RECEIVEDfor review May 12, 1975. Accepted July 14, 1975. This research was supported by a grant from the U S . Environmental Protection Agency, National Environmen-
tal Research Center, Atmospheric Aerosol Research Section, under Grant Number R802815.
I CORRESPONDENCE
I
Criteria for Infrared Spectra Submitted to Journals Sir: The quality of infrared spectra presented in the literature is variable and it cannot always be evaluated by inspection. Yet it is of great importance that such archival data be of sufficiently high quality to be useful in its intended context as well as for future reference. The purpose of these recommendations is to help ensure readable, reproducible spectra of sufficient accuracy to serve as documentation for the compounds scanned and as reference data for other users. Spectra that do not meet these minimum recommendations are open to serious questions as to their usefulness. These recommendations are based on more comprehensive criteria set forth by the Coblentz Society for evaluation of infrared spectra ( I ) . Instrumentation. Partial spectra may be used to illustrate specific points, but infrared reference spectra should extend a t least from 4000 to 650 cm-l with no more than minor gaps (marked) from mulling agents or solvents. Commercial spectrometers should be functioning a t manufacturer’s specifications. Instrument parameters (slit, scan speed, gain) should be chosen to ensure accurate servo response ( 2 ) . Data demonstrating instrument performance, especially abscissa accuracy, should be described. Abscissa accuracy should be at least f 5 cm-l from 4000 to 2000 cm-l and f 3 cm-l a t wavenumbers less than 2000 cm-l. Frequency calibration is best obtained from indene ( 3 ) ; polystyrene or H20 and CO2 (single beam spectrum) are marginally acceptable. Unbalanced atmospheric absorption bands, noise level, and dead spot from a sluggish servo should correspond to less than 1%T . The strongest absorption bands should extend approximately from 90% T to 5 or 10% T . Reduction of normal reference beam energy by more than 50%from mechanical attenuation, reflection attachments, reference sample absorption, or other experimental conditions should be avoided or dealt with by increasing the slit width or scan time using the well-known “trading rules” ( 2 ) .The transmission background a t 2000 to 1800 cm-I should be about 90% with a range from 75 to 100% acceptable. Sample Preparation. For most group frequency inter-
pretations, it is desirable to obtain spectra in inert solvents (CCl4-CS2) when possible. Cell path length and window material, concentration, and solvent used should be recorded. Mineral oil and fluorocarbon mulls are preferred when solid state spectra are needed. Pressed halide discs, if used, should be moisture free, and due cognizance taken of possible artifacts arising from grinding and pressing. A KBr matrix should not be used for HC1 salts because of possible halide exchange. Spectra of all purified end products and of key intermediates in a synthesis should be submitted. Spectra of any model compounds prepared for comparison are very useful. Other pertinent data such as elemental analysis and NMR or UV spectra should be included, along with the structures and approved names of the compounds. Format. Original spectra or glossy high-contrast photographic copies are needed for reproduction. Redrawn spectra are rarely acceptable for publication.
LITERATURE CITED (1) Coblentz Society Board of Managers, Anal. Chem., 38 (9), 27A (1966). (2) W. J. Potts, Jr., and A. L. Smith, Appl. Opt., 6, 257 (1967). ( 3 ) R . N. Jones and A. Nadeau, Spectrochim. Acta, 20, 1175 (1964).
Clara D. Craver’ Chemir Laboratories 761 W. Kirkham Avenue Glendale, Mo. 63122
Jeanette G. Grasselli’ Sohio Research 4400 Warrensville Center Road Cleveland, Ohio 44128
A. Lee Smith2 Dow Corning Corporation Midland, Mich. 48640 Member, Joint Committee on Atomic and Molecular Physical Data. Chairman, Joint Committee on Atomic and Molecular Physical Data.
RECEIVEDfor review July 10, 1975. Accepted July 10,1975.
ANALYTICAL CHEMISTRY, VOL. 47, NO. 12, OCTOBER 1975
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