Metrohm NIRS XDS Transmission OptiProbe Analyzer - Manual (Page 48)

46 ▪▪▪▪▪▪▪
1. The standard must be a valid XC-1300, labeled WST3Wxxx on top. (The color of the front
optical glass should appear reddish or pinkish. (Not greenish.)
2. All components should be clean. The standard should not have any dirt, fingerprints, or other
optical interferences.
3. This test must be performed in the calibration fixture to assure proper alignment.
4. The operator should follow the instructions in Vision about when to insert the standard, etc. If
this is not performed in the correct order, the test will not pass.
Information about the wavelength standard:
The Metrohm XC-1300 Transmission Calibration Standard (dark blue spectrum) used is directly
traceable to NIST SRM-2035 (magenta spectrum) through direct comparison on the Metrohm master
transmission instrument. This material has very sharp bands, which are found to be stable and
repeatable. The Metrohm NIRSystems XC-1300 Transmission Calibration Standard has peaks in more
locations than the SRM-2035 standard, and covers the full wavelength range more thoroughly.
These additional bands (peaks) are used to set the wavelength scale of the instrument to aid in
instrument matching. This is one important step in calibration transfer.
In Wavelength Certification, the NIST-stated uncertainty of 1.0nm is applied. Tighter tolerances are
not appropriate, unless NIST revises the stated uncertainty of SRM-2035 at some point in the future.
In Instrument Calibration, FOSS has assigned tighter tolerances to certain well-defined, stable peaks,
based upon extensive testing with this type of instrument. The instrument is calibrated to these
tighter peaks as a way to enhance model transfer between like instruments. “Absolute” transfer may
be difficult due to fiber position and other optical factors.
It is important to perform Instrument Calibration and Wavelength Certification at consistent
temperatures to assure repeatable wavelength response. All optical components, including standards,
are subject to drift with temperature. We advise performing these tests at a consistent temperature