Symposium on Modern Methods of Analytical Chemistry L. T. HALLETT,Associate Editor
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government agency and of industrial concerns which were feed stock suppliers or producers of butadiene. A number of synthetic mixtures of hydrocarbons were prepared by the Phillips Petroleum Company and were analyzed by the cooperating members of the committee to determine how well a given laboratory checks its own analyses, how well various laboratories check each other, how precisely and accurately the varions gas components are determined, and the most suitable analytical methods. Analytical methods employed in the test program included lowtemperature distillation. infrared and ultraviolet absorption spectrometry, various chemical tests, and mass spectrometry. L4nalysis of over 8000 test results is in progress, and the preliminary conclusions are as follows: Individual laborat,ories were found to be able to check their own analyses, by any of the standard methods employed, with excellent. precision. On the average, a given laboratory can be expected to make determinations for most light hydrocarbon components of a gas with a probable error of 1 0 . 2 to 0.3 mole %. The extent to which laboratories check each ot.her is within values two to three times t,he probable error for a given laboratory. Each of the standard methods employed was found to have unique advantage with respect to accuracy and precision of measurement. The mass spectrometer method appears best, for determination of individual paraffin hydrocarbons, total butenes, and butadiene in high concentrations. The ultraviolet absorption spectra method is advanhgeous for but,adiene in low concentrations. Infrared absorption spectra measurements are best for isobutylene and individual n-butenes. Distillation and mass spectrometer methods show about the same accuracy and precision for total C I , total C,, and total Cj. Chemical methods show little, if any, advantage for specific olefin hydrocarbons. In general, methods are available for det'ermination of the main light hydrocarbon components with an accuracy of 0.3 mole % and a precision of 0.25 mole % (expressed as probable error). Methods developed and tested will be described along with detailed test, d a h in a book on light hydrocarbon analysis to be published by the Office of Rubber Reserve. Editors are 0. W. Burke of Rubber Reserve, F. D. Tuemmler of Shell Development, and Dr. Starr. An enlargement of test material summing the Rubber Reserve analytical test program will soon be offered for publication in .iSALYTICAL CHEHISTRY.
COUPREHEXSIVE review of the techniques and tools of present-day analytical methods by 12 experts featured the meeting held a t Louisiana State University February 2 to 5 . The symposium, organized by Philip K. West of the Department of Chemistry and Physics, attracted 200 from the southwest and other states. Besides the formal preqentations, the two informal round table discussions in the evening brought out the fact that research in analysis by competent analytical personnel is hecoming increasingly important. The analyst may be chemist, physical chemist, or physicist, depending upon the tools employed. Modern analysis requires the technician without formal college training to collect data and carry out routine, repetitious analysis, using well-designed instruments. I t is the function of the research analyst to interpret and co relate data and direct research on new methods. That such men should work as consultants an form part of the research team in the solution of problems was recognized as desirable and necessary. H. Laitinen, University of Illinois, covered the principles, theory, and application of the polarograph. The use of this method in inorganic analysis is well established, but it- use in the study of organic systems is a relatively nevi field in xvhich those with a good training in organic chemistry must pioneer. He said that the use of the polarograph for amperometric titrations is being eltended. A simple apparatus can be built for this method and it has the advantage over the potentiometric method that it can be carried out more rapidly, and also a suitable voltage can be selected best fitted for the system under study. Philip IT.Kest, in his paper on noninstrumental methods of of analysis, dealt briefly with chromatography of colored and noncolored systems, partition-chromatographv, and quantitative spot tests IT-hich are a method of applied chromatography. The use of complex ion formation to prevent interferences, to form distinctive products for colorimetric analysis, and in the establishment of desired formal potentials for electrometric methods wa3 discussed. The importance of organic reagents, catalytic reactions, and bioassays in analysis was covered. The reduction of methylene blue in the presence of selenium or its compounds is a strikingly simple but specific method for this element. Arthur L. Le Rosen, L.S.U., covered in some detail the need for standardization of chromatographic adsorbents and the demand by all those using this method for more fundamental knowledge. I n the analytical applications better adsorbents are required. Its value in qualitative as well as quantitative organic analysis was stressed. Philip J. Elving, Purdue University, and chairman of the A.C.S. Division of hnalytical and Micro Chemistry, discussed the most significant dcveloprnents in analytical chemistry during the past quarter cpntury. He pointed out that the trends during that period prove conclusively that analytical chcmistry covers a n ide field, which \vi11 necessitate changes in the teaching of this subject. The role of the analyst is a complex one, demanding a wide knowledge of science in general, together nith specialization in some particular branch of his interest and aptitude.
