ASTM E2529-06
(Guide)Standard Guide for Testing the Resolution of a Raman Spectrometer
Standard Guide for Testing the Resolution of a Raman Spectrometer
SCOPE
1.1 This guide is designed for routine testing and assessment of the spectral resolution of Raman spectrometers using either a low-pressure arc lamp emission lines or a calibrated Raman band of calcite.
1.2 The values given in SI units are to be regarded as the standard.
1.3 Because of the significant dangers associated with the use of lasers, ANSI Z136.1 shall be followed in conjunction with this practice.
This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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Designation: E2529 − 06
StandardGuide for
Testing the Resolution of a Raman Spectrometer
This standard is issued under the fixed designation E2529; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope important for intercomparability of spectra obtained among
widely varying spectrometer systems, if spectra are to be
1.1 This guide is designed for routine testing and assess-
transferred among systems, if various sampling accessories are
ment of the spectral resolution of Raman spectrometers using
to be used, or if the spectrometer can be operated at more than
either a low-pressure arc lamp emission lines or a calibrated
one laser excitation wavelength.
Raman band of calcite.
4.2 Low-pressure discharge lamps (pen lamps such as
1.2 The values given in SI units are to be regarded as the
mercury, argon, or neon) provide a low-cost means to provide
standard.
both resolution and wave number calibration for a variety of
1.3 Because of the significant dangers associated with the
Raman systems over an extended wavelength range.
use of lasers, ANSI Z136.1 shall be followed in conjunction
4.3 There are several disadvantages in the use of emission
with this practice.
lines for this purpose, however.
1.4 This standard does not purport to address all of the
4.3.1 First, it may be difficult to align the lamps properly
safety concerns, if any, associated with its use. It is the
with the sample position leading to distortion of the line,
responsibility of the user of this standard to establish appro-
especially if the entrance slit of the spectrometer is underfilled
priate safety and health practices and determine the applica-
or not symmetrically illuminated.
bility of regulatory limitations prior to use.
4.3.2 Second, many of the emission sources have highly
dense spectra that may complicate both resolution and wave
2. Referenced Documents
2 number calibration, especially on low-resolution systems.
2.1 ASTM Standards:
4.3.3 Third, a significant contributor to line broadening of
E131 Terminology Relating to Molecular Spectroscopy
Raman spectral features may be the excitation laser line width
E1683 Practice for Testing the Performance of Scanning
itself, a component that is not assessed when evaluating the
Raman Spectrometers
spectrometer resolution with pen lamps.
E1840 Guide for Raman Shift Standards for Spectrometer
4.3.4 AnalternativewoulduseaRamanactivecompoundin
Calibration
place of the emission source. This compound should be
2.2 ANSI Standard:
chemically inert, stable, and safe and ideally should provide
ANSI Z136.1 Safe Use of Lasers
-1
Raman bands that are evenly distributed from 0 cm (Raman
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3. Terminology
shift) to the C-H stretching region 3000 cm and above.These
Raman bands should be of varying bandwidth.
3.1 Definitions—Terminology used in this guide conforms
to the definitions in Terminology E131.
4.4 To date, no such ideal sample has been identified;
however carbon tetrachloride (see Practice E1683) and naph-
4. Significance and Use
thalene (see Guide E1840) have been used previously for both
4.1 Assessment of the spectrometer resolution and instru-
resolution and Raman shift calibration.
ment line shape (ILS) function of a Raman spectrometer is
4.5 The use of calcite to assess the resolution of a Raman
system will be addressed in this guide. Calcite is a naturally
This guide is under the jurisdiction of ASTM Committee E13 on Molecular
occurring mineral that possesses many of the desired optical
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
properties for a Raman resolution standard and is inexpensive,
mittee E13.08 on Raman Spectroscopy.
Current edition approved Dec. 1, 2006. Published December 2006. DOI:
safe, and readily available.
10.1520/E2529-06.
4.6 The spectral bandwidth of dispersive Raman spectrom-
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
eters is determined primarily by the focal length of the
Standards volume information, refer to the standard’s Document Summary page on
spectrometer, the dispersion of the grating, and the slit width.
the ASTM website.
3 Field portable systems typically operate with fixed slits and
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. gratings and thus operate with a fixed spectral bandwidth,
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2529 − 06
FIG. 1 Calcite Raman Spectrum
while in many laboratory systems the slit widths and gratings 6.1.1 Measure the Raman spectrum of calcite using the
are variable. The spectral bandwidth of Fourier-Transform vendor’s recommended procedure for producing a Raman
(FT)-Raman systems is continuously variable by altering the spectrum of a sample with good signal to noise. The Raman
optical path difference of the interferometer and furthermore is spectrum of calcite is shown in Fig. 1. Because the Raman
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capable of obtaining much lower spectral bandwidth than most scattering of the 1085-cm band is polarized, the peak height
practical dispersive systems. Therefore, data obtained of a will depend upon the polarization of the laser and the location
narrow Raman band on a FT-Raman system can be used to of the sample with respect to the excitation laser. Rotate the
determine the resolution of a dispersive Raman system. A sample under excitation laser beam to obtain the maximum
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calibration curve of the full width at half height (FWHH) for signal from the 1085-cm band. The calibration relation
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the 1085-cm band of calcite as a function of spectral determined in 4.6 is:
resolution has been reported for this purpose. Measurement of
B ~cm ! 5 1.0209*S 10.684 (1)
w1085 resolution
this calcite band on a test dispersive instrument enables an
estimation of the spectrometer resolution.
Where:
4.7 Thisguidewilldescribetheuseofcalciteandpenlamps
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B = the measured bandwidth of the 1085-cm
w1085
for the evaluation of Raman spectrometer resolution for
CaCO Raman band, and
dispersive (grating based) Raman systems operating with a
S = the nominal resolution of the reference FT-
resolution
785-nm laser wavelength.
Raman spectrometer described in 4.6.
5. Reagents 6.1.2 After acquiring the Raman spectrum of the calcite
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sample, determine the FWHH of the 1085-cm band, B ,
w1085
5.1 Calcite
...
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