ASTM E2529-06(2014)

Standard Guide for Testing the Resolution of a Raman Spectrometer

SIGNIFICANCE AND USE
4.1 Assessment of the spectrometer resolution and instrument line shape (ILS) function of a Raman spectrometer is important for intercomparability of spectra obtained among widely varying spectrometer systems, if spectra are to be transferred among systems, if various sampling accessories are to be used, or if the spectrometer can be operated at more than one laser excitation wavelength.  
4.2 Low-pressure discharge lamps (pen lamps such as mercury, argon, or neon) provide a low-cost means to provide both resolution and wave number calibration for a variety of Raman systems over an extended wavelength range.  
4.3 There are several disadvantages in the use of emission lines for this purpose, however.  
4.3.1 First, it may be difficult to align the lamps properly with the sample position leading to distortion of the line, especially if the entrance slit of the spectrometer is underfilled or not symmetrically illuminated.  
4.3.2 Second, many of the emission sources have highly dense spectra that may complicate both resolution and wave number calibration, especially on low-resolution systems.  
4.3.3 Third, a significant contributor to line broadening of Raman spectral features may be the excitation laser line width itself, a component that is not assessed when evaluating the spectrometer resolution with pen lamps.  
4.3.4 An alternative would use a Raman active compound in place of the emission source. This compound should be chemically inert, stable, and safe and ideally should provide Raman bands that are evenly distributed from 0 cm-1 (Raman shift) to the C-H stretching region 3000 cm-1 and above. These Raman bands should be of varying bandwidth.  
4.4 To date, no such ideal sample has been identified; however carbon tetrachloride (see Practice E1683) and naphthalene (see Guide E1840) have been used previously for both resolution and Raman shift calibration.  
4.5 The use of calcite to assess the resolution of a Raman system will be addressed in this guide...
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 stated in SI units are to be regarded as standard. No other units of measurement are included in this 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.  
1.4 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.

General Information

• Status: Historical
• Publication Date: 30-Apr-2014
• ICS: 71.040.50 - Physicochemical methods of analysis
• Technical Committee: E13 - Molecular Spectroscopy and Separation Science
• Drafting Committee: E13.08 - Raman Spectroscopy