GENERAL APPLICATIONS OF MASS SPECTROMETRY
General applications of mass spectrometry was the subject of R. W.Thomas of the Humble Oil and Refining Co.: During t,he past, two years mass spectrometers of the type manufactured by Consolidated Engineering Corporat.ion and Westinghouse have been put into operation in the laboratories of the Baytown Humble Oil and Refining Company. Over 17,000 runs, including more t,han 12,000 analyses, have been performed on these instruments. Calibration data have been measured for over 145 pure gaseous and liquid compounds boiling up to 330' F. Although a major portion of the samples analyzed have been of a routine nature, considerable effort has been directed toward the development, of specialized t,echniques including (1) extension of mass spectrometer analyses to higher molecular weight hydrocarbons and other type compounds t,hrough use of high-temperature operations and internal standards, (2) use of a lowtemperature fract,ional condensation unit for concentration of trace components, and (3) rearrangement of the mass tube and electrical circuit,s to permit measurement of negative ions. This paper discussed data from these applications of mass spectrometry. Analyses were shown for five gaseous samples to illustrate the accuracy and reproducibility obtainable on mixtures of this type. Thcse result,s included determination of paraffins, olefins, and acetylenes in the C, to C5range, carbon dioxide, carbon monoxide, oxygen, nitrogen, and hydrogen. Trace component analyses were shown for a synthetic mixture in which the concent,rations of C2 to Cj paraffins were very small in comparison with the concentration of methane. The analyses also included determinat,ions for carbon dioxide, carbon monoxide, and nit,rogen, hydrogen, and helium. A special low-temperature fractional condensation unit in this type analysis was described. Results were shown for four liquid samples rvhich indicate
METHODS FOR ANALYSIS OF LIGHT HYDROCARBONS
C. E. Starr, Jr., Esso Laboratories, Baton Rouge, La., discussed the evaluation of analytical methods employed in the control and assay of feed stocks and product involved in the produrtion of butadiene, and the comprehensive test programs conducted by the Butadiene Committee on Specifications and Methods of rlnalysis for this purpose. This committee was organized under the sponsorship of the Reconstruction Finance Corporation's Office of Rubber Reserve and was composed of members of that 184
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applications of the mass spectrometers to two typical plant, control streams. The data included analyses of two synthetic mixtures simulating a cyclohexane concentrate stream containing benzene, n-hexane, t,wo C6 naphthenes, and six C, paraffins, and an aromatic stream containing cSto c9aromatics admixed &.ith paraffins and naphthenes. Liquid sample introduction procedures, high-kmperature operation of the mass spectromet,er tube and vacuum system, and the use of an internal standard for materials of high molecular weight were discussed. The production of negative ions by electron bombardment in the mass spectrometer and electrical circuit changes required for their detection and measurement was discussed. Xegative and positive ion abundance data and electron energies required for their production were shown for several compounds.
L. T. Hallett, General Aniline and Film Corp., discussed the type of personnel, organization, and training required in the solution of analytical problems. The importance of the integration of chemical research with research analysis was shown. Typical problems and methods for their solution were outlined, with emphasis on why false results can be obtained if a limited considapproach is used. The necessity of pure standards ered, together with the limitations of elementary analysis. Microtechniques were shown to be necessary in the solution of
Modern Instrumental Methods of Analysis
the spring meeting of the AVERICAN C H E J I I C SOCIETY. ~L The final program will be printed in Chemical and Engineering ,\-em for March 15.
-4 tentative program has bccn prepared for the Symposium on lfodern Instrumental Methods of Analysis, which is to be given under the sponsorship of the Minnesota Section of the AxER1c.m CHEJIICAL SOCIETY and thc Institute of Technology, 1-nivcrsity of llinncsota, at the Center for Continuation Study. Monday, March 22 General Instrumentation Methods. RALPH 1%.N ~ L L E R . General Optical Methods. E.J. LfEEHAS. 1\Iolecular Weight Determination by Light Scattering. 1’. DEBYE. Infrared Absorption Spectrometry. R . B. BARNES. Raman Spectra. E. J. R O ~ E X B A I W . Analytical Applications of Electron 1Iicroscopy. J. HILLIER.
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Tuesday, March 23 Use of Visible and Cltraviolet Spt,ctra in Analysis and Identification. R. K.Jones Polarography and Xniperometric Titrations. I. 11.KOLTHOFF. Mass Spectroscopic llethods. .I.0. C . SIER. Analysis by Emission Spectroscopy. J. R.CHI-RCHILI.. X-Ray Methods of Analysis. L. I
