Raman Shift Frequency Standards

The McCreery Group

Summary

The ASTM subcommitte on Raman spectroscopy has adopted eight materials as Raman shift standards (ASTM E 1840). Raman spectra of eight common chemicals were obtained by at least six different labs, with both FT and dispersive Raman spectrometers. For each of the standards, peak frequencies with standard deviations of less than 1 cm-1 were tabulated and are available for viewing. These peak frequencies have been established as an ASTM standard for calibrating the Raman shift axis of Raman spectrometers.

Procedure

1. Spectra of standards were determined by up to eight laboratories, as follows:
• FT-Raman, Bruker
• FT-Raman, Perkin-Elmer
• FT-Raman, Bio-rad
• FT-Raman, Dupont
• FT-Raman, Nicolet
• FT-Raman, Hercules
• Multichannel, EIC Laboratories
• Scanning (Spex 1403), Ohio State




2. Peak Raman shift frequencies were requested from each lab for several peaks in each standard spectrum, but the labs were "blind" and had no precise, prior knowledge of peak frequencies. In all cases, samples came from several different sources.
   
   
3. No calibration procedure was recommended. Each lab used the calibration procedure they already had in place.
   
   
4. Relative intensities are based on uncorrected spectra from the scanning system (Spex 1403 Scanning Raman Spectrometer, RCA 31034 PMT, 514.5 nm laser).
   
   
5. With the exception of a few values at low and high Raman shifts, only peak frequencies with standard deviations less than 1.0 cm-1 are reported.

Materials Used for Raman Shift Frequency Standards

1. naphthalene (Mallinckodt #94848)
2. 1,4 bis (2-methylstyryl) benzene (BMB) (Aldrich #25,740-0)
3. sulfur (Aldrich #41,498-0)
4. 50/50 (v/v) toluene/acetonitrile (Mallinckrodt Analytical Reagents)
5. 4-acetamidophenol (active ingredients of Tylenol) (Aldrich A730-2)
6. benzonitrile (Baker B883-07)
7. cyclohexane (Mallinckrodt Analytical Reagents)
8. polystyrene (Aldrich #18,243-5)