Full scanning acquisitions

Due to their comparatively low costs and easy operation, quadtupole instruments are the most common instruments used for hyphenation in CEC analyses. However, these instruments only operate at low mass resolution. Sensitivity can be enhanced by operating in selected ion monitoring mode instead of full scanning acquisitions. Unfortunately, this leads to the loss of structural information. The expansion of biological applications has been largely accommodated by the TOE, quadtupole mass filter, and ion-trap instruments. The major advantage of TOE is its potential for speed, resolution, and good mass accuracy. 

LC-ISP-MS has been also successfully applied for the assay of 21 sulfonamides in salmon flesh (121). Separation was achieved in a reversed-phase LC system with gradient elution. Simple positive-ion spectra with an intense protonated molecule and no fragment ions of relevant abundance were displayed by all analytes by operating in the full-scan acquisition and SIM modes. Further application of tandem MS using SRM for increased sensitivity could overcome the lack of structural information presented by the ISP mass spectra. 

In lipid analyses with LC-MS, mass scanning methods have included MS full-scan acquisition with accurate mass, acquiring precursor and fragment exact mass data simultaneously with MSe scan, precursor ion scan and MRM. The most popular fragmentation method in MS/MS experiments has been collision-induced dissociation, but also higher energy collision dissociation has been utilized. 

Preliminary analyses were full-scan acquisitions with a mass range of 150-500 amu/2 sec. Electron multiplier voltage was set at 1500 V. Data were collected, analyzed and plotted with a Finnigan Superlncos data system. 

Figure 9 Full-scan acquisition mode of the quadrupole mass filter.

It is now possible to move on to discussion of general parameters of a mass spectrometer that are relevant to the selectivity-sensitivity compromise that is ubiquitous in analytical chemistry. Full scan acquisition mode refers to operation of a mass analyzer so as to acquire the entire spectrum of ions (or a major portion thereof) introduced into the analyzer. In the case of a pure compound, full scan mode delivers the maximum chemical information that the mass spectrometric experiment (MS or MS/MS) can... 

Figure 6.23 Illustration of an exainile of determination of appropriate ion time (IT) , i.e., trap fill time to minimize space charge effects in a MS full scan acquisition. The fast pre-scan is used to first estimate ion counts and this is compared with T, the target value for number of trapped ions suitable for the analytical scan. The ratio thus determined also fixes the ratio of ion fill times required to ensure that T ions are trapped for the analytical scan. Of course this assumes that the rate of ion introduction does not change between the prescan and the analytical scan fill time.

Dual Metabolic Profiles Using MS/MS TOTAL ION ELUTION PROFE E OF A CONTROL BLOOD SPOT Full Scan Acquisition of Acylcamitines and Amino Acids... 

By performing a full-scan acquisition in precursor ion mode it has been easy to realize that the prominent ion was at 287 Th and the 288 Th ion was just its C13-isotopomer, therefore avoiding to attribute the high level of the 288 Th ion erroneously to a C4 carnitine and consequently to an SCAD disorder. 

Two general modes of data acquisition are available in MS full-scan acquisition and selective ion monitoring (SIM). In full-scan analysis, a continuous series of mass spectra is acquired during the chromatographic run. For high-efficiency open capillary GC columns, sufficiently fast scanning is required in order to acquire a sufficient number of data points (typically 10 to 20) to adequately describe the chromatographic peak profile. However, in routine quantitative analysis of a limited number of components, better results in terms of lower detection limits are achieved by the use of SIM, in which the intensity of a (number of) ion(s) is monitored. The choice between full-scan and SIM acquisition in a particular application depends on the required detection limit and information content. 

Dwell Times t per Ion in Full Scan Acquisition with Ion Trap and Quadrupole MS Mass range 50 - 550 Da (500 masses wide), scan rate 500 ms ... 

The MS detection has been carried out using the BenchTOF-dx time-of-flight mass spectrometer for its sensitivity in the full scan acquisition mode. This allows recording of the complete mass spectra at similar levels to that of quadrupole... 

The full-scan acquisition mode, where a series of complete mass spectra is acquired as a function of time. 

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