5th Annual Snmmer Symposinm-Ingredients of Unknown Constitotion
ldent ificat ion of Complex Organic Materials By Mass Spectrometric Analysis of Their Pvrnlvsis Products PAUL D. ZEMANY General Electric Research Laboratory, Sc The ordinary analytical mass spectrometer is not adapted to the direct analysis of nonvolatile materials. Certain classes of materials may he pyrolyzed to give characteristic volatile decomposition products that may he analyzed in conventional mas8 spectrometers, and the records interpreted so as to identify the original material. In most cases very rapid heating of the sample gives the simplest decomposition products, which usually have obvious relationships with the original material. In the case of linear homopolymers, the monomer eomprises the hulk of the volatile material obtained by rapid, high temperature (above 800' C.) pyrolysis,
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NE of the outstanding advantages quoted for instrumental
methods of qualitative analysis is the fact that each substance gives an indication which is specific for that particular material (4). The most popular example is that of infrared absorption spectroscopy, where each compound has a spectrum as characteristic of itself as is the fingerprint of an individual (8).
Apparatus Used for Pyrolysis of Nonvolatile Materials lo. Eonfsining sample hholder with filament welded on and fa,.."ace in place pertly assembled *P
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while slor very coni]
of more c ples, the pyrolysis products may not all be identitled, but by standardizing the conditions of pyrolysis, characteristic mixtures are obtained whioh may he compared with known materials for charaeterization. Samples weighing a few tenths of a milligram are heated in vacuum after being coated on or placed inside the coils of standard receiving tube filaments. Some techniques that have pmved useful in the handling of the samples, in the pyrolysis, and in the interpretation of the results are deserihed.
In many Cases when dealmg with mixtures, the signal obtained from one substance is superposed an the signal given by all others as in x-ray absorption analysis (8, 15). When the signal can be measured as a. function of some parameter, the individual components may be often distinguished one from the other. Unfortunately, all these instruments have limitations as to what materials can be analymd by them, These limitations frequently have to do with the physical properties of the sample. In the case of mas6 spectroscopy, one requirement is that the compounds to be analyzed be capable of being ionized in the gas nhase. With materials volatile a t ordinary temperatures this requirement is easily met. With nonvolatile materials, methods of heating to raise the vapor pressure ( 1 1 ) or other methods ( 6 ) have been devised which extend the range of applioittion of the mass speotrometer. But Some materials cannot exist in the gas phase; polymers and biological materials, for example, decompose when they are heated before evaporating. It would seem that these materials are not suited for analysis by the mass spectrometer; however, as they do decompose on heating, one might hope that they would decompose in ohilracteristic fashion to give volatile decomposition products. The identity and relative amounts of the various products from a given material should dw&ys be the same, just as the identity and relative peak heights of the ions together are the fragmentation pattern of a compound in a mam spectrometer. If this is the case, then the mass spectrum, infrared spectrum,
