Raman Shift Frequency Standards
ASTM has established a series of Raman shift frequency standards (ASTM E 1840) for use in the calibrating of Raman spectrometers. Raman shift standards are easier to use than wavelength standards (such as atomic emission lines) and do not depend on laser wavelength. Standard Raman shifts for eight materials are included in the standard. The procedure is below and the standard spectra are available here.
The ASTM subcommittee 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.
- 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
- 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.
- No calibration procedure was recommended. Each lab used the calibration procedure they already had in place.
- Relative intensities are based on uncorrected spectra from the scanning system (Spex 1403 Scanning Raman Spectrometer, RCA 31034 PMT, 514.5 nm laser).
- 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.
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)
Raman Intensity Standards
Raman intensity standards were developed using both white light and luminescent standards for correction of Raman instrument response functions, as described in the following publications:
(1) Fryling, M.; Frank, C. J.; McCreery, R. L.; Intensity Calibration and Sensitivity Comparisons for CCD/Raman Spectrometers; Appl. Spectros. 1993, 47, 1965.
(2) Ray, K. G.; McCreery, R. L.; Simplified Calibration of Instrument Response Function for Raman Spectrometers Based on Luminescent Intensity Standards; Appl. Spectros. 1997, 51, 108.
(3) Frost, K. J.; McCreery, R. L.; Calibration of Raman Spectrometer Instrument Response Function with Luminescence Standards: An Update; Appl. Spectros. 1998, 52, 1614.
The National Institute for Standards and Technology has developed Standard Reference Materials using similar techniques, which are available for purchase. An example is SRM 2241 for 785 nm excitation: https://www-s.nist.gov/srmors/view_detail.cfm?srm=2241
Click here for the Overview of Modern Raman presented by Dr. McCreery at Pittcon 2009.