OptLab-SPX Spectrum testing to min/max Values
For the quality control of optical samples and in pharmaceutical quality assurance, the comparison of a sample spectrum to reference data is common practice. Pass/reject decisions can be made if sample spectrum values do not
exceed and/or fall short of reference data. An example is the material control of Vaseline which is applied as a basis for quality test according to the European Pharmacopoeia (EP) and other national pharmacopoeias.
Vaselinum album after extraction according to EP must obey the following limits:
270–279 nm: max. 0.32 A
280–289 nm: max. 0.27 A
290–299 nm: max. 0.24 A
300–310 nm: max. 0.21 A
350–400 nm: max. 0.05 A
Similar tests must be performed
for example for antireflective coatings on glass substrates. An antireflective coating must not exhibit more than typically 0.5 % R at around 520 nm and must fulfill further limits at other wavelengths so that the coating does
not show color.
OptLab-SPX performs this type of testing using the min/max option. As the reference, a data table or spectra must be supplied. The data table consists of three columns: the first column contains the wavelengths, and the
second and third columns contain the minimum the maximum reference values respectively. All wavelength points in between the listed values are interpolated linearly. If a lower or upper limit is not of interest, a value outside
of the accessible ordinate range is used.
For the above described vaseline test the table would be of the following form (a spectrum with a 1 nm data interval is assumed):
Test Vaseline album according to EP
270 0.32 –1.0
279 0.32 –1.0
280 0.27 –1.0
289 0.27 –1.0
290 0.24 –1.0
299 0.24 –1.0
300 0.21 –1.0
310 0.21 –1.0
311 5.0 –1.0
349 5.0 –1.0
350 0.05 –1.0
400 0.05 –1.0
(The second column holds the minimum values. They are irrelevant for this test so that they are set to negative values.)
As an alternative to the data table, spectra may be used. The spectra have been recorded from reference samples or have been generated.
The list of OptLab-SPX calculation parameters can include any number of min/max tests with different reference data. OptLab can contain any number of such parameters in any combination. The result of a min/max test can be either
positive or negative. This is indicated as ‘within tolerance’ or ‘out of tolerance’ in the report. However this descriptive text can also be redefined separately by the OptLab user for each test.