The use of emitters which have been activated at high temperature in Field Ionization and Field Desorption mass spectrometry offers some important advantages over the usual emitter type activated at room-temperature. Higher thermal stability of the microneedles is achieved and the emitters are extremely resistant to chemical attack. It becomes possible to induce a thermal fragmentation of solid compounds adsorbed on the emitter surface between room-temperature and approximately 2000°C. The field anodes may be re-used many times without loss of quality. The problem of mass references is solved in Field Ionization/Field Desorption-Mass Spectrometry when high temperature emitters are used. The Field Ionization mass spectra of perfluorokerosene (PFK) and perfluorotributylamine display peaks in the mass range between m/e 50 to 800, with a resolution of up to 30000 (10% valley definition). A short description of a rapid and easy activation to produce high temperature microneedles is given.The following abbreviations are used throughout this paper:-HT RT BAT HR MS EI FI CI FD High Temperature Room-Temperature Best Anode Temperature High Resolution Mass Spectrometry/Spectrum/Spectra Electron Impact Field Ionization Chemical Ionization Field Desorption I N T R O D U C T I O NSINCE the introduction of FD-MS of organic molecules" by Beckeyl there has been rapid and continuous development in the technique for the preparation of field anodes. This is because the emitter quality is of essential importance for the ion-yield and the achievement of detectable ion currents. Whilst the single-focusing instruments showed remarkable results in amino-acid chemistry and peptide ~e q u e n c i n g ,~.~ only one high resolution FD-MS study has been published to date.4 As the structure of the high temperature activated emitter is not changed at temperatures up to 2000°C5 and is not destroyed at higher field strengths (for example a total potential difference of 16 kV across a gap (d) of 0.5 mm field anode to cathode), this emitter type seems to be a basic requirement for a more widespread application A major aim in our research programme has been the utilisation of FD-MS for problems in cancer research. Specifically, the reaction between anti-tumour alkylating zgents or their metabolites and deoxyribonucleic acid (DNA) may be a principal cause of the cytostatic action of these compounds.0 In view of the importance of DNA in this field, the high resolution FD-MS of DNA components are being investigated. The * The term FD-MS denotes the technique where the field anode is dipped into a solution of a sample to be analysed.
885of FD-MS.
Field desorption (FD) enables mass-spectrometric investigation of large organic molecules without their vaporization. The present state of our theoretical understanding of the ionization of these molecules in the adsorbed state on organic emitters is described. The special problems of the technique and prospective developments in the apparatus for future analytical problems are outlined. The present progress report concentrates on analytical studies of biochemical model compounds and degradation products from environmental chemicals and drugs. The method is particularly suitable for the detection and identification of submicrogram quantities of underivatized polar substances present in complex mixtures or pre-purified extracts from biological materials. Anyeit. Chrm. inl~l'iiur Edil Vol 14 flY75i ' N o 6 414 Aiiqex. Chmm. blrernar. Edir. I Val. 14 ( 1 9 7 5 ) ' No. 6
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.