Analytical resolving power

The analytical resolving power is applied in several analytical fields in form of well-known expressions such as, e.g., spectral resolving power Rx = X/AX or mass resolving power RM = M/AM. 

Estimated values of the analytical resolving power of several analytical methods as given in Eckschlager and Danzer [1994] are shown in Table 7.6. 

Table 7.6. Analytical resolving power Rz of several analytical methods...

The analytical resolving power can be interpreted as being the maximum number of signals which can find place within a given registration range. Therefore, it is evident that Rz is a measure of the multielement efficiency of analytical methods and influences strongly selectivity. 

Table 7.6 gives an overview about the analytical resolving power of various analytical techniques. 

FIGURE 6.6 (a) The 2D mobility-mass spectrum of 70 eV electron ionized carbon tetrachloride. (b) Mobility spectra for three selected ions, CCP (47 m/z), CClj (82 m/z), and CClj (117 m/z), taken at two different drift gas temperatures (298 and 103 K). At lower temperatures the mobility peaks narrow, leading to an increase in the analytical resolving power (denoted as R in b). Mobility spectra are extracted from the 2D data by integrating the ion current across an m/z window. 

Probably the simplest mass spectrometer is the time-of-fiight (TOP) instrument [36]. Aside from magnetic deflection instruments, these were among the first mass spectrometers developed. The mass range is theoretically infinite, though in practice there are upper limits that are governed by electronics and ion source considerations. In chemical physics and physical chemistry, TOP instniments often are operated at lower resolving power than analytical instniments. Because of their simplicity, they have been used in many spectroscopic apparatus as detectors for electrons and ions. Many of these teclmiques are included as chapters unto themselves in this book, and they will only be briefly described here. 

The classical polarizing light microscope as developed 150 years ago is still the most versatile, least expensive analytical instrument in the hands of an experienced microscopist. Its limitations in terms of resolving power, depth of field, and contrast have been reduced in the last decade, in which we have witnessed a revolution in its evolution. Video microscopy has increased contrast electronically, and thereby revealed structures never before seen. With computer enhancement, unheard of resolutions are possible. There are daily developments in the X-ray, holographic, acoustic, confocal laser scanning, and scanning tunneling micro-... 

Mass spectrometry is the only universal multielement method which allows the determination of all elements and their isotopes in both solids and liquids. Detection limits for virtually all elements are low. Mass spectrometry can be more easily applied than other spectroscopic techniques as an absolute method, because the analyte atoms produce the analytical signal themselves, and their amount is not deduced from emitted or absorbed radiation the spectra are simple compared to the line-rich spectra often found in optical emission spectrometry. The resolving power of conventional mass spectrometers is sufficient to separate all isotope signals, although expensive instruments and skill are required to eliminate interferences from molecules and polyatomic cluster ions. 

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