Its combination with a linear ion trap (LTQ-FT) has become a high end standard instrumentation in proteomic research, but a few
groups also use it in lipidomic research. The instrument’s hybrid character holds the possibility to run the linear ion trap and the FT-ICR-MS as two instruments in parallel, KPT-330 nmr resulting in high resolution precursor spectra and low resolution product ion spectra at an increased duty cycle. Coupled to HPLC, this experimental platform delivers retention time, exact sub ppm precursor masses and product ion spectra as means for identification (Figure 3). High mass accuracy paired with retention time is particularly helpful for identification of lipids with too little intensity for reliable fragment spectra. Such an integrated Inhibitors,research,lifescience,medical experimental platform is successfully used for quantitative determination of various lipid classes in lipid droplet preparations . MS/MS spectra are triggered
in a data-dependent manner on the four most intensive ions in the preview scan, resulting in MS/MS coverage of 66%. Owing to the ultra high resolving Inhibitors,research,lifescience,medical power and mass accuracy it is possible to confidently detect lipid species Inhibitors,research,lifescience,medical in crude lipid extracts at extremely low quantities, even when no MS/MS spectra are available for the precursor. Extension of reversed phase HPLC by a preceding HILIC fractionation of certain lipid classes results in higher sensitivity for lipid classes previously suppressed by PC. Other successful applications of similar instrumental setup are Inhibitors,research,lifescience,medical methods for quantitation of glycerophospholipids and TG in plasma samples  and for identification of glycerophospholipids in yeast . The disadvantages of such systems are their still rather slow duty cycle of about 3 s at 200,000 mass resolution, and the low mass cutoff in the linear ion trap, which might cause loss of some low mass diagnostic fragment ions. Figure 3 Workflow of a high resolution LC-MS Inhibitors,research,lifescience,medical platform relying on an LTQ-FT mass spectrometer. Full scan MS and MS/MS data are acquired parallel in data dependent acquisition
mode. Full scan MS data are automatically processed and quantified by Lipid Data Analyzer … Within recent years, orbitrap technology has started to replace the LTQ-FT. Originally Dipeptidyl peptidase designed for small molecule identification and quantitation, this technology has a lot of advantages in store for lipidomic applications, especially when hyphenated with the fragmentation power of linear ion trap or quadrupole technology. Although resolving power and mass accuracy are less than the LTQ-FT, they are still sufficient to provide unambiguous elemental compositions for most applications. Mass accuracy can even be increased into the sub ppm range by use of constant background signals as internal lock mass calibrants. The addition of an HCD quadrupole alleviates the low mass cutoff limitations of the LTQ and provides high resolution MS/MS spectra, although at a much slower speed than for example a quadrupole-TOF analyzer.