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation: E2529 − 06 (Reapproved 2014)
Standard Guide 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 4. Significance and Use
1.1 This guide is designed for routine testing and assess- 4.1 Assessment of the spectrometer resolution and instru-
ment of the spectral resolution of Raman spectrometers using ment line shape (ILS) function of a Raman spectrometer is
either a low-pressure arc lamp emission lines or a calibrated
important for intercomparability of spectra obtained among
Raman band of calcite. widely varying spectrometer systems, if spectra are to be
transferred among systems, if various sampling accessories are
1.2 The values stated in SI units are to be regarded as
to be used, or if the spectrometer can be operated at more than
standard. No other units of measurement are included in this
one laser excitation wavelength.
standard.
4.2 Low-pressure discharge lamps (pen lamps such as
1.3 Because of the significant dangers associated with the
mercury, argon, or neon) provide a low-cost means to provide
use of lasers, ANSI Z136.1 shall be followed in conjunction
both resolution and wave number calibration for a variety of
with this practice.
Raman systems over an extended wavelength range.
1.4 This standard does not purport to address all of the
4.3 There are several disadvantages in the use of emission
safety concerns, if any, associated with its use. It is the
lines for this purpose, however.
responsibility of the user of this standard to establish appro-
4.3.1 First, it may be difficult to align the lamps properly
priate safety and health practices and determine the applica-
with the sample position leading to distortion of the line,
bility of regulatory limitations prior to use.
especially if the entrance slit of the spectrometer is underfilled
or not symmetrically illuminated.
2. Referenced Documents
4.3.2 Second, many of the emission sources have highly
2.1 ASTM Standards:
dense spectra that may complicate both resolution and wave
E131 Terminology Relating to Molecular Spectroscopy
number calibration, especially on low-resolution systems.
E1683 Practice for Testing the Performance of Scanning
4.3.3 Third, a significant contributor to line broadening of
Raman Spectrometers
Raman spectral features may be the excitation laser line width
E1840 Guide for Raman Shift Standards for Spectrometer
itself, a component that is not assessed when evaluating the
Calibration
spectrometer resolution with pen lamps.
2.2 ANSI Standard:
4.3.4 AnalternativewoulduseaRamanactivecompoundin
ANSI Z136.1 Safe Use of Lasers
place of the emission source. This compound should be
chemically inert, stable, and safe and ideally should provide
-1
3. Terminology
Raman bands that are evenly distributed from 0 cm (Raman
-1
shift) to the C-H stretching region 3000 cm and above.These
3.1 Definitions—Terminology used in this guide conforms
Raman bands should be of varying bandwidth.
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-
thalene (see Guide E1840) have been used previously for both
This guide is under the jurisdiction of ASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom-
resolution and Raman shift calibration.
mittee E13.08 on Raman Spectroscopy.
4.5 The use of calcite to assess the resolution of a Raman
Current edition approved May 1, 2014. Published June 2014. Originally
ԑ1
approved in 2006. Last previous edition approved in 2006 as E2529–06 . DOI:
system will be addressed in this guide. Calcite is a naturally
10.1520/E2529-06R14.
occurring mineral that possesses many of the desired optical
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
properties for a Raman resolution standard and is inexpensive,
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on safe, and readily available.
the ASTM website.
4.6 The spectral bandwidth of dispersive Raman spectrom-
Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
4th Floor, New York, NY 10036, http://www.ansi.org. eters is determined primarily by the focal length of the
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2529 − 06 (2014)
FIG. 1 Calcite Raman Spectrum
spectrometer, the dispersion of the grating, and the slit width. 6. Procedure
Field portable systems typically operate with fixed slits and
6.1 Calcite Calibration:
gratings and thus operate with a fixed spectral bandwidth,
6.1.1 Measure the Raman spectrum of calcite using the
while in many laboratory systems the slit widths and gratings
vendor’s recommended procedure for producing a Raman
are variable. The spectral bandwidth of Fourier-Transform
spectrum of a sample with good signal to noise. The Raman
(FT)-Raman systems is continuously variable by altering the
spectrum of calcite is shown in Fig. 1. Because the Raman
optical path difference of the interferometer and furthermore is -1
scattering of the 1085-cm band is polarized, the peak height
capable of obtaining much lower spectral bandwidth than most
will depend upon the polarization of the laser and the location
practical dispersive systems. Therefore, data obtained of a
of the sample with respect to the excitation laser. Rotate the
narrow Raman band on a FT-Raman system can be used to
sample under excitation laser beam to obtain the maximum
determine the resolution of a dispersive Raman system. A -1
signal from the 1085-cm band. The calibration relation
calibration curve of the full width at half height (FWHH) for
determined in 4.6 is:
-1
the 1085-cm band of calcite as a function of spectral
B ~cm ! 5 1.0209*S 10.684 (1)
w1085 resolution
resolution has been reported for this purpose. Measurement of
this calcite band on a test dispersive instrument enables an
Where:
estimation of the spectrometer resolution. -1
B = the measured bandwidth of the 1085-cm
w1085
4.7 Thisguidewilldescribetheuseofcalciteandpenlamps CaCO Raman band, and
S = the nominal resolution of the reference FT-
