Eppendorf BioSpectrometer kinetic - Manual (Page 26)

Operation
Eppendorf BioSpectrometer
® kinetic
English (EN)
26
5.3.3 Important measurement instructions
5.3.4 Notes on working with cuvette temperature control
Temperature control is regulated using a measurement on the cuvette holder. The temperature in the
measuring solution may deviate from the temperature on the cuvette holder.
The extent of the deviation is dependent on the measuring volume, cuvette material, cuvette shape and
ambient temperature. The temperature control speed is also dependent on these factors. The temperature
control of plastic cuvettes is slower compared to glass cuvettes. The surface of the cuvette in direct contact
with the wall of the cuvette holder should be as large as possible to ensure quick temperature control.
Therefore, the temperature control of plastic semi-micro cuvettes as well as, for example, the UVette is only
performed slowly.
Check for each measurement:
• For plastic cuvettes: How many consecutive measurements can be reliably carried out in
the cuvette?
• Measure the cuvette blank value before the sample or standard measurements in order to
compensate the cuvette blank value in addition to the reagent blank.
• Blank results remain saved for one measuring series, but a new blank result measurement
can be performed at any time, even between sample measurements.
• The displayed absorbance values always correspond to the directly measured values. The
dilution or cuvette factor as well as background absorbances only will be incorporated for
the following result calculation (see Absorbance values on p. 89).
• The measuring result is typically displayed 2 to 3 seconds after a measurement has been
started. If a small amount of light reaches the receiver, the measuring time automatically
can be extended to 9 seconds in order to increase the precision of the measurement. For
kinetic measurements, the automatic extension of the measuring time is not applied in
order to prevent any conflicts with the preprogrammed interval time for the measuring
point recording.
• Observe that the measured absorbance values do not exceed the upper limit of the
photometric measuring range. In this case, reject the measuring result. The upper limit of
the photometric measuring range does not only depend on the wavelength (see
Photometric properties on p. 86) but also on the cuvette blank. Ultra-micro cuvettes with a
small diaphragm, such as
TrayCell (Hellma), may have a cuvette blank of approx. A = 1.
The available photometric measuring range is reduced by this amount. You can estimate
the cuvette blank by measuring the cuvette filled with demineralized water as a sample in
comparison with the empty cuvette shaft as a blank. The cuvette blank of the Eppendorf
μCuvette G1.0 is negligible (approximately A = 0).
• After the measurement, remove the measuring solution completely before filling in the
next measuring solution in order to minimize carry-over. If a carry-over from one sample to
the next sample can be expected due to a high concentration difference, rinse the cuvette
between the measurements.
• If the temperature between the lamp and the ambience differs, photometric drift may
occur. Therefore a device from a colder ambience first has to be adjusted to the ambient
temperature.
Avoid quick changes of temperature. Carry out a new blank measurement for a long series
of measurements or measurements over a long period of time.