ASTM E1866-97(2007)
(Guide)Standard Guide for Establishing Spectrophotometer Performance Tests
Standard Guide for Establishing Spectrophotometer Performance Tests
SIGNIFICANCE AND USE
If ASTM Committee E13 has not specified an appropriate test procedure for a specific type of spectrophotometer, or if the sample specified by a Committee E13 procedure is incompatible with the intended spectrophotometer operation, then this guide can be used to develop practical performance tests.
4.1.1 For spectrophotometers which are equipped with permanent or semi-permanent sampling accessories, the test sample specified in a Committee E13 practice may not be compatible with the spectrophotometer configuration. For example, for FT-MIR instruments equipped with transmittance or IRS flow cells, tests based on polystyrene films are impractical. In such cases, these guidelines suggest means by which the recommended test procedures can be modified so as to be performed on a compatible test material.
4.1.2 For spectrophotometers used in process measurements, the choice of test materials may be limited due to process contamination and safety considerations. These guidelines suggest means of developing performance tests based on materials which are compatible with the intended use of the spectrophotometer.
Tests developed using these guidelines are intended to allow the user to compare the performance of a spectrophotometer on any given day with prior performance. The tests are intended to uncover malfunctions or other changes in instrument operation, but they are not designed to diagnose or quantitatively assess the malfunction or change. The tests are not intended for the comparison of spectrophotometers of different manufacture.
SCOPE
1.1 This guide covers basic procedures that can be used to develop spectrophotometer performance tests. The guide is intended to be applicable to spectrophotometers operating in the ultraviolet, visible, near-infrared and mid-infrared regions.
1.2 This guide is not intended as a replacement for specific practices such as Practices E 275, E 925, E 932, E 958, E 1421, or E 1683 that exist for measuring performance of specific types of spectrophotometers. Instead, this guide is intended to provide guidelines in how similar practices should be developed when specific practices do not exist for a particular spectrophotometer type, or when specific practices are not applicable due to sampling or safety concerns. This guide can be used to develop performance tests for on-line process spectrophotometers.
1.3 This guide describes univariate level zero and level one tests, and multivariate level A and level B tests which can be implemented to measure spectrophotometer performance. These tests are designed to be used as rapid, routine checks of spectrophotometer performance. They are designed to uncover malfunctions or other changes in instrument operation, but do not specifically diagnose or quantitatively assess the malfunction or change. The tests are not intended for the comparison of spectrophotometers of different manufacture.
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.
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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: E1866 − 97 (Reapproved2007)
Standard Guide for
Establishing Spectrophotometer Performance Tests
This standard is issued under the fixed designation E1866; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision.Anumber in parentheses indicates the year of last reapproval.A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope Ultraviolet and Visible Spectrophotometers
E387TestMethodforEstimatingStrayRadiantPowerRatio
1.1 This guide covers basic procedures that can be used to
of Dispersive Spectrophotometers by the Opaque Filter
develop spectrophotometer performance tests. The guide is
Method
intended to be applicable to spectrophotometers operating in
E925Practice for Monitoring the Calibration of Ultraviolet-
the ultraviolet, visible, near-infrared and mid-infrared regions.
Visible Spectrophotometers whose Spectral Bandwidth
1.2 This guide is not intended as a replacement for specific
does not Exceed 2 nm
practicessuchasPracticesE275,E925,E932,E958,E1421,or
E932PracticeforDescribingandMeasuringPerformanceof
E1683thatexistformeasuringperformanceofspecifictypesof
Dispersive Infrared Spectrometers
spectrophotometers. Instead, this guide is intended to provide
E958Practice for Measuring Practical Spectral Bandwidth
guidelines in how similar practices should be developed when
of Ultraviolet-Visible Spectrophotometers
specific practices do not exist for a particular spectrophotom-
E1421Practice for Describing and Measuring Performance
eter type, or when specific practices are not applicable due to
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
samplingorsafetyconcerns.Thisguidecanbeusedtodevelop
eters: Level Zero and Level One Tests
performance tests for on-line process spectrophotometers.
E1655 Practices for Infrared Multivariate Quantitative
Analysis
1.3 This guide describes univariate level zero and level one
tests, and multivariate level A and level B tests which can be E1683Practice for Testing the Performance of Scanning
Raman Spectrometers
implemented to measure spectrophotometer performance.
These tests are designed to be used as rapid, routine checks of
3. Terminology
spectrophotometer performance.They are designed to uncover
malfunctions or other changes in instrument operation, but do
3.1 Definitions—For terminology relating to molecular
not specifically diagnose or quantitatively assess the malfunc-
spectroscopic methods, refer to Terminology E131.
tionorchange.Thetestsarenotintendedforthecomparisonof
3.2 Definitions of Terms Specific to This Standard:
spectrophotometers of different manufacture.
3.2.1 action limit, n—the limiting value from an instrument
1.4 This standard does not purport to address all of the performance test, beyond which the spectrophotometer is
safety concerns, if any, associated with its use. It is the expected to produce potentially invalid results.
responsibility of the user of this standard to establish appro-
3.2.2 check sample, n—a single pure compound, or a
priate safety and health practices and determine the applica-
known,reproduciblemixtureofcompoundswhosespectrumis
bility of regulatory limitations prior to use.
constant over time such that it can be used in a performance
test.
2. Referenced Documents
3.2.3 level A test, n—a pass/fail spectrophotometer perfor-
2.1 ASTM Standards:
mance test in which the spectrum of a check or test sample is
E131Terminology Relating to Molecular Spectroscopy
compared against historical spectra of the same sample via a
E275PracticeforDescribingandMeasuringPerformanceof
multivariate analysis.
3.2.4 level B test, n—a pass/fail spectrophotometer perfor-
1 mance test in which the spectrum of a check or test sample is
This guide is under the jurisdiction of ASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom- analyzed using a multivariate model, and the results of the
mittee E13.03 on Infrared and Near Infrared Spectroscopy.
analysisarecomparedtohistoricalresultsforprioranalysesof
Current edition approved Dec. 1, 2007. Published December 2007. Originally
the same sample.
approved in 1997. Last previous edition approved in 2002 as E1866-97(2002).
DOI: 10.1520/E1866-97R07.
3.2.5 level one (1) test, n—a simple series of measurements
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
designed to provide quantitative data on various aspects of
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
spectrophotometer performance and information on which to
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. base the diagnosis of problems.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1866 − 97 (2007)
3.2.6 level zero (0) test, n—a routine check of spectropho- not possible, the user should recognize that the performance
tometer performance, which can be done in a few minutes, tests may not measure the performance of the entire instru-
designed to visually detect significant changes in instrument ment.
performance and provide a database to determine instrument 5.1.2 Data collection and computation conditions should
performance over time. generally be identical to those used in normal operation.
Spectraldatausedinperformancetestsshouldbedateandtime
3.2.7 optical reference filter, n—an optical filter or other
stamped, and the results of the tests should be stored in a
device which can be inserted into the optical path in the
historical database.
spectrophotometer or probe producing an absorption spectrum
which is known to be constant over time such that it can be
6. Samples Used for Performance Testing
used in place of a check or test sample in a performance test.
6.1 Thesampleusedforperformancetestingischosentobe
3.2.8 test sample, n—a process or product sample, or a
compatible with the spectrophotometer configuration, and to
mixture of process or product samples which has a constant
providespectralfeatureswhichareadequateforthetestsbeing
spectrum for a finite time period and which can be used in a
performed.
performance test. Test samples and their spectra are generally
6.1.1 The sample used for performance testing should
not reproducible in the long term.
generallybeinthesamephysicalstate(gas,liquid,orsolid)as
the samples to be analyzed during normal operation of the
4. Significance and Use
spectrophotometer.
6.1.2 The sample used for performance testing should be
4.1 IfASTM Committee E13 has not specified an appropri-
physically and chemically compatible with the samples ana-
ate test procedure for a specific type of spectrophotometer, or
lyzed during normal operation.
if the sample specified by a Committee E13 procedure is
6.1.3 The sample used for performance is chosen such that
incompatible with the intended spectrophotometer operation,
its spectrum is similar to the spectra which will be collected
then this guide can be used to develop practical performance
during normal operation.
tests.
6.1.4 The sample used for performance testing should have
4.1.1 For spectrophotometers which are equipped with per-
severalsignificantabsorbances(0.3
manent or semi-permanent sampling accessories, the test
thespectralrangeusedfornormaloperationofthespectropho-
sample specified in a Committee E13 practice may not be
tometer.
compatible with the spectrophotometer configuration. For
6.1.5 In order to adequately determine the photometric
example, for FT-MIR instruments equipped with transmittance
linearityoftheinstrument,thepeakabsorbanceforatleastone
or IRS flow cells, tests based on polystyrene films are imprac-
absorption band of the sample should be similar to and
tical. In such cases, these guidelines suggest means by which
preferablyslightlygreaterthanthelargestabsorbanceexpected
the recommended test procedures can be modified so as to be
for samples measured during normal operation.
performed on a compatible test material.
6.2 Check Samples—Check samples are generally used for
4.1.2 For spectrophotometers used in process
conducting performance tests. Check samples are single pure
measurements, the choice of test materials may be limited due
compoundsormixturesofcompoundsofdefinitecomposition.
to process contamination and safety considerations. These
6.2.1 Ifmixturesareutilizedaschecksamples,theymustbe
guidelines suggest means of developing performance tests
preparedinarepeatablemannerand,ifstored,storedsuchthat
basedonmaterialswhicharecompatiblewiththeintendeduse
the mixture is stable over long periods of time. In preparing
of the spectrophotometer.
mixtures, components should be accurately pipetted or
4.2 Tests developed using these guidelines are intended to
weighed at ambient temperature. It is recommended that
allow the user to compare the performance of a spectropho-
mixtures be independently verified for composition prior to
tometeronanygivendaywithpriorperformance.Thetestsare
use.
intended to uncover malfunctions or other changes in instru-
6.2.2 While mixtures can be used as check samples, their
ment operation, but they are not designed to diagnose or
spectra may be adversely affected by temperature sensitive
quantitatively assess the malfunction or change. The tests are
interactions that may manifest themselves by wavelength
not intended for the comparison of spectrophotometers of
(frequency) and absorbance changes.
different manufacture.
