ASTM E1866-97(2013)
(Guide)Standard Guide for Establishing Spectrophotometer Performance Tests
Standard Guide for Establishing Spectrophotometer Performance Tests
SIGNIFICANCE AND USE
4.1 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.
4.2 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 E275, E925, E932, E958, E1421, or E1683 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.
General Information
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: E1866 − 97 (Reapproved 2013)
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
E925Practice for Monitoring the Calibration of Ultraviolet-
1.1 This guide covers basic procedures that can be used to
Visible Spectrophotometers whose Spectral Bandwidth
develop spectrophotometer performance tests. The guide is
does not Exceed 2 nm
intended to be applicable to spectrophotometers operating in
E932PracticeforDescribingandMeasuringPerformanceof
the ultraviolet, visible, near-infrared and mid-infrared regions.
Dispersive Infrared Spectrometers
1.2 This guide is not intended as a replacement for specific
E958Practice for Measuring Practical Spectral Bandwidth
practicessuchasPracticesE275,E925,E932,E958,E1421,or
of Ultraviolet-Visible Spectrophotometers
E1683thatexistformeasuringperformanceofspecifictypesof
E1421Practice for Describing and Measuring Performance
spectrophotometers. Instead, this guide is intended to provide
of Fourier Transform Mid-Infrared (FT-MIR) Spectrom-
guidelines in how similar practices should be developed when
eters: Level Zero and Level One Tests
specific practices do not exist for a particular spectrophotom-
E1655 Practices for Infrared Multivariate Quantitative
eter type, or when specific practices are not applicable due to
Analysis
samplingorsafetyconcerns.Thisguidecanbeusedtodevelop
E1683Practice for Testing the Performance of Scanning
performance tests for on-line process spectrophotometers.
Raman Spectrometers
1.3 This guide describes univariate level zero and level one
3. Terminology
tests, and multivariate level A and level B tests which can be
3.1 Definitions—For terminology relating to molecular
implemented to measure spectrophotometer performance.
These tests are designed to be used as rapid, routine checks of spectroscopic methods, refer to Terminology E131.
3.2 Definitions of Terms Specific to This Standard:
spectrophotometer performance.They are designed to uncover
malfunctions or other changes in instrument operation, but do 3.2.1 action limit, n—the limiting value from an instrument
performance test, beyond which the spectrophotometer is
not specifically diagnose or quantitatively assess the malfunc-
tionorchange.Thetestsarenotintendedforthecomparisonof expected to produce potentially invalid results.
spectrophotometers of different manufacture.
3.2.2 check sample, n—a single pure compound, or a
1.4 This standard does not purport to address all of the known,reproduciblemixtureofcompoundswhosespectrumis
safety concerns, if any, associated with its use. It is the constant over time such that it can be used in a performance
responsibility of the user of this standard to establish appro- test.
priate safety and health practices and determine the applica-
3.2.3 level A test, n—a pass/fail spectrophotometer perfor-
bility of regulatory limitations prior to use.
mance test in which the spectrum of a check or test sample is
compared against historical spectra of the same sample via a
2. Referenced Documents
multivariate analysis.
2.1 ASTM Standards:
3.2.4 level B test, n—a pass/fail spectrophotometer perfor-
E131Terminology Relating to Molecular Spectroscopy
mance test in which the spectrum of a check or test sample is
E275PracticeforDescribingandMeasuringPerformanceof
analyzed using a multivariate model, and the results of the
analysisarecomparedtohistoricalresultsforprioranalysesof
the same sample.
This guide is under the jurisdiction of ASTM Committee E13 on Molecular
Spectroscopy and Separation Science and is the direct responsibility of Subcom- 3.2.5 level one (1) test, n—a simple series of measurements
mittee E13.03 on Infrared and Near Infrared Spectroscopy.
designed to provide quantitative data on various aspects of
Current edition approved Jan. 1, 2013. Published January 2013. Originally
spectrophotometer performance and information on which to
approved in 1997. Last previous edition approved in 2007 as E1866–97(2007).
base the diagnosis of problems.
DOI: 10.1520/E1866-97R13.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
3.2.6 level zero (0) test, n—a routine check of spectropho-
contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM
tometer performance, which can be done in a few minutes,
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. designed to visually detect significant changes in instrument
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
E1866 − 97 (2013)
performance and provide a database to determine instrument Spectraldatausedinperformancetestsshouldbedateandtime
performance over time. stamped, and the results of the tests should be stored in a
historical database.
3.2.7 optical reference filter, n—an optical filter or other
device which can be inserted into the optical path in the
6. Samples Used for Performance Testing
spectrophotometer or probe producing an absorption spectrum
6.1 Thesampleusedforperformancetestingischosentobe
which is known to be constant over time such that it can be
compatible with the spectrophotometer configuration, and to
used in place of a check or test sample in a performance test.
providespectralfeatureswhichareadequateforthetestsbeing
3.2.8 test sample, n—a process or product sample, or a
performed.
mixture of process or product samples which has a constant
6.1.1 The sample used for performance testing should
spectrum for a finite time period and which can be used in a
generallybeinthesamephysicalstate(gas,liquid,orsolid)as
performance test. Test samples and their spectra are generally
the samples to be analyzed during normal operation of the
not reproducible in the long term.
spectrophotometer.
4. Significance and Use 6.1.2 The sample used for performance testing should be
physically and chemically compatible with the samples ana-
4.1 IfASTM Committee E13 has not specified an appropri-
lyzed during normal operation.
ate test procedure for a specific type of spectrophotometer, or
6.1.3 The sample used for performance is chosen such that
if the sample specified by a Committee E13 procedure is
its spectrum is similar to the spectra which will be collected
incompatible with the intended spectrophotometer operation,
during normal operation.
then this guide can be used to develop practical performance
6.1.4 The sample used for performance testing should have
tests.
severalsignificantabsorbances(0.3
4.1.1 For spectrophotometers which are equipped with per-
thespectralrangeusedfornormaloperationofthespectropho-
manent or semi-permanent sampling accessories, the test
tometer.
sample specified in a Committee E13 practice may not be
6.1.5 In order to adequately determine the photometric
compatible with the spectrophotometer configuration. For
linearityoftheinstrument,thepeakabsorbanceforatleastone
example, for FT-MIR instruments equipped with transmittance
absorption band of the sample should be similar to and
or IRS flow cells, tests based on polystyrene films are imprac-
preferablyslightlygreaterthanthelargestabsorbanceexpected
tical. In such cases, these guidelines suggest means by which
for samples measured during normal operation.
the recommended test procedures can be modified so as to be
6.2 Check Samples—Check samples are generally used for
performed on a compatible test material.
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
weighed at ambient temperature. It is recommended that
4.2 Tests developed using these guidelines are intended to
mixtures be independently verified for composition prior to
allow the user to compare the performance of a spectropho-
use.
tometeronanygivendaywithpriorperformance.Thetestsare
6.2.2 While mixtures can be used as check samples, their
intended to uncover malfunctions or other changes in instru-
spectra may be adversely affected by temperature sensitive
ment operation, but they are not designed to diagnose or
interactions that may manifest themselves by wavelength
quantitatively assess the malfunction or change. The tests are
(frequency) and absorbance changes.
not intended for the comparison of spectrophotometers of
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
not possible, the user should recognize that the performance depleted.Itisrecommendedthatnewtestsamplesbeanalyzed
tests may not measure the performance of the entire instru- sequentially with old test samples at least 15 times before they
ment. are used to replace the old test sample. The 15 analyses must
5.1.2 Data collection and computation conditions should be performed over a time period that does not exceed one
generally be identical to those used in normal operation. month in duration.
E1866 − 97 (2013)
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
( i ( i(
nation or misalignment of optical surfaces in the light path, or
m 5 (1)
n i 2 ~ i!
with malfunctions of the detector.
( (
7.1.1 For single beam spectrophotometers where back-
i T 2 i iT
( ( i ( ( i
b 5 (2)
groundandsamplespectraaremeasuredseparatelyatdifferent 2
n i 2 ~ i!
( (
times, energy level tests are generally conducted on a back-
ground spectrum. For double beam spectrophotometers where
The photometric noise is calculated as follows:
the ratio of background and sample beam intensities is mea-
T 2 mi1b
sureddirectly,energylevelscanbemeasuredifitispossibleto ~ ~ !!
( i
Noise 5Π(3)
RMS
n 22
block the sample beam.
7.1.2 Ene
...
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