Tandem mass spectrometry Data-dependent scanning

It has been demonstrated also that the iTRAQ tandem mass spectrometric quantitative analysis strategy can be used in conjunction with the quadrupole ion trap by performing multiple stages of mass analysis (that is, MS ) [125], For example, chemical derivatization with the iTRAQ reagent not only labels the N-terminus of a peptide, but the lysine side chain also. Thus, tryptic peptides with a modified lysine residue present at the C-terminus will produce a yj product ion at m/z 291 following ClD-tandem mass spectrometry. To generate the low m/z iTRAQ reporter ions required for quantitation, the yj product ion is isolated and subjected to data-dependent CID-MS. Using this approach, peptide identification is achieved in the MS/MS scan, while quantitation is achieved via MS. ... 

Solid-phase extraction and liquid chromatography-tandem mass spectrometry are invaluable techniques for the determination of benzodiazepines and metabolites in biological matrices. The reason for using tandem mass spectrometry is to increase limits of detection without the need for chemical derivatization. Here we describe a technique for the detection of 26 benzodiazepines and metabolites at a detection limit of approximately 1-2 ng/mL in blood and 1-5 ng/mL in urine when screened using a data-dependent scan method. 

Liquid chromatography (LC)/ThermoFisher Scientific LTQ Ion Trap Mass Spectrometer or equivalent capable of tandem mass spectrometry and data-dependent scanning. 

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