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photoLab
6100 VIS
Factory and user-
defined reagent
blank values
Validity
Single and multiple
determination
ba75847d06
06/2013
4.5.9 Reagent blank value
The evaluation of the photometric measurement always refers to the compar-
ison value of a test sample without the substance to be determined (reagent
blank value). Thus the influence of the basic absorbance of the reagents on
photometric measurement is compensated for.
In practice, the reagent blank value is measured with the same amount of de-
ionized water instead of sample.
With photometric concentration determination, the reagent blank value is a
constant. The method data for all measurements with WTW test sets (Con-
centration mode) include an exactly determined reagent blank value. This
value is overwritten if you measure the reagent blank value yourself (setting,
User-defined blank value, see section 4.5.6).
Note
You can increase accuracy if you determine the reagent blank value with a
test of a new lot and use the reagent blank value for all further measurements
with this lot. This is especially recommended for measurements in the vicinity
of the lower limit of the measuring range. To be able to attribute the reagent
blank value in the measured value documentation later, you can enter the lot
number of the reagent package (Lot number) during the blank value determi-
nation.
The factory blank values always remain stored in the meter and can be acti-
vated at any time. The reagent blank values you measured yourself also
remain stored in the meter until they are overwritten by a new blank value
measurement.
The reagent blank value can be determined with single or multiple determi-
nation. With multiple determination, the reagent blank value is calculated as
the median from the individual measured values.
Operation
57
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