Survey of Analytical Spectral Data Sources
is an increasing awareness the scientific community of the need for good, reliable technical information. This is evidenced by the buildup in recent years of information centers whose activities are designed to answer the specific needs of identifiable user groups employing bibliographic compilation systems. In many instances these systems are fully automated to provide quick access to the information required. I n addition to these types of systems there has been, since the early 1960’s, a resurgence of effort to extract and compile the physical science data contained in this body of literature. Sowhere is this more prevalent than in the analytical spectral area, where in recent years R large number of active groups have attempted to structure all types of spectral techniques into viable systems Iyhich respond to the scientific community’s needs. The effort is only beginning to realize its potential and has far to go in answering the demands being placed upon it. However, a start has been HERE
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made. and in some areas progress has been achieved. The intent of this paper is to discuss those spectral areas where emphasis has been placed on the compilation and evaluation of the numerical data extracted from the literature and to review what handling systems are employed and how they may be used to provide the answers constantly in demand. Everyone recognizes the value of good data. The more reliable the data, the less effort is required of the potential user in applying it to his problem. T h a t states the obvious! However, let’s look a t the history of analytical spectra and see what has happened over the years. Let’s admit that analysts in particular have always recognized the need for compiling reliable data as witnessed by such collections as Beilstein, Landolt-Bornstein, Gmelin, etc. However, since the tremendous leap forward in scientific effort dating from World W a r 11. the need to examine and characterize new materials has increased manifold. The technologies devel-
VOL. 114, NO. 7, JUNE 1972
oped during this 20-year period (195G70) also produced a host of n e x analytical tools permitting the analyst to work with both new and old materials in ever-decreasing concentration. These advances were utilized in the development of new chemical manufacturing processes. The process development engineer was called upon to design analytical instrumentation into his manufacturing process, permitting continuous surveillance of the materials being produced. If things went wrong, the analyst was frequently called upon to help unravel the problem of a bad batch of product. The increased focus by the scientist and analyst on these new capabilities revealed that the previous data lacked definition and in some instances \yere just plain vrong! Additionally, the new instrument a t ion ’ made it necessary for an entirely new set of measurement parameters to be conipiled; those anxious to take advantage of these new techniques either had to develop their own library-a rather costly pro-
REPORT FOR ANALYTICAL CHEMISTS
rnd Related Data Compilation Activities LEWIS H. GEVANTMAN Office of Standard Reference Data National Bureau of Standards Washington, DC 20234
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cess-or seek a reliable source which compiled the data of interest. The obvious step of going to the literature meant a n investment in time, and often as not, resulted in limited success. The accelerated production of data and its publication so flooded the scientific literature that the needed data were difficult to find and use. The problem, though not limited to analytical spectroscopy alone, was clearly enunciated in the 1963 Weinberg Report ( I ) and served to focus the attention of the scientific community on the need to act. The types of action taken to correct or alleviate these difficulties were many and varied and involved a large number of organizationsgovernmental, professional, and private-which were prime movers in the spectral data area. The Office of Standard Reference D a t a (OSRD) also played a key role in promoting and stimulating these activities. This role will become obvious to the reader as the various spectral data activities are described.
