Resolution and sensitivity

Like in all spectroscopic techniques resolution and sensitivity of the spectrometer determine the usefulness of an analytical technique and define the limitations of its application. 

Following Eq. 4 there are three different sources of line broadening adding to the natural line width AB, which reflects the lifetime of the final state (Heisenberg uncertainty principle) and in some cases an unresolved spin orbit splitting. In first approximation, 7) 

The non-monochromaticity of the x-ray photons results firstly from the finite width of the Is- and 2p-levels involved in the fluorescence process and then from the overlap of the Koj-Koj-spin doublet. Not considering the monochromatic UV-light 1S), Magnesium and Aluminium with a line width of 0.7 eV, resp. 0.9 eV proved to be most suitable as anticathode-material. 

A further improvement is possible with the help of an x-ray monochromator 29 30 , however, the inherent loss in sensitivity and the problems of probe adjustment create a number of difficulties which still have to be overcome in practise. Also the spectra obtained with the help of a monochromator clearly indicate that the gain in resolution for the test standard graphite is around 0.2 eV and the remaining 0.7 eV are obviously due to other parameters 30). 

On the other hand, the monochromator has the great advantage that it automatically eliminates the Ka3i4-satellites. Fig. 6 demonstrates that this can be achieved as well with the help of a Fourier transform filtering program, allowing a satellite free spectrum also for Magnesium irradiation where monochromatization with the help of a spherically bent quartz crystal so far has not been shown. 

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It should be noted that these results are only preliminary and have to be considered as a proof of concept. As is clear from eq. (2) the phase contrast can be improved drastically by improving the global resolution and sensitivity of the instrument. Currently, a high resolution desktop system is under construction [5] in which the resolution is much better than that of the instrument used in this work, and in which the phase contrast is expected to be stronger by one order of magnitude. 

For the highest resolution and sensitivity, laser-based spectrometers must be used. These have tire advantage that the resolution depends on the linewidth of the laser, rather than the monocln-omator. Furthennore, at any given moment, all of the power is at the frequency of mterest, rather than being spread out over the whole IR... 

The long-term stability of the nonaqueous coating films under elevated temperature and moderate humidity is reported to be better than aqueous coatings (30). Furthermore, color resolution and sensitivity of reacted nonaqueous coating films ate excellent. 

A number of devices suggest the possibiUty of improvement in the basic limitations of resolution and sensitivity for single-photon instmmentation. One device (24) employs an array of pinholes in a hemispherical shield that Hes inside a hemispherical soHd-state detector array. Simulations and initial experience using early models have suggested that the device could achieve a resolution in the brain of less than 3 or 4 mm and possibly as low as 1 mm. 

FT instruments of higher magnetic field strengths, providing greater spectral resolution and sensitivity... 

We can list the following areas as prime targets essential oil and natural product analysis, chiral analysis (e.g. of fragrances), trace multi-residue analysis, pesticide monitoring, and further petroleum products applications, in fact any separation where simply greater resolution and sensitivity is demanded-which means probably almost... 

Multidimensional (or eoupled) eolumn ehromatography is a teehnique in whieh frae-tions from a separation system are seleetively transferred to one or more seeondary separating systems to inerease resolution and sensitivity, and/or to reduee analysis time. The applieation of seeondary eolumns is illustrated sehematieally in Figure 8.1. The smaller the At, value applied, then the greater is the resolution and number of runs needed to eheek a eertain portion of the sample (5). 

For single-carbon-number AOS samples, analyses can be performed satisfactorily using just the GC method. For multicarbon-number AOS samples that have high sultone content (about 50 ppm), the LC method provides adequate resolution and sensitivity. However, for multicarbon-number AOS samples containing normal sultone levels and for AES samples, the combined LC-GC method is necessary to obtain the required separation and detection levels. Additionally, the combined method is advantageous in eliminating interferences in the LC method that are sometimes observed with AOS samples that have been bleached. 

In nanotechnology, dimensions of interest are shrinking from the fiva to the nm range. For many microelectronic devices, such as laterally structured surfaces, particles, sensors, their physical as well as their chemical properties are decisively determined by their chemical composition. Its knowledge is mandatory for understanding their behavior, as well as for their successful and reliable technical application. This presents a challenge for TOF-SIMS, because of its demand for the unique combination of spatial resolution and sensitivity. 

