Eppendorf BioPhotometer plus - Manual (Page 18)

5 Operation
18
BioPhotometer plus — Operating manual
5.3.3 Measure
1. Open the cuvette shaft by sliding the blue cover back.
blank 2. Fill the cuvette with blank solution and insert the filled cuvette into the cuvette shaft.
3. Press the blank key.
Standards
(optional)
4. Only for methods with standard evaluation: Measure the required standards consecutively if
you want to carry out a new calibration (see Methods with evaluation via standards on
page 21).
Samples 5. Fill the cuvette with sample solution and press the sample key.
Hint!
Check for each measurement:
• Is there enough measuring solution in the cuvette? The light path height of the BioPhotometer
plus is 8.5 mm. The height of the light beam in the cuvette is 1.5 mm.
• Is the measuring solution free from particles and bubbles?
• Is the measuring surface of the cuvette free from contamination due to dust or finger prints
and free from scratches?
• When inserting the cuvette press it all the way down against a slight resistance.
• Is the cuvette positioned correctly? The optical surface of the cuvette must point towards the
direction of the light path. The direction of the light path in the BioPhotometer plus is indicated
by an arrow on the blue cuvette shaft cover.
• For plastic cuvettes: How many consecutive measurements can be reliably carried out in the
cuvette?
• Carry out a blank measurement for each cuvette before any sample or standard
measurement to compensate for the cuvette blank in addition to the reagent blank value.
• Check whether the measured absorbance values exceed the upper limit of the photometric
measuring range. Discard the measuring result in this case. The upper limit of the
photometric measuring range not only depends on the wavelength (see Photometer on
page 41) but also on the cuvette blank. Ultramicro cuvettes with a small aperture such as
"TrayCell" (Hellma) or "LabelGuard" (Implen) may have a cuvette blank of up to A = 1. The
available photometric measuring range is reduced by this amount. You can estimate the
cuvette blank if you measure a water-filled cuvette as a sample against the empty cuvette
shaft as a blank.
• Remove the measuring solution completely after measurement before filling the next
measuring solution in order to minimise carry-over. If a carry-over between samples is
expected due to the high concentration differences then flush the cuvette between
measurements.
• With temperature differences between the lamp and the environment photometric drift may
occur. Therefore a device being brought in from a colder environment should first reach the
ambient temperature. Alternatively you can bring the lamp to the right temperature by carrying
out a few measurements. In long series of measurements or in measurements over a long
period of time carry out a new blank measurement.
• Top: method name and display of the sample type
(here: "BLANK")
• Center: result (for blank: 0.000 A)
Hint!
Blank results remain stored as long as the method remains open. However, we recommend to
check the blank at regular intervals of e.g. one hour. To do so carry out a measurement with the
blank solution as sample. If the measuring result differs significantly from 0 a new blank
measurement must be carried out.
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