Mass spectrography

The detection and determination of traces of cobalt is of concern in such diverse areas as soflds, plants, fertilizers (qv), stainless and other steels for nuclear energy equipment (see Steel), high purity fissile materials (U, Th), refractory metals (Ta, Nb, Mo, and W), and semiconductors (qv). Useful techniques are spectrophotometry, polarography, emission spectrography, flame photometry, x-ray fluorescence, activation analysis, tracers, and mass spectrography, chromatography, and ion exchange (19) (see Analytical TffiTHODS Spectroscopy, optical Trace and residue analysis). 

Francis W Aston Great Britain mass spectrography and discovery of isotopes... 

High mass resolution /h.r./f.i. mass spectrography was carried out using the same py. conditions as above. The photoplate (Q2, IIlford, England) was exposed to... 

Aston, with experience in chemistry as well as physics, began working at the Cavendish Laboratory in 1909 on separating isotopes using mass spectrography. He started to assist Thomson in his study on positive rays. Together they improved on Thomson s original apparatus. 

Analyses done by spark source mass spectrography. 

The base mixture is conveniently eluted through a silica gel column with chloroform/methanol, the fractions being detected by means of a UV light source. Preliminary mass spectrographie examination of the separated fractions is utilized to determine the identity, whether known or new, and the structural type (Section VII). 

Since that time the increasing sensitivity of analytical techniques (in particular, those of mass spectrography and gas chromatography) has enabled workers to show that The photooxidation of methyl iodide is complicated and a large number of reactions occur. 67 In fact,... 

A number of papers have appeared on the fragmentation of nitro compounds by mass spectrography. They were reviewed by Heynon [120] and recently by Khmernitskii and Terentiev [121] therefore only main outlines will be given here. Three main molecular ions have been found M NO " and M-... 

As already reported. Fraser and Paul examined nitrate esters, among them nitroglycerine, by mass spectrography (159). 

Trace Element Survey Analyses by Spark Source Mass Spectrography... 

The role of Spark Source Mass Spectrography (SSMS) as a high sensitivity trace element analytical method is discussed. The unparalleled combination of sensitivity and complete element coverage makes SSMS especially suitable for the analysis of liquid and solid materials involved in semiconductor processing. Sample requirements are discussed. The application of SSMS to semiconductor materials, process reagents, dopants, and metals, is Illustrated. Advantages and disadvantages of the technique as well as sensitivity and accuracy are discussed. 

Exactly twenty-three years ago this week a conference was held in Boston on ultrapurification of semiconductor materials. One third of the papers at that conference were devoted to Impurity analyses G). Spark source mass spectrography was the newest and most promising analytical technique available at the time, and I would like to compare the status of SSMS at that time to Its present status. 

Spark source mass spectrography is the most useful tool available to the microelectronics industiry for bulk trace level impurity analyses of a wide variety of materials. The technique routinely examines ciTTstal growth start materials, crucibles, finished crystals, dopants, solvents, metals and all substances used in microelectronics manufacture. 

M. Lounasmaa,9 of the Technical University of Helsinki. Otaniemi. Finland, refluxed for several hours a solution of 2,6-dimethoxy-l, 4-benzoquinone in acetic anhydride in the presence of sodium acetate, added water, and isolated by extraction with chloroform and crystallization from acetic acid a colorless product melting at 149-150° which, on the basis of analysis (C14H160 ). mass spectrography. and IR and N MR spectroscopy, was assigned the structure (6). 

In recent experiments mass spectrography has been used to identify 3-(2-hydroxy-4-chlorophenyl)-1,1-dimethylurea and 3-(2-hydroxy-4-chlorophenyl)-1 -methylurea in bean leaves as metabolites of monuron (Lee et al., 1973). This is, in the case of urea herbicides, experimental proof of the hydroxylating (oxidative) detoxication process, performed together with N-dealkylation by the microsomal oxidase enzyme system. 

These seven samples were examined in 14 different laboratories by infrared, ultraviolet and mass spectrography. The mass spectrographic results are the most revealing. Table 16-4 gives the distribution of molecular size in the various samples according to the number of carbon atoms in the molecule. These results were obtained from parent-peak data. The occurrence of pronounced maxima in the distributions shows resolution into fraction groups centered on four or five adjacent molecular sizes. 

Parent-peak mass spectrography cannot distinguish between a condensed polycyclic naphthene, e.g. 

TABLE 16-4. MOLECULAR SIZE DISTRIBUTION IN OIL FRACTIONS BY MASS SPECTROGRAPHY... 

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