We will define a spectral data source as a group or organization which produces spectral data indexes and/or compilations, preferably evaluated, in a variety of formats for dissemination to the scientific user. We consider the issuance of bibliographic information on a continual basis as a qualified data source. The format used for distribution can be a replica of an original spectrum, a list of principal peaks or digitized values. It can be displayed on cards, microfiche-microfilm, magnetic tape, etc. The book or data sheet is also included in this definition, but the one-time publication of a book of compiled spectra is not considered as qualifying for this designation. However, its value to potential users is not dismissed. A number of such reference sources are listed in the Appendix. The following is a presentation of spectral data compilation activities broken down by spectral type. The activities described include not only the fully automated data compilation and evaluation center which
issues a variety of data products, but also the efforts of some scientific groups who are beginning to define the data needs in a specific area. A. Infrared Spectral Data Activities
1. Thermodynamics Research Center, B. 3. Zwolinski, Director, Texas A&M University, College Station, TX 77843. This first catalog of infrared spectral data was initiated in 1943 and sponsored by the American Petroleum Institute as Research Project 44. The source of this collection of spectra included academic, industrial, and governmental laboratories. The 6ubstances of interest are principally hydrocarbons of interest to the petroleum industry. However, hydrocarbon derivatives containing oxygen, nitrogen and sulfur, metallic hydrides, and some organometallic compounds, as well as some very common compounds, are also included. .4t a later date (1959) the Manufacturing Chemists Association's program on the publication of ir spectral data was started and op-
ANALYTICAL CHEMISTRY, VOL. 44, NO. 7, JUNE 1972
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erationally linked with the A P I project. The focus for substances covered was principally the nonhydrocarbons, as a complement to the A P I project. Spectra of organic compounds containing oxygen, nitrogen, sulfur, halogens, phosphorus, boron, arsenic, sodium, silicon, and zinc have been published without duplicating these compounds contained in the A P I file. The data are reported mostly in the range 2-15 p , but some in ranges 14-25 and 14-40 p. Percent transmittance is in most cases plotted against both wavelength in microns and frequency in reciprocal centimeters. Numerical values of principal peaks and shoulders are tabulated for some spectra. Data in the far infrared are also being collected. I n addition to the spectral curve, the name, molecular and semistructural formulas of the compound, and the solvent and concentration (if in solution) are given in the legend on the sheet. Spectra are selected from those submitted by contributing laboratories on the basis of the competence of the investigator, the quality of the instrumentation employed, and the purity of the compounds. Currently, emphasis is placed on grating spectra of high resolution. Indexes to the spectra are issued. 2. Sadtler Research Laboratories, Inc., Division of Block Engineering Corp., Philadelphia, PA 19104. This organization has issued infrared spectra since 1947. The substances analyzed include pure and commercial organic compounds, the latter including steroids, pyi-olyzates, monomers and polymers, agricultural and rubber chemicals, pharmaceuticals, and surface active agents. Infrared spectra are plotted as percent transmittance vs. wavelength in microns (range 2-15) and frequency in reciprocal centimeters. The name, molecular and semistructural formula, and boiling point or melting point or both are also given. The spectra are published on 8 1 / 2X ll-in. sheets. Prism spectra are displayed three spectra to a sheet, whereas grating spectra are displayed two to a sheet. Although every attempt is made t o certify compound purity and spectral accuracy, some spectra are 32A
not high quality. Sadtler Labs are now reviewing their entire collection and are actively engaged in updating and improving their quality. 3. Documentation of Molecular Spectroscopy, published by Butterworths & Co., Ltd., London, U.K., and Verlag Chemie, GmbH, Weinheim, Germany. The data are prepared by qualified experts in Britain and Germany under the direction of H. TIr. Thompson, Oxford University, and H. Kaiser, German Institute for Spectrochemie and Applied Spectroscopy, Dortmund. The substances covered include both organic and inorganic compounds selected by an advisory board. The source of the spectrum, compound, purity, etc., is given. Corrections to known errors are called to the subscriber’s attention by means of a newsletter. The infrared absorption spectra within the range 4000-200 cm-l (2.5-50 p ) are plotted against percent transmittance and percent absorption. Frequencies of the chief bands and their approximate intensities and peak absorption positions are indicated. Physical properties
