Accelerating voltage scan

This procedure may only be applied by means of an additional relatively complex electronic unit of hi accuracy. The mass resolving power is not superior to that of the accelerating voltage scan (AVS), and the information on the energy release is lost. Therefore, the more simple scan mode, the AVS, is normally preferred for practical purposes. 

Fig. 8. Structure of the key ion at m/z 178 of bisamidin elucidated by DADI/MIKE spectrometry, accelerating voltage scan, accurate mass determination, and deuterium labelling ...

A similar type of analysis has been reported from envirornnental chemistry. Alkyl phthalates used as placticizers have become ubiquitous contaminants of our environment. In mass spectrometry, the prominent ion at m/z 149 generated fi-om phthalic acid ester plasticizers is well known. It may be used for the detection of all possible precursors by accelerating voltage scan. This type of mixture analysis was realized for common plasticizers . Obviously, the time required for the analysis is much shorter than that needed for a conventional analytical procedure. But here the... 

Accelerating voltage (high voltage) scan. An alternative method of producing a momentum (mass) spectrum in magnetic-deflection instruments. This scan can also be used, in conjunction with a fixed radial electrical field, to produce an ion kinetic energy spectrum. 

Figure 2. Repetitive scanning of m/e 310-330 (5 sec/scan). Standard conditions for this and all following figures ionizing voltage 70 eV, accelerating voltage 8 kV, trap current 300 /aA, multiplier 600, source 150°C.

Finally, the instrument can be operated in the peak-matching mode, which provides optimum mass resolving power and mass accuracy. Here the magnetic field strength is kept constant and the electric sector and acceleration voltages are scanned over a relatively small m/z range. This mode of operation is suitable when two ions that are very close in mass need to be separated or when the elemental composition of a molecule is to be determined at high resolution. 

Fig. 4 Scanning electron microphotographs of the surfaces of glassy carbon (GC) (a) and graphite epoxy composite (GEC) (b). The same acceleration voltage (10 kV) and the same resolution (100 and 10p.m) were used in both cases. Taken from [97]. Reprinted with permission...

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