ASTM E579-84(1998)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
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Designation:E579–84(Reapproved1998)
Standard Test Method for
Limit of Detection of Fluorescence of Quinine Sulfate
This standard is issued under the fixed designation E 579; 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 (ε) indicates an editorial change since the last revision or reapproval.
1. Scope E 578 TestMethodforLinearityofFluorescenceMeasuring
Systems
1.1 This test method employs the signal-to-noise ratio
theory to determine the sensitivity of a fluorescence measuring
3. Summary of Test Method
system in testing for the limit of detection (LOD) of quinine
3.1 To measure the concentration corresponding to the limit
sulfate. The results obtained with quinine sulfate are suitable
of detection, the amplification is increased until the noise
for specifying instrument performance on samples having
observed with pure solvent in the sample cell is large enough
excitation and fluorescence bands wider than 10 nm.
to measure on the amplifier readout. The test solution is then
1.1.1 This test method is not intended to be used as (1)a
diluted until readings on both the test solution and pure solvent
rigorous test of performance of instrumentation, or (2), to
can be read at the same amplification setting. The concentra-
intercompare the quantitative performance of instruments of
tion corresponding to the limit of detection is that at which the
different design.
noise, multiplied by three, is equal to the signal. The concen-
1.2 This test method has been applied to fluorescence-
tration of the sample corresponding to the limit of detection
measuring systems utilizing continuous and low-energy exci-
arrived at by this technique is indicative of the inherent noise
tation sources (for example, an excitation source of 150-W
2 in the instrument.
electrical input or less). There is no assurance that extremely
3.2 This test for limit of detection requires an instrument to
intense illumination will not cause photodecomposition of the
beingoodcondition:stable,freeofextraneousnoise,electrical
compound suggested in this test method. For this reason, it is
pickup, and internal stray light. The sample space must be
recommended that this test method not be indiscriminately
covered to exclude room light. The instrument should be
employed with high intensity light sources. This test method is
operatedaccordingtothemanufacturer’srecommendations,or,
not intended to determine minimum detectable amounts of
if they are modified, the modifications must be applied consis-
other materials. If this test method is extended to employ other
tently to the test for limit of detection and to the analysis for
chemical substances, the user should be aware of the possibil-
which the test is a requirement, so that levels of performance
ity that these other substances may undergo decomposition or
are comparable for both.All modifications must be included in
adsorption onto containers.
the report.
1.3 The practical lower limit of this test method is 1 ng of
quinine sulfate per mL (one part per billion; 1 ppb).
NOTE 1—To obtain the lowest reading (the best instrumental response)
1.4 This standard does not purport to address all of the for the limit of detection of fluorescent material, a number of precautions
must be taken. The condition and position of the sample cell are most
safety problems, if any, associated with its use. It is the
important. The cell must be free of scratches and marks that scatter light
responsibility of the user of this standard to establish appro-
into the emission monochromator. Only spectral grade chemicals and
priate safety and health practices and determine the applica-
solvents (including water) should be used. Dilute solutions should be
bility of regulatory limitations prior to use.
made, just before use, from concentrated stock solutions.All samples used
must be maintained at the same temperature to obviate effects due to
2. Referenced Documents
temperature coefficients.
2.1 ASTM Standards:
4. Significance and Use
4.1 When determining the limiting detectable concentration
This test method is under the jurisdiction of ASTM Committee E-13 on
of a fluorescent substance, it is usually necessary to increase
Molecular Spectroscopy and is the direct responsibility of Subcommittee E13.06 on
the amplification of a photoelectric instrument to a point where
Molecular Luminescence.
Current edition approved March 30, 1984. Published May 1984. Originally noise (that is, random fluctuations of the system) becomes
published as E 579 – 76. Last previous edition E 579 – 76.
Except laser-excited
Lukasiewicz, R. J., and Fitzgerald, J. M., Analytical Chemistry, ANCHA, Vol
45, 1973, p. 511. Annual Book of ASTM Standards, Vol 03.06.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
E579
apparent.Thisnoisewillbesuperimposeduponthesignalfrom 6.3 Set the time constant, if adjustable, to the value nearest
the sample; it arises from several sources, such as instability in to 1 s, so that it is equivalent to a 98 % response time of 4 s.
the zero point, tube noise, and statistical variations in the
6.4 Put the pure solvent, in this case 0.1 N H SO , in the
2 4
photoelectric current.
sample cell and increase the amplification of the fluorescence-
4.2 In molecular fluorescence spectroscopy, the limit of
measuring system to maximum or until the peak-to-peak noise
detection for the sample will be determined by the limiting
is approximately 5 % of full scale on the readout device. Set
signal-to-noise ratio, S/N, where the signal, S, is the difference
the zero adjustment to bring the reading of the solvent to
between readings obtained with the sample and blank solu-
slightly above zero on the scale. Measure the signal from at
tions, and N is the total root-mean-square (rms) noise due to all
least ten independent readings, rem
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