ANALYTICAL CHEMISTRY, VOL. 44, NO. 7, JUNE 1972
(melting or boiling point, density, and index of refraction) and molecular and structural formulas are also given. DAIS spectral traces for organic compounds are reproduced on 53/4 x 81/4-in. rose-colored edgenotched cards. A coded classification is notched a t the top and a t one end of the card. It is based on three structural features: (1) the number of carbon atoms, (2) the basic skeleton, and (3) the substituent groups. An index to the DMS Card System, the DXIS-I-Cards, consisting of optical coincidence cards, 5 3 / 4 x 81/4 in., furnishes a means of rapidly obtaining all the spectral cards that have a given property (that is, a particular spectral feature or a particular structural characteristic). Spectral traces for inorganic compounds are reproduced on blue cards similar to the rose-colored cards, except that the coding is essentially stoichiometric. Bibliographic information is supplied on yellow cards for Volumes 1-6 (24 issues). Beginning with the 25th
Report for Analytical Chemists
issue (Vol 7, 1963), the literature cards have been replaced by a comprehensive literature list of papers on infrared, Raman, and microspectroscopy that have appeared in the same period. This list is accompanied by a set of I B l l sized optical coincidence cards known as the DAIS Junior Index. An author index is published yearly. 4. The Infrared Data Committee of Japan, T. Shimanouchi, Chairman, University of Tokyo, Tokyo, Japan. This group is a subcommittee of the Infrared and Raman Discussion Group whose membership includes the Chemical Society of ,Japan, the Spectroscopic Society of ,Japan, the Japan Society for Analytical Chemistry, the Pharmaceutical Society of Japan, and the Society of Polymer Science. Infrared spectra of organic compounds are presented in the range 4000-600 cm-l (2.5-16.0 p ) . The cards also give name of sample, empirical and semistructural formula, molecular weight, melting point, boiling point, refractive index, classification of the substance (e.g., steroid, alkaloid, hydrate),
and the type of skeleton (acyclic or type of cyclic). The strongest peak and several weaker peaks are indicated. Spectra are recorded on 5 X S i n . specially prepared slotted, edgenotched cards. I n addition to the spectral data, the date and temperature of measurement, type of spectrophotometer used, serial number, and reference of source are given. The spectra are examined and evaluated by members of the committee to ensure the publication of authoritative graphs. Care is taken to control the purity of the substance for which spectra are determined. When possible the compounds are purified by gas chromatography. The data cards are indexed in other literature collections. As an added note of interest, Professor Shimanouchi has authored three S S R D S publications on Molecular Vibrational Frequencies as listed: a. NSRDS-hTBS 6, “Tables of Molecular Vibrational Frequencies, Part 1,’’1967 ($0.40) b. iYSRDS-iVBS 11, “Tables of nlolecular Vibrational Frequencies, Part 2,” 1967 ($0.30) c. SSRDS-iYBS 17, “Tables of lllolecular Vibrational Frequencies, Part 3,” 1968 ($0.30) d . LYSRDS-LIrBS $9, “Tables of 3Iolecular Vibrational Frequencies,” (in press). This publication supersedes SSRDS-SBS 6, 11, and 17 mentioned above. e. “Tables of Molecular Vibrational Frequencies, Part 5.” This publication will appear as an article in the newly established Journal of Physical and Chemical Reference Data, Vol 1, Yo. 1, 1972. 5. Coblentz Society, President, James Scherer; Coblentz Society mailing address: 761 Main Avenue, Norwalk, CT 06851. A committee was established by the Society in 1957 to expedite the production and distribution of standard reference spectra. The source of supply for these spectra on pure compounds of commercial interest mas the membership of the Society. Infrared absorption spectrograms are issued with percent transmittance plotted against both wavelength in microns and wave number in reciprocal centimeters. For most, the range is 2-15 p , but for
some it is 2-30 p. The name, empirical or semistructural formula or both, and sometimes values of other properties, such as boiling point and refractive index, are given with each spectrum. The source of the spectrum is indicated. Four indexes are available: alphabetical, molecular formula, chemical classes, and numerical. The Chemical Classes Index each year gives a numerical listing of functional groups with a brief explanation of the type of function included in any group. When this collection reached a total of 4000 spectra, the Society changed its methods, and in partnership with ASTM and other organizations, focused first on the development and publication of criteria for exceptionally good (Research Grade) spectra. This was to be followed by the issuance of additional sets of spectra, each of which would conform to these criteria. The results of this effort are discussed later. 6. National Research CouncilNational Bureau of Standards Committee on Spectral Absorption Data, National Bureau of Standards, Washington, DC 20234. This collection of some 2000 compounds (spectra and properties) was compiled a t XBS with the cooperation and support of the National Research Council and American industry. The effort was terminated in 1962. -4lthough referenced in the ASTM index file, these spectra are no longer available for purchase. 7. American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA 19103. The ASTM has collected and indexed 92,000 infrared spectra drawn from existing collections, such as the older Coblentz Society files, the Japanese Data Committee, the Wyandotte Chemical Co., and others. Included are spectra published in scientific journals. The data base has been put on IBM cards and provides the same type of information described under the other spectral data sources. I t is appropriate at this point t o describe how this file has been indexed for ease of entry to the ir spectral data. I n addition to the spectral data cards, the ASTM and its volunteer workers have com-
ANALYTICAL CHEMISTRY, VOL. 44, NO. 7, JUNE 1972
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Report for Analytical Chemists
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pleted a heroic job of indexing these data on both I B M cards and on magnetic tape according to: a ) N o lecular Formula List of Compounds, Sames and References to Published Spectra; b ) Serial Number List of Compounds, S a m e s and References; and c) a computerized “SIRCH” system which enables one to seek identification of unknowns or obtain spectra rapidly for compounds of interest to the user. This last capability has been put to use by a number of organizations using the ASThI file as the basic data source: the D N A System of the Dow Chemical Co., Midland, 111, and the Singer Technical Services, Inc., S e w York City. In the case of the latter, a subscriber dials the computer from a teletypewriter and gives his password. The computer methodically asks for features of his data and scans the total file, including any confidential spectra the subscriber may have stored with the computer. The service is also available through the mail, TWX, and T E L E X . The DS-4 System is similar but a bit more advanced in its programmed approach to the use of the file. An improved version of the computer program (SIRCH 11) of the ASTM system is employed to attain unknown compound identification with a 90% accuracy per search. The Eastman Kodak Co., Rochester, N Y , has also constructed a similar file with both their own file of 10,000 spectra and the ASTM file ( 2 ) . Many reference books dealing with ir spectra are listed in the A p pendix. Most of these sources chould be used with some caution owing to the nonevaluated nature of the recorded data. B. Ultraviolet and Visible Spectra Data Activities
1. Thermodynamics Research Center, B. J. Zwolinski, Director, Texas A&M University, College Station, TX 77843. As in the case of ir spectra, both API and MCA uv spectra have been incorporated under the T R C project a t Texas L4&1t. The spectra on both organic and inorganic substances are produced as spectral curves giving absorbance vs. wavelength in angstrom units and frequency in reciprocal centi-
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ANALYTICAL CHEMISTRY, VOL. 44, NO. 7, JUNE 1972
meters, generally in the range 21005300 A . A table of wavelengths, slit widths, and optical densities (or absorbances) is given on the reverse side of a number of the early sheets. Sominal bandwidths in angstroms are indicated on the charts. Formula and state of the compound being measured are given. Most of the spectra issued since 1950 are reduced reproductions of original chart recordings obtained with the Beckman and the Cary spectrophotometers on continuous chart paper. Supplemental information is given in the legend. Two indexes are provided, one arranged by type of compound, the other by serial number. Contributing laboratories are identified in the indexes by code letters. T o upgrade quality, the project supplies contributors with detailed instructions that include recommendations for calibration and techniques to be used in obtaining and recording spectra with a number of acceptable commercial instruments. Operating characteristics are given such as temperature of measurement, cell length, and concentration and solvent if the substance is in solution or pressures if in the gaseous state. 