Metrohm Vision – Diagnostics - Manual (Page 34)

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Low-Flux Test
Low-Flux Test is included for users who must run this test in support of regulatory requirements such
as the United States Pharmacopoeia (USP) General Information Chapter on Near-Infrared
Spectroscopy, <1119>. It can be run either on its own or in a truncated fashion as part of the USP
tests. The reported values and specification limits are different between the two types of Low-Flux
Test, with the USP test tolerances being much broader.
Low-Flux Test uses a nominal 10% reflectance standard in the sample position. (Reflectance
Standards contain a 10% reflectance standard (R101xxxx), which may be used for this test.) A noise
test is run using this standard. Because the reflectivity is less than the instrument standard, the test is
considered a good method for testing instrument noise in the range of reflectivity of many common
sample absorptions. This test verifies that the instrument is working properly at higher levels of
absorbance.
The Low-Flux Test is performed in reflectance and may use the 10% Certified Reflectance Standard
used in IPV Setup and the Photometric Test. If the user substitutes another 10% sample, it should be
of fairly flat spectral character, and be as close to 10% reflectance as possible. If the sample chosen is
too dark (less than 10% reflectance) the test will be unnecessarily severe, and the instrument may fail
the test. The acceptance specifications loaded into Vision are for the Certified 10% Reflectance
Standards and the internal screen that can be used on the XDS instruments.
The XDS instrument has an internal 10% neutral density (transmittance) screen, triggered by
software, which can be used in place of an external 10% reflectance standard. This screen gives
equivalent results during the Low-Flux Test, and minimizes the possibility of operator error in placing
the standard.
To initiate the Low-Flux Test, follow this
sequence:
From the Diagnostics menu bar, select Low-Flux
Test.