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HANS D. BECKEY AND HIS CONTRIBUTION TO THE DEVELOPMENT OF MASS SPECTROMETRY
F. Röllgen
To cite this version:
F. Röllgen. HANS D. BECKEY AND HIS CONTRIBUTION TO THE DEVELOPMENT OF MASS SPECTROMETRY. Journal de Physique Colloques, 1986, 47 (C7), pp.C7-73-C7-74.
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JOURNAL DE PHYSIQUE
Colloque C7, supplement au n o 11, Tome 47, Novembre 1986
HANS D. BECKEY AND HIS CONTRIBUTION TO THE DEVELOPMENT OF MASS SPECTROMETRY
Institute of Physical Chemistry, University of Bonn, 0-5300 B o n n , F.R.G.
On June 8, 1986 Professor Hans D. Beckey, a pioneer in mass spectro- metry, whose work has been devoted to the development of field ioniza- tion mass spectrometry (FI MS) celebrated his 65th birthday. While this is normally the age of retirement of a German Professor, a serious disease had forced him to retire already in 1979 after more than two decades of active research. His scientific merits in the field of organic mass spectrometry were honoured on the occasion of his 60th birthday by a special issue of the International Journal of Mass Spectrometry and Ion Physics, and this year again a special issue of a journal (Organic Mass Spectrometry) has been devoted to him. Here I will briefly recall his achievements in the development of FI MS which had a strong impact on the progress of mass spectrometry.
In 1957 Beckey built his first FI source to apply FI MS to the detec- tion of free radicals in the gas phase. His previous research work was among other things related to gas phase reaction kinetics. Therefore, after reading the papers of Inghram and Gomer on the first use of an FI source in combination with a mass spectrometer, he suggested FI as a promising means for soft ionization and detection of free radicals, His first application of the new FI source combined with a magnetic single focusing mass spectrometer concerns cluster ion formation by FI of water and methanol. The chemistry and physics involved in field ion formation from molecules of adsorption layers were a major research objective in his group in Bonn for many years, revealing a new kind of surface chemistry.
Very early Beckey recognized FI to be a soft ionization technique for analytical organic mass spectrometry and the potential of this tech- nique for the analysis of mixtures. The typically low level of frag- mentation of molecules in FI mass spectra compared to EI spectra was first demonstrated for hydorcarbons. Up to now FI MS has been a tool for fast qualitative analysis of complex mixtures.
At the beginning, the low ionization efficiency obtained with tip emitters was a weak point of FI MS. Therefore, Beckey developed new types of FI emitters. Significant improvements were made by replacing emitter tips by thin wires, and by the introduction of the so-called emitter activation technique. In this technique field enhancing micro- needles are grown on the surface of wire anodes by field polymeriza- tion of organic compounds. This effect of a field induced needle growth was first observed for acetone and later on for a number of other compounds. In the present technique of activating wire emitters for mass spectrometry pyrographite microneedles are generated by expos- ing the wires to organic gases such as benzonitrile or indene to about
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1986713
C7-74 JOURNAL DE PHYSIQUE
1 5 0 0 K under FI conditions. The field induced growth of microneedles
under various conditions has been the subject of extended research work in Bonn over many years. Without the improvement of FI sources by emitter activation, FI MS probably would not have survived as an analy- tical technique.
In the FI mass spectra still obtained with tip emitters, Beckey dis- covered the effect of field dissociation of organic molecular ions. In a series of papers a theory of field dissociation was developed, pro- viding a thorough qualitative and even quantitative understanding of the effect of an external field on fragment ion formation. Field dis- sociation effects play a minor role with activated wire emitters compared to single tip emitters, but even with activated emitters depending on the type of compound, field dissociation can contribute to fragment ion formation (in addition to surface chemical effects) thereby providing structural information.
The usefulness of FI MS for the study of ultrafast unimolecular reac- tions in the ps time range was discovered again by Beckey and reported
in 1 9 6 1 . This method was unique in those days because no modern laser
techniques were available. The principles of this important method were systematically studied during the following years. The method was
later called "field ionization kinetics" (FIK). The development of this method with different types of ion sources, mass and energy analysers was almost entirely carried out in Bonn. Demonstrations of the potential of FIK for the measurement of rate constants, the study of the time evolution of mass spectra and the elucidation of structures of decomposing ions were also given. Since FIK provides a means of examining the current theories of mass spectra resulting from unimole- cular decomposition of ions, considerable efforts were made in his group in Bonn to compare the results of kinetic measurements with the predictions of the quasi-equilibrium theory of mass spectra. FIK tech- niques were applied in other laboratories as well and are still a valuable tool for gas phase ion chemistry studies.
The invention of "field desorption mass spectrometry" (FD MS) is the most important contribution of Beckey to analytical organic mass spec- trometry. In this technique solid samples are deposited on the surface of activated wire emitters from solutions and field desorbed by heat- ing the wire. The technique was introduced to perform soft ionization of sample molecules at temperatures below those required for volatili- zation and ionization of the molecules in the gas phase. The FD tech- nique was also introduced to enhance the ionization efficiency for organic solids. The successful use of FD MS for efficient and soft ionization of thermally labile and even non-volatile compounds has been demonstrated for samples from all areas of chemistry and bio- chemistry in numerous applications. FD MS has significantly extended the range of applications of analytical mass spectrometry in chemical, biological and medical sciences. It was the first of several ioniza- tion techniques to follow which are now used for soft ionization of non-volatile compounds directly from the solid or liquid state of samples.
The achievements and contributions of Beckey to the development of mass spectrometry cover a broad field, combining fundamental research, applied studies and technical developments. His outstanding scientific work is documented in a monograph on field ionization mass spectrometry and in about 1 6 0 publications.