2. Organic Electronic Spectral Data, Inc., J. P. Phillips, Treasurer, Department of Chemistry, University of Louisville, Louisville, KY. Organic Electronic Spectral D a t a , Inc., is a nonprofit group organized in 1957 by physical-organic chemists and others concerned about the state of ultraviolet literature. The organization is quite informal. Substances include organic compounds for which spectra have been published in the available journals. Wavelength values for maxima, shoulders, and inflections and the logarithms of the corresponding molar absorptivities of ultraviolet and visihle light are given. The primary purpose of this collection is to aid in compound identification. To be included the data have to meet minimum requirements. The compound must be sufficiently pure to permit a satisfactorv analysis and be definable by a molecular formula. In general, the solvent, or phase if not in solution, is given. However. some values marked “n.q.g.” are included if the
solvent is not given in the reference paper. The spectral data must be complete enough for the wavelengths of maximal absorption and molar absorptivities to be obtained if they are not given in the original publication. Wavelength values are given to the nearest millimicron unless the original data are given more precisely. Molar absorptivity values are given to the nearest 0.01 unit of log C. Coded references are given for all data. Abstract cards are also available. 3. Sadtler Standard UV Spectra, Sadtler Research Laboratories, Inc., 3316 Spring Garden Street, Philadelphia, PA 19104. This is a collection of spectra of compounds from the Sadtler collection. The spectra
are reported in the range from 200355 p. The molecular and semistructural formula and molecular weight are also given. The indexes to the Sadtler Infrared Spectra are applicable to the ultraviolet reference spectra, but ultraviolet alphabetical and numerical indexes are also published. The solvents used in sample preparation are important, as some bring out better resolution in scanning than others. Sadtler makes use of five solvents in a n order based on laboratory tests that showed minimum loss of energy with optimum solvent action. The spectra are scanned in acid, base, and neutral media. As many as four absorbance curves for solutions of various concentrations appear on each chart. S o criteria of purity are presented. Each spectrum measured is reviewed by consultants before publication. The method of preparation for scanning. cell thickness, concentration, wavelength of maximum absorbance, slit opening a t this wave-
length for each curve, and the instrument used are indicated for each spectrum. 4. Absorption Spectra in the u1traviolet and Visible Region, Dr. L. Lang, Budapest, XI, Budafoki ut 16-18, Hungary. The compilation "Absorption Spectra in the Ultraviolet and Visible Region" edited by L. L&ng is sponsored by the Hungarian Academy of Sciences. The original purpose of the compilers was to add the results of Hungarian research to previous foreign collections and to make available to foreign scientists previously unpublished spectra obtained in Hungary. Since the publication of Yo1 I, the publications have taken on an international aspect with spectra contributed from other countries. Substances include a wide variety of organic compounds, mostly in solution but a few in the solid or vapor phase, plus a small number of metal complexes and other inorganic substances. It is planned t o increase the proportion of medicinal compounds because of the increasing importance of spectroscopy in pharmaceutical research. Spectra are represented by graphs of log E ( E = extinction coefficient) vs. wavelength in millimicrons in the range 200-600 mp and in some cases to 800 mp. Observed values of log I o / I from which log E is bbtained are tabulated. D a t a for a given substance are often given in media of different pH as well as in different solvents. I n addition, associated data are given: structural and molecular formula, molecular weight, concentration and solvent if in solution, and melting and boiling point. Subject, formula, author, and figure (or diagram) are indexed. 5. The UV Atlas of Organic Compounds, Verlag Chemie, Weinheim/Bergstr., and Butterworths & Co., London, England. This Atlas is produced by the Documentation of Molecular Spectroscopy under the joint auspices described earlier. The Atlas presents selected ultraviolet absorption spectra of about 1000 organic reference compounds containing the most important organic chromophores. Among these are compounds containing multiplybonded C-atoms, C = 0 and C = S
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