Operation
XD 7500
50
ba77191e01 - 71310060
04/2018
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, e.g. the inherent coloring, is taken into account.
In practice, the reagent blank value is measured with the same amount of
deionized water instead of sample.
Factory-set and
individual reