Transition also multiple reaction monitoring

Formiminoglutamate (FIGLU), a marker for glutamate formimino-transferase deficiency, was recently also shown to be detectable by acylcarnitine analysis represented as a peak with m/z 287 (Fig. 3.2.3d) [64]. In poorly resolved acylcarnitine profiles, this peak may be confused with iso-/butyrylcarnitine (m/z 288). To avoid the incorrect interpretation of acylcarnitine profiles, we recommend performing the analysis in product scan mode as opposed to multiple reaction monitoring (MRM) mode. For example, the FIGLU peak at m/z 287 would not have been correctly identified in MRM mode because the transition of 287 to 85 is typically not selected. However, the 288/85 transition would reveal abnormal results, but in fact not represent either butyryl- or isobutyrylcarnitine, but another FIGLU related ion species. 

The use of a mass spectrometer as a detector for LC analysis brings a number of benefits to mycotoxin analysis. There is no need for chromophores or fluorophores in the analytes so derivatization can be avoided. The chemical structure of the analytes can be confirmed from molecular mass and fragmentation information and the use of tandem MS (MS/MS) allows greater selectivity. Multiple reaction monitoring and selected ion monitoring modes mean that chromatographic separation of all analytes is not necessary, as differentiation is carried out by the different ion transitions measured, and many multiresidue mycotoxin LC-MS methods now exist. These data acquisition modes can also increase the sensitivity of the method as the background noise is often reduced. 

Trace-level perchlorate analysis can also be done with IC-MS/MS. Three multiple reaction monitoring (MRM) transitions are usually monitored to quantify perchlorate in drinking water samples m/z 98.8/82.8),... 

---