A NEW-TYPE OF GRAPHITE EMITTER FOR FIELD-IONIZATION FIELD DESORPTION MASS-SPECTROMETRY

A new type of field ionization/field desorption (FI/FD) emitter made of graphite is proposed. The method of emitter preparation is based on the observation that, on the fracture-surface of graphite, fine microcrystallites are exposed, the sharpness of which is sufficient to provide, under conditions of field mass spectrometry, field strength values sufficient for the ionization of molecules by a tunnelling mechanism. The ease of preparation and handling of such graphite emitters is noteworthy. The efficiency of the graphite emitters is illustrated by examples of FI/FD measurements of a number of substances with different physical and chemical parameters, producing M+., MH+, MCat+, Cat+, M(n)H+ types of ions. The main advantage of graphite emitters is seen as the possibility of precise control and direct measurement of the emitter temperature, which facilitates the obtaining of mass-thermograms of thermodegradation and the study of various temperature-dependent processes. Some specific potentialities of graphite emitters are outlined, namely the feasibility of direct analysis of organic inclusions in emitter material and switching to the surface-ionization mode.