Ion transmission efficiency

As mentioned previously, the optimization of the ion transmission conditions to minimize H/D scrambling results in a three- to fourfold loss in ion signals. In the Synapt G2, the amount of sample is correlated to the signal intensity of the ETD ion fiagments [57] so to compensate for the loss of 

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The consequences of these boundary conditions strictly limit the secondary Ion transmission efficiency of the Instrument and thus, ultimately, the sensitivity of the analysis. 

Particularly for low-mass analytes, sector-based mass spectrometers used in a high-resolution mode can reduce spectral overlaps due to polyatomic ions, thereby improving detection limits compared to those of quadrupole mass spectrometers. However, ion transmission efficiency decreases significantly as the resolution is increased. For example, increasing the resolution provided by the sector mass spectrometer from 300 to 3000 reduces the ion transmission efficiency by about a factor of 14 [127], Further increasing the resolution to 7500 results in another order of magnitude loss in ion transmission efficiency [127]. The use of reaction cells may provide an alternative or complementary means to reduce background due to polyatomic ions. 

Models [105,177] and experimental measurements [178-180] suggest that the most severe chemical matrix effects are due to space charge induced decreases in the ion transmission efficiency from the plasma to the detector of the mass spectrometer. Unlike the deposition effects, these depend only on the composition of the sample being introduced into the plasma, not on previously run samples. 

ICP-MS can provide semiquantitative analysis for about 70 elements by using element response functions built into the instrument software and calibration of only a few elements [205,206]. Most elements are more than 90% ionized in the ICP (with the exception of elements with ionization potentials greater than about 8 eV). Ion transmission efficiency is a smooth function of mass. The natural isotopic abundances of the elements are well known. Therefore, it is possible to predict the relative sensitivities of the elements and any isobaric overlaps. 

However, the ion trajectories within the cycle may differ, causing differences of ion transmission efficiency and analytical resolution (5.2.2). 

ESI/APCI Mass Analyzer Dirty optics (not at maximum ion transmission efficiency). ... 

An ion transmission efficiency, defined as the ratio of the number of ions passing inside the mass analyzer inlet capillary, of about 0.9 was obtained with a laser spot displacement relative to the capillary central axis of 0.2 mm by switching off the extraction voltage 10 ps after the laser pulse [41],... 

Relative chemical potentials ion Transmission efficiency of ion source... 

Figure 2.11 Double-focusing setup (reverse Nier-Johnson geometry see below), illustrating how the dispersion of the first sector is compensated for by that of the second sector. Ions with the same mass-to-charge ratio, but a difference in kinetic energy and/or direction, are still focused to one point. Owing to the possibility of using a wider slit between the two sectors thus created, a lower loss in ion transmission efficiency is realized.

The ion transmission efficiency for the nuclide of mass m is the ratio of the measured to true amount of that nuclide, Kj= Hence the isotope... 

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