QTOF values

With modern QTOF and Orbitrap mass spectrometers, mass resolution of 10" 10 with a mass accuracy within 5 ppm is routinely achieved. The advances in HRMS have not only provided accurate MS measurement but also signifieantly improved the specificity of LC—MS-based metabolite identification approaches in recent years (Tiller et al., 2008 Zhang et al., 2008a). For example, specificity of background subtraction in high-resolution full scanning is significantly improved. Current HRMS measures m/z values with precision at... 

MALDI-QTOF instraments basically follow an ion optical arrangement similar to that shown in Figure 2.16. The first quadrupole, Qo, is simply used to cool the ions kinetic energy and focus them onto the quadrupole axis so that they enter Qi with a well-defined initial trajectory, and is always used in RF-only mode. Qi is a mass-filtering quadrupole which can either be used in RF-only mode to pass a wide range of mass/charge values, or in mass-filtering mode to select particular... 

By connecting an ion mobility spectrometry (IMS) in front of a QTOF-MS, another dimension of separation is realized. Unseparated isobaric compounds, which have the same m/z value, can be separated after ionization by the structure-dependent drift time through the IMS. The combination of IMS with QTOF is also a powerful tool for nontarget analysis in complex samples, due to the fact that the chemical noise is drastically reduced by IMS. 

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