for the evaluation of Raman spectrometer resolution for
resolution
Raman spectrometer described in 4.6.
dispersive (grating based) Raman systems operating with a
785-nm laser wavelength.
6.1.2 After acquiring the Raman spectrum of the calcite
-1
sample, determine the FWHH of the 10
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
´1
Designation: E2529 − 06 E2529 − 06 (Reapproved 2014)
Standard Guide 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.
ε NOTE—Added title to Table 1 in August 2013.
1. 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 givenstated in SI units are to be regarded as the standard. No other units of measurement are included in this
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.
1.4 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.
2. Referenced Documents
2.1 ASTM Standards:
E131 Terminology Relating to Molecular Spectroscopy
E1683 Practice for Testing the Performance of Scanning Raman Spectrometers
E1840 Guide for Raman Shift Standards for Spectrometer Calibration
2.2 ANSI Standard:
ANSI Z136.1 Safe Use of Lasers
3. Terminology
3.1 Definitions—Terminology used in this guide conforms to the definitions in Terminology E131.
4. Significance and Use
4.1 Assessment of the spectrometer resolution and instrument line shape (ILS) function of a Raman spectrometer is important
for intercomparability of spectra obtained among widely varying spectrometer systems, if spectra are to be transferred among
systems, if various sampling accessories are to be used, or if the spectrometer can be operated at more than one laser excitation
wavelength.
4.2 Low-pressure discharge lamps (pen lamps such as mercury, argon, or neon) provide a low-cost means to provide both
resolution and wave number calibration for a variety of Raman systems over an extended wavelength range.
4.3 There are several disadvantages in the use of emission lines for this purpose, however.
4.3.1 First, it may be difficult to align the lamps properly with the sample position leading to distortion of the line, especially
if the entrance slit of the spectrometer is underfilled or not symmetrically illuminated.
4.3.2 Second, many of the emission sources have highly dense spectra that may complicate both resolution and wave number
calibration, especially on low-resolution systems.
This guide is under the jurisdiction of ASTM Committee E13 on Molecular Spectroscopy and Separation Science and is the direct responsibility of Subcommittee E13.08
on Raman Spectroscopy.
Current edition approved Dec. 1, 2006May 1, 2014. Published December 2006June 2014. Originally approved in 2006. Last previous edition approved in 2006 as
ԑ1
E2529––06 06. . DOI: 10.1520/E2529-06E01.10.1520/E2529-06R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E2529 − 06 (2014)
4.3.3 Third, a significant contributor to line broadening of Raman spectral features may be the excitation laser line width itself,
a component that is not assessed when evaluating the spectrometer resolution with pen lamps.
4.3.4 An alternative would use a Raman active compound in place of the emission source. This compound should be chemically
-1
inert, stable, and safe and ideally should provide Raman bands that are evenly distributed from 0 cm (Raman shift) to the C-H
-1
stretching region 3000 cm and above. These Raman bands should be of varying bandwidth.
4.4 To date, no such ideal sample has been identified; however carbon tetrachloride (see Practice E1683) and naphthalene (see
Guide E1840) have been used previously for both resolution and Raman shift calibration.
4.5 The use of calcite to assess the resolution of a Raman system will be addressed in this guide. Calcite is a naturally occurring
mineral that possesses many of the desired optical properties for a Raman resolution standard and is inexpensive, safe, and readily
available.
4.6 The spectral bandwidth of dispersive Raman spectrometers is determined primarily by the focal length of the spectrometer,
the dispersion of the grating, and the slit width. Field portable systems typically operate with fixed slits and gratings and thus
operate with a fixed spectral bandwidth, while in many laboratory systems the slit widths and gratings are variable. The spectral
bandwidth of Fourier-Transform (FT)-Raman systems is continuously variable by altering the optical path difference of the
interferometer and furthermore is capable of obtaining much lower spectral bandwidth than most practical dispersive systems.
Therefore, data obtained of a narrow Raman band on a FT-Raman system can be used to determine the resolution of a dispersive
-1
Raman system. A calibration curve of the full width at half height (FWHH) for the 1085-cm band of calcite as a function of
spectral resolution has been reported for this purpose. Measurement of this calcite band on a test dispersive instrument enables
an estimation of the spectrometer resolution.
4.7 This guide will describe the use of calcite and pen lamps for the evaluation of Raman spectrometer resolution for dispersive
(grating based) Raman systems operating with a 785-nm laser wavelength.
5. Reagents
5.1 Calcite and calcium carbonate (CaCO ) come in many forms. Iceland spar, from Iceland and, more commonly, Mexico, is
easily cleavable into a rhombohedron and is the clear crystal commonly found in retail stores. It is readily available and
inexpensive but may fluoresce under blue excitation. In addition, it is birefringent.
5.2 Low-pressure discharge emission (pen) lamps are widely available from optical supply companies. They are typically made
with noble gases or a metal vapor. Argon, krypton, and xenon pen lamps are applicable as resolution calibration sources for Raman
spectrometers operating with 785-nm excitation. These pen lamps cover a wide wave number range but have reasonably sparse
spectra.
6. Procedure
6.1 Calcite Calibration:
6.1.1 Measure the Raman spectrum of calcite using the v
...