40 Agilent Cary 8454 UV-Visible Spectroscopy System Installation Guide
3 Good Measurement Practices
General Considerations
Optical Specifications of Cells
The accuracy of the readings of a diode array instrument is very sensitive
to spatial shifts of the analysis light beam. Cells having non parallel
opposite faces, or so called wedge shaped cells, lead to a spatial shift of
the light beam (see Figure 6). Therefore, the opposite cell walls
illuminated by the analysis light beam have to be parallel. The degree of
parallelism is measured in terms of the angle between the two opposite
cell walls. We recommend that you use 10 mm path length cells with an
angle which is below 0.1 degrees of an arc.
Figure 6 Shift of the instrument light beam due to non parallel cell walls
Light Beam in
Light Beam out
Light Beam in
Parallel
Cell Walls
Non-parallel
Cell Walls
Light Beam out
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