High resolution triple quadrupole mass

The uptake of HRMS instrumentation into metabolite identification laboratories points to future developments and uses for these types of mass analyzers. From a hardware perspective, developments in TOF and Orbitrap technology will be needed to address lingering issues specific to these analyzers. In the TOF area, current commercial systems just coming to the market have addressed historical limitations of resolution, dynamic range, and mass accuracy. It remains to be seen if these specifications are sufficient or if further gains are needed. These instruments are not yet as sensitive as high-end triple quadrupole mass spectrometers, and improvements are needed in this area. For Orbitrap-based systems, the main limitations are scan speed and sensitivity. As... 

The most common types of MS/MS instruments available to researchers in food chemistry include triple quadrupole mass spectrometers and ion traps. Less common but commercially produced tandem mass spectrometers include magnetic sector instruments, Fourier transform ion cyclotron resonance (FTICR) mass spectrometers, and quadrupole time-of-flight (QTOF) hybrid instruments (Table A.3A.1). Beginning in 2001, TOF-TOF tandem mass spectrometers became available from instrument manufacturers. These instruments have the potential to deliver high-resolution tandem mass spectra with high speed and should be compatible with the chip-based chromatography systems now under development. 

Hughes, N., Winnik, W., Dunyach, J. J., Amad, M., Splendore, M., and Paul, G. (2003). High-sensitivity quantitation of cabergoline and pergolide using a triple-quadrupole mass spectrometer with enhanced mass-resolution capabilities. J. Mass Spectrom. 38 743-751. 

Both of the above examples illustrate that the sensitivity of the MDF method, in general, is comparable to PIS analysis and better than NLS methods (Figs 6.9 and 6.10). The sensitivity of the MDF method is attributed at least in part to the full-scan capability of high-resolution mass spectrometers such as the Q-TOF and LTQ-FTICR, which could be several times more sensitive than full-scan analysis by a triple-quadrupole mass spectrometer (Kostiainen et al., 2003). 

L. Yang, M. Amad, W.M. Winnik, A.E. Schoen, H. Schweingraber, I. Mylchreest, P.J. Rudewicz, Investigation of an enhanced resolution triple quadrupole MS for high-throughput LC-MS-MS assays. Rapid Coimnun. Mass Spectrom., 16 (2002) 2060. 

The introduction of the open-tubular columns eliminated the need for concentrating devices as the mass spectrometer pumping system could cope with the entire column eluent. Consequently, the column eluent could be passed directly into the mass spectrometer and the total sample can enter the ionization source. The first mass spectrometer used in a GC-MS tandem system was a rapid-scanning magnetic sector instrument that easily provided a resolution of one mass unit. Contemporary mass spectrometers have vastly improved resolution and the most advanced system (involving the triple quadrupole mass spectrometer) gives high in-line sensitivity, selectivity, and resolution. 

The MDS Sciex 4000 Q Trap, which is a triple-quadrupole instmment, has a mass range of m/z 5-2800 in Q1/Q3 RF/DC mode and has miz 50-2800 in the LQIT mode. The scan speed is user-settable from 250 Th/s, 1000 Th/s, and 4000 Th/s in LQIT mode with a maximum of 2400 Th/s in RF/DC mode. The mass resolution is >3000 at mIz 609 at 250Th/s. The LQIT from ThermoFisher Q-TQ XL) has three mass ranges from 15-200, 50-2000, and 200-4000 Th. The resolution is unit ( 2000 at m/z 1000) at the normal scan rate to 20,000 in the high-resolution scan mode (mass range not defined). See Tables 9.2 and 9.3 and Appendix Table A for mass accuracy and detection limits. 

For high-throughput analysis, it is important to increase the specihcity of each bioanalytical method. The enhancement of chromatographic resolution presents various limitations. Better selectivity can be obtained with TOF mass analyzers that routinely provide more than 5000 resolution (full width at half-mass or FWHM). The enhanced selectivity of a TOF MS is very attractive for problems such as matrix suppression and metabolite interference. In one report of quantitative analysis using SRM, TOF appeared less sensitive than triple quadrupole methods but exhibited comparable dynamic range with acceptable precision and accuracy.102... 

---