6.3 Test Samples—A test sample is a process or product
sample or a mixture of process or product samples whose
5. Test Conditions
spectrum is expected to be constant for the time period it is
5.1 Whenconductingtheperformancetests,thespectropho-
used in performance testing.The test sample must be stored in
tometer should be operated under the same conditions as will
bulkquantitiesincontrolledconditionssuchthatthematerialis
be in effect during its intended use. Sufficient warm-up time
stable over time.
should be allowed before the commencement of any measure-
6.3.1 Since test samples are often complex mixtures which
ments.
cannot be synthetically reproduced, they can only be used for
5.1.1 Ifpossible,theopticalconfigurationusedformeasure- performancetestingforlimitedtimeperiods.Iftestsamplesare
mentsoftestandchecksamplesshouldbeidenticaltothatused usedforthispurpose,collectionofhistoricaldataonanewtest
for normal operations. If identical optical configurations are sample should be initiated before previous test samples are
E1866 − 97 (2007)
depleted.Itisrecommendedthatnewtestsamplesbeanalyzed Typically, the intensity at five points centered on the test
sequentially with old test samples at least 15 times before they frequency are averaged.
are used to replace the old test sample. The 15 analyses must
7.2 Photometric Noise Tests—Photometric noise is mea-
be performed over a time period that does not exceed one
sured at the same frequencies (wavelengths) used for the
month in duration.
energy level tests. Preferably, photometric noise tests are
6.4 Optical Filters—An optical reference filter is an optical
conducted on a 100% line spectrum.Alternatively, photomet-
filter or other optical device located in the spectrophotometer
ricnoisetestsmaybeconductedonthespectrumofacheckor
or in a fiber optic sample probe which produces an absorption
test sample at regions where the spectrum is relatively flat and
spectrum which is known to be constant over time. This filter
the sample absorbance is minimal (<0.1).
may be automatically inserted into the optical path to allow
7.2.1 For single beam spectrophotometers where back-
instrument performance tests to be performed.
groundandsamplespectraaremeasuredseparatelyatdifferent
6.4.1 Optical filters are used principally with on-line pro-
times, a 100% line spectrum is obtained by ratioing two
cessspectrophotometersequippedwithfiberopticprobeswhen
successivebackgroundmeasurementstoobtainatransmittance
removal of the probe is inconvenient, precluding the use of
spectrum. If, during normal operation of the
check or test samples for routine instrument performance
spectrophotometer, backgrounds are collected with a reference
testing.
materialintheopticalpath,thenthissameconfigurationshould
6.4.2 If an optical filter is used routinely to check or correct
be used for performance testing. Photometric noise calcula-
thespectraldatacollectionorcomputation,thenthesamefilter
tions are preferably done directly on the transmittance spec-
ispreferablynotusedforinstrumentperformancetesting.Ifthe
trum. Alternatively, the transmittance spectrum may be con-
same filter is used, then the part of the filter spectrum used in
verted to an absorption spectrum by taking the negative log
the performance testing should preferably differ from that part
before the photometric noise calculations.
used to check or correct the instrument. For example, polysty-
7.2.2 For double beam spectrophotometers, a 100% line
rene filters are used to standardize (continuously check and
spectrum is measured when the two beams are both empty,
correct) the wavelength scale of some dispersive NIR spectro-
both contain empty matched cells, or both contain reference
photometers. For such systems, polystyrene filters are prefer-
samples in matched cells.
ably not to be employed for wavelength stability performance
7.2.3 Photometric noise is measured by fitting a line to the
testing. If polystyrene filters are used, then the peaks used for
spectrum over a short spectral region centered on the test
wavelengthstabilitytestingshouldbedifferentfromthoseused
frequency (wavelength). The region should contain at least 11
for standardizing the wavelength scale.
datapoints,preferablycontains101datapoints,andshouldnot
exceed 2% of the spectral range. The line is subtracted from
7. Univariate Measures of Spectrophotometer
thespectraldata,andtheRMSnoiseiscalculatedasthesquare
Performance
root of the mean square residual.
7.1 Energy Level Tests—Energy level tests are intended to
7.2.3.1 IfT isthetransmittanceatthefrequencyv,thenthe
i i
detect changes in the radiant power in the spectrophotometer
slope, m, and intercept, b, of a line through the n data points
beam. Decreases in energy levels may be associated with
centered at test frequency v are given by the following:
deterioration of the spectrophotometer source, with contami-
n iT 2 T i
nation or misalignment of optical surfaces in the light path, or
( i ( i(
m 5 (1)
with malfunctions of the detector.
n i 2 ~ i!
( (
7.1.1 For single beam spectrophotometers where back-
i T 2 i iT
( ( i ( ( i
groundandsamplespectraaremeasuredseparatelyatdifferent
b 5 (2)
n i 2 ~
...
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