thermo spectronic GENESYS 10, Operator'S Manual, Page: 22 / 77

specifications and ensure that you work
within the recommended range.
Test tubes vs. cuvettes
• Square cuvettes that are carefully matched
(see “Correcting for cell variability” below) yield
very precise results. Matched test tubes, when
properly handled, can show as little as 1-2%
deviation between readings.
• The pathlength of test tubes is not as well
defined as in square cuvettes. However,
constructing a standard curve eliminates the
need for great accuracy in knowing the
pathlength, provided that the same pathlength
cell is used for all blanks, standards and
samples.
Other guidelines
• Be sure to position cuvettes and test tubes so
that the clear sides face the light beam. This
means that one clear side should face the front
of the instrument and the other clear side
should face the back of the instrument.
Note: Test tubes should always be placed in the
instrument in exactly the same orientation
in the light beam. A fiducial mark on the
test tube helps you orient the test tubes
consistently and correctly.
• When using small aperture cells:
•
Always use masked cells.
• Use the same cell (or cuvette) for your
blank and your samples.
Correcting for cell variability
Due to variability in cell manufacture, each cell may
have slightly different absorbance and reflection
characteristics. Although it would be ideal to use
exactly the same cell for every reading, it is usually
inconvenient to clean cells between readings.
The GENESYS 10 UV
scanning model uses an
automated program to correct for cell variability ,
allowing you to use up to six unmatched cuvettes.
Nearly any cell can be used with a high degree of
accuracy if you have run the cell correction program
on those cells.
Z-dimensions
The figure below illustrates the position of the light
beam in the spectrophotometer.
The specifications for the sample compartment,
including the dimensions of the beam are:
•
Z-dimension
•
Square cuvettes/Test tubes 8.5mm
• Beam size 2mm (wide) x 7mm (high)
Setting Up the Instrument
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