High-voltage techniques

Low-voltage electrophoresis is typically carried out at electric field strengths of 20 V/cm, while high-voltage techniques use field strengths of up to 200 V/cm.1... 

Fixed-product ion scans (sector instruments). High-voltage scan or linked scan at constant B /E. Both techniques give a spectrum of all precursor (parent) ions that fragment to yield a preselected product (daughter) ion. 

High voltage test techniques, for voltages higher than 1 kV 2071-1/1993 BS 921-1/1990 -... 

High voltage test techniques. Measuring systems 2071-1/1991 2071-2/1991 BS EN 60060-2/1997 ... 

Table 6.16 summarises the main characteristics of FI-MS. FT uses high voltages and was once restricted to sensitive double-focusing magnetic sector instruments of relatively high cost. Field ionisation is considered to be the softest ionisation mode. The reproducibility of the non-standard techniques, such as FI-MS and FD-MS, is less well assessed than that of EI-MS. A noticeable drop in FI use occurred after the mid-1980s because of the advent of FAB and other desorption/ionisation methods. FI-MS is only used in a few laboratories worldwide. 

Atom probe techniques have been used to investigate adsorption processes and surface reactions on metals. The FIM specimen is first cleaned by the application of a high-voltage field evaporation pulse, and then exposed to the gas of interest. The progress of adsorption and surface reaction is monitored by the application of a second high-voltage desorption pulse and a controlled time delay. 

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