Time-resolved mass spectrometry

Koy C, Miklcat S, Raptakis E, Sutton C, Resch M, Tanaka K, Glocker MO. Matrix-assisted laser desorp-tion/ionization-quadrupole ion trap-time of flight mass spectrometry sequencing resolves structures of unidentified peptides obtained by in-gel tryptic digestion of haptoglobin derivatives from human plasma proteomes. Proteomics. 2003 Jun 3(6) 851-8. 

Most ion-molecule techniques study reactivity at pressures below 1000 Pa however, several techniques now exist for studying reactions above this pressure range. These include time-resolved, atmospheric-pressure, mass spectrometry optical spectroscopy in a pulsed discharge ion-mobility spectrometry [108] and the turbulent flow reactor [109]. 

MS detection does not necessarily require as highly resolved GC separations as in the case of selective detectors because the likelihood of an overlapping mass spectral peak among pesticides with the same retention time is less than the likelihood of an overlapping peak from the same element. Unfortunately, this advantage cannot always be optimized because SIM and current gas chromatography/tandem mass spectrometry (GC/MS/MS) methods, it is difficult to devise sequential SIM or MS/MS retention time windows to achieve fast GC separations for approximately > 50 analytes in a single method. 

Current proteomics studies rely almost exclusively on 2D gel electrophoresis to resolve proteins before MALDI-TOF or ESI-MS/MS approaches. A drawback of the 2D gel approach is that it is relatively slow and work intensive. In addition, the in-gel proteolytic digestion of spots followed by mass spectrometry is a one-at-a-time method that is not well suited for high throughput studies. Therefore, considerable effort is being directed towards alternate methods for higher throughput protein characterization. 

The concept of peak capacity is rather universal in instrumental analytical chemistry. For example, one can resolve components in time as in column chromatography or space, similar to the planar separation systems however, the concept transcends chromatography. Mass spectrometry, for example, a powerful detection method, which is often the detector of choice for complex samples after separation by chromatography, is a separation system itself. Mass spectrometry can separate samples in time when the mass filter is scanned, for example, when the mass-to-charge ratio is scanned in a quadrupole detector. The sample can also be separated in time with a time-of-flight (TOF) mass detector so that the arrival time is related to the mass-to-charge ratio. 

Traditional methodologies such as 2D-gel electrophoresis and mass spectrometry have been considerably improved to resolve thousands of proteins in a single experiment. However, these approaches are both time consuming and unsuitable for the... 

Instrnments combining several analyzers in sequential order are very common. This combination allows mass spectrometry and mass spectrometry experiments (MS/MS) to be carried out. Modern MS/MS includes many different experiments designed to generate substructural information or to qnantitate componnds at trace levels. A triple quadru-pole mass spectrometer allows one to obtain a daughter ion mass spec-trnm resnlting from the decomposition of a parent ion selected in the first qnadrnpole. The MS/MS experiments using an FTICR or ion trap, however, are carried ont in a time-resolved manner rather than by spatial resolntion. 

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