Recent developments in drug discovery and drug development spurred the need for novel analytical techniques and methods. In the last decade, the biopharmaceutical industry set the pace for this demand. The nature of the industry required that novel techniques should be simple, easily applicable, and of high resolution and sensitivity. It was also required that the techniques give information about the composition, structure, purity, and stability of drug candidates. Biopharmaceuticals represent a wide variety of chemically different compounds, including small organic molecules, nucleic acids and their derivatives, and peptides and proteins. 

Spectral width, dynamic range, resolution and sensitivity are expected to be pushed toward further limits. An emerging advancement in NMR spectroscopy is the DOSY technique (Section 5.4.1.1) which offers a separation capability as a function of the rates of steady state diffusion of molecules in solution. 

Tables 6.27 and 6.31 show the main characteristics of ToF-MS. ToF-MS shows an optimum combination of resolution and sensitivity. ToF-MS instruments provide up to 40000 spectra s-1, a mass range exceeding 100000 (in principle unlimited), a resolution of 5000, and peak widths as short as 200 ms. This is better than quadruples and most ion traps can handle. Unlike the quadrupole-type instrument, the detector is detecting every introduced ion (high duty factor). This leads to a 20- to 100-times increase in sensitivity, compared to QMS used in scan mode. The mass range increases quadratically with the time range that is recorded. Only the ion source and detector impose the limits on the mass range. Mass accuracy in ToF-MS is sufficient to gain access to the elemental composition of a molecule. A single point is sufficient for the mass calibration of the instrument. ToF mass spectra are commonly calibrated using two known species, aluminium (27 Da) and coronene (300 Da). ToF is well established in combination with quite different ion sources like in SIMS, MALDI and ESI.

LC-NMR can be operated continuously ( on-flow ) or discontinuously ( stopped-flow ). The optimum flow-rate in continuous-flow NMR is a compromise between best resolution and sensitivity. The sensitivity in NMR measurements has been increased significantly by ... 

The resolution and sensitivity of an imaging device depend on a number of variables, for example, spatial resolution in SPECT is limited primarily by collimator resolution. Typical gamma camera SPECT systems have in-plane spatial resolution in the final reconstructed image of about 12 mm for high-resolution imaging. Resolution and sensitivity in PET is given in Table 58-3. 

The interest in the dynamic operation of heterogeneous catalytic systems is experiencing a renaissance. Attention to this area has been motivated by several factors the availability of experimental techniques for monitoring species concentrations both in the gas phase and at the catalyst surface with a temporal resolution and sensitivity not previously possible, the development of efficient numerical methods for predicting the dynamics of complex reaction systems, and the recognition that in selected instances operation of a catalytic reactor under dynamic conditions can yield a better performance than operation under steady-state conditions. 

The m/z values of peptide ions are mathematically derived from the sine wave profile by the performance of a fast Fourier transform operation. Thus, the detection of ions by FTICR is distinct from results from other MS approaches because the peptide ions are detected by their oscillation near the detection plate rather than by collision with a detector. Consequently, masses are resolved only by cyclotron frequency and not in space (sector instruments) or time (TOF analyzers). The magnetic field strength measured in Tesla correlates with the performance properties of FTICR. The instruments are very powerful and provide exquisitely high mass accuracy, mass resolution, and sensitivity—desirable properties in the analysis of complex protein mixtures. FTICR instruments are especially compatible with ESI29 but may also be used with MALDI as an ionization source.30 FTICR requires sophisticated expertise. Nevertheless, this technique is increasingly employed successfully in proteomics studies. 

An added advantage of the spectra of MNP-d, adducts is that, since the lines are narrower than those of MNP adducts, much better signal-to-noise ratios are obtained for a given radical concentration, and the sensitivity of the method is correspondingly enhanced. Other attempts to obtain narrower spectral lines, and thus improve resolution and sensitivity, have been made. For example it was realized in some of the earliest work that 3-methyl-... 

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