Sensitivity analysis HRMS

Mass spectrometry combines exquisite sensitivity with a precision that often depends more on the uncertainties of sampling and sample preparation than on those of the method itself. Mass spectrometry is a supreme identification and recognition method in polymer/additive analysis through highly accurate masses and fragmentation patterns quantitation is its weakness. Direct mass spectrometry of complex polymeric matrices is feasible, yet not often pursued. Solid probe ToF-MS (DI-HRMS) is a breakthrough. Where used routinely, mass spectrometrists are usually still in charge. At the same time, however, costs need to be watched. 

Quantitative Bioanalysis with High Mass Resolution Prior to the introduction of the API sources for LC-MS, GC-MS was the dominant format for mass spectrometry. Within GC-MS, mass analysis at high resolution using magnetic sector instruments was relatively common, especially in the central mass spectrometry facilities of major corporations and universities. Uses of these instruments included quantitation by GC-HRMS for improved specificity and sensitivity. 

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. 

HRMS is expensive and complex, and sensitivity is sacrificed for resolution. Rarely is enough of an aquatic pollutant, especially a pesticide residue, available for analysis by HRMS. However, advancements are rapid GC-HRMS analysis with on-line computer calculation of empirical formulae of each ion of each GC eluant (21) is now possible. Kearns (19) has discussed computer analysis of high resolution mass spectra. 

In general, ECNI-HRMS can provide higher sensitivity, whereas higher selectivity can be achieved using the EI-HRMS mode. This can be explained by the broad fragmentation pattern obtained with El, which allows one to chose a more specific ion to be monitored. Thus, both HRMS techniques may offer greater possibilities than LRMS for the analysis of toxaphene. 

As has been pointed out previously, HRMS can be used for the characterization and quantification of PCTs and toxaphene, but its application to routine analysis is difficult because of the high resolving power required, and the high cost of the instrumentation. EI-MS MS can be an excellent alternative to HRMS because of its high sensitivity and its lower cost. 

---