Enhanced multiply charged

Enhanced multiply charged (EMC) RF only No fragment Trap/ scan... 

A QTRAP instrument is capable of a wide variety of scan modes full MS scan (MS), product ion scan (MS and MS ), PI scan, NL scan, MRM, predictive MRM (pMRM), multiple ion monitoring (MIM), enhanced multiply charged (EMC) scan and time-delayed fragmentation (TDF) (Hopfgartner et al., 2004 King and Fernandez-Metzler, 2006). Most of these scan modes can be incorporated into an IDA experiment to achieve metabolite detection and MS/MS spectral recording in a single run. 

The analysis for proteins present in plasma or a cell extract is a challenging task due to their complexity and the great difference between protein concentrations present in the sample. Simple mixtures of intact proteins can be analyzed by infusion with electrospray ionization and more complex ones by matrix assisted laser desorption ionization. MALDI is more suited for complex mixtures because for each protein an [M+H]+ signal is observed while for ESI multiply charged ions are observed. Surface enhanced laser desorption (SEEDI) is a technique for the screening of protein biomarkers based on the mass spectrometric analysis of intact proteins [49]. However in most cases for sensitivity reasons mass spec-... 

Electrostatic binding [11] may provide another very useful approach to preconcentration analysis. Enhancement of the redox ion concentration in the ion-exchange polymer volume should permit very sensitive analysis when combined with an appropriate electroanalyti-cal method [12,13]. However, the sensitivity of the ion-exchange equilibrium to the sample solution electrolyte composition and concentration and the necessity of having a multiply charged analyte ion may limit the usefulness of the electrostatic binding approach. 

Figure 3.12. Mass spectra of BSA digest obtained using a QTRAP with (bottom panel) and without (top panel) EMC scan function. In the bottom spectrum, all the singly charged background ions are removed to enhance the multiply charged ions from the BSA digest.

Enhanced cleavage at XXX-Pro is often observed in multiply charged ions. 

Corresponding to the FD spectra of the hydrochloride salts the m St intense ion in the spectra of the sulphate salts are the J c - Hjr and / C / ions. However, cluster ions and multiply charged ions are observed with strongly enhanced intensities. In Table 3 the characteristic singly charged ions in the FD spectra of the sulphate salts X - XVI are displayed. 

A proportional counter consists of a tube filled with a gas such as xenon, with positive and negative electrodes. The negative electrode is a thin wire maintained at a potential around -2 kV. Incoming photons ionise gas molecules. These drift towards the negative electrode, until the field enhancement around the thin wire is sufficient to multiply them by the cascade effect, and cause a charge pulse on the wire. The pulse is quenched by the addition of a quench gas, normally a halogen or hydrocarbon which reacts with the ions and stops the cascade. 

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