Meetings sidered a variety of sample problems. With geological samples, steps must always be taken to ensure that the test sample truly represents the specimen collected in the field. Homogenizing techniques involving sample fusion were evaluated. In the analysis of an ion sample from its recorded mass spectrum, frequently only the number of singly charged ions of trace and matrix are measured. The ratio FT of singly charged to total number of trace ions may not equal FM the corresponding ratio for the matrix. Consequently, the ratio FT/FM must be included in the determination of the composition of the ion sample from its mass spectrum. As an alternative to polyethylene or rigid steel dies, the use of a naphthalene mold in an isostatic press for the preparation of pelletized powder samples was described. After pressing, the naphthalene is removed by sublimation, thereby minimizing interferences. Special techniques are required for microgram samples or highly radioactive powder samples. The sample may be pressed onto the end of a high purity gold wire, or as a solution or a liquid sludge, it may be deposited on a wire after which the solvent is evaporated. The fourth topic led by F. D. Leipziger (Kennecott Copper Co.) was concerned with electrical discharge type ion sources. A repetitive time-gated low voltage discharge type ion source was described. Among the advantages presented are stable ion current and consumption of cathode material only, except during the initial part of the pulse which is excluded in the time gating. With it, analysis precision is stated to be better than 5%. This ion source cannot be used with materials that are poor electrical conductors. Electrical detection was employed in a study of the influence of source parameters on the composition of the mass resolved ion beams using a radio frequency spark source. Tests indicate that the source parameters, in descending order of their importance, are accelerating voltage, spark displacement off instrument axis, spark gap, and duty cycle. With mass spectra recorded on ion sensitive plates, a correlation of ion transmission and mass line profiles was noted. Deviations from symmetrical profiles were most noticeable at low mass. Consequently, an adequate measure of the integrated ion intensity profile of the mass line is not obtained from the product of the peak intensity and half width. A questionnaire was distributed in an attempt to pool and correlate Relative Sensitivity Factors for different ma80 A
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ANALYTICAL CHEMISTRY
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we proclaimed last year, explaining that it represented the probability that any EASTMAN Organic Chemical you order will move out to you immediately from a local stock. Not a startling offer, really. It wasn't a cocky 100%, or a precise 99.999%. Not even 99%. Only j J J ' / o . Apparently it was good enough, though. Our production plant had to go on extra shifts. HO 1°^ m u s t have looked pretty good in comparison to general experience in the procurement of laboratory chemicals. In fact, the response to our promise was so strong that it became almost impossible to keep the promise! All turned out well. No longer are we afraid to repeat the promise:
98.1% And the list of stocking locations has grown If lacking a copy of EASTMAN Organic Chemicals List No. 44 a n d / o r its Cumulative Supplement 44-6, please inform Eastman Kodak Company, Eastman Organic Chemicals, Rochester, N . Y . 14650.
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trices, instruments, operating condi tions, and data handling techniques. This survey is sponsored by a Task Force of Subcommittee VII in the ASTM E-14 Conference on Mass Spec trometry. The fifth topic led by J. R. Woolston (RCA Laboratories) was a panel-type discussion of ion-sensitive plate prob lems. The effect of grain statistics on the precision of mass spectral photog raphy was reviewed. This led to the conclusion that for Q2 plates the opti mum precision is obtained in the range 30 to 70% optical absorption, and that for rectangular mass line profiles, the precision improves with increasing line width. "Trumpets" and "halo effects," the highly detrimental emulsion darkenings in the vicinity of strong mass lines, were discussed. In this context, the relative merits of developing the sur face image versus the internal image were presented. The reduction of this detrimental blackening by an electric ally conducting film above or below the emulsion was also described. Tests made on commercial ion-sensi tive plates and commercial developers tentatively indicated that the optimum detection sensitivity is obtained with Q2 plates presoaked and developed in ID 13 at 24 °C for three minutes. The properties and performance of gelatine-free ion-sensitive plates were described. These consist of a polycrystalline layer of contiguous domains 0.2 μτη thick. At low mass, they exhibit lower sensitivity, much shorter dynamic range and lower background than emul sions commonly used. Above m/e = 400, the gelatine-free plates have greater sensitivity and higher resolving power, indicating their usefulness for molecular spectroscopy. The last of the four half-day sessions was devoted to clinics by instrument makers for their own clients, general tours of NBS, and personal visits to individual laboratories. The open discussion of common prob lems and the free exchange of ideas that characterized this workshop was achieved in part by two conventions, first used at the corresponding 1967 NBS workshop—no photographing of slides would be done, and no one would be quoted directly. Hence, the anonym ity that permeates this account. A half-day workshop will be held during the "ASTM Committee E-14 Conference on Mass Spectrometry and Allied Topics meeting in Dallas on May 18-23, 1969. This will be similar in character to that held during the 1968 E-14 conference and again will be spon sored and organized by Subcommittee VII. VOL. 4 1 , NO. 2, FEBRUARY 1969
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