Reproducibility of PyMS

D.A. Hickman and 1. Jane, Reproducibility of PyMS using three different pyrolysis systems, Ana/tysf, 104 334-347 (1979). 

The MAB ion source offers several advantages over El for PyMS. By eliminating excessive fragmentation, characteristic of electron ionisation, and by producing highly reproducible mass spectra MAB (Kr) greatly simplifies the analysis of pyrolysis data. Furthermore, MAB ionisation, when combined to MS/MS, provides a useful tool for structural elucidation of pyrolysis products. The ability for selective ionisation can be very useful to reduce the background combination in techniques such as GC-MS, LC-MS or SFC-MS. 

Instrumental drift results from variations in the physical conditions of a pyrolysis mass spectrometer over time.127 It leads to variation in spectral fingerprints taken from the same material on different occasions. Short-term (<30 days) instrument reproducibility was examined by Manchester et al.57 who used PyMS to differentiate strains of Carnobacterium over a four-week period. Excellent reproducibility was obtained as separation of the five type strains was sustained and spectra did not change significantly over the four weeks. 

In a attempt to compensate for poor long-term reproducibility in a longterm identification study, Chun et al.128 applied ANNs to PyMS spectra collected from strains of Streptomyces six times over a 20-month period. Direct comparison of the six data sets, by the conventional approach of HCA, was unsuccessful for strain identification, but a neural network trained on spectra from each of the first three data sets was able to identify isolates in those three datasets and in the three subsequent datasets. 

The myriad of applications in diverse fields, coupled with the continuing advances in instrumentation, sensitivity, quantitative analysis, long-term reproducibility, and data-handling methods, will ensure that PyMS plays a crucial role in many analytical settings in the future. 

Fig. 2.40. Direct temperature-resolved (in-source) PyMS of PS/(BrxDPO, TBBP-A, Sb Oy) total ion current and mass chromatograms. After De Koster and Boon [725]. Reproduced by permission of Consumentenbond, The Hague.

Figure 14 In-source pyrolysis ammonia chemical ionization mass spectrum of cellulose, showing pseudomolecular ions [MNHJ of a series of 1,6-anhydro-oligosaccharides, ranging from the monomer (miz 180) to the dodecamer (miz 1962). The spectrum was obtained using a Pt-Rh filament probe and an E-B-type sector instrument. Reproduced by permission of Elsevier Science from Boon JJ (1992) Analytical pyrolysis mass spectrometry new vistas opened by temperature-resolved in-source PYMS. International Journal of Mass Spectrometry and Ion Processes 118/119 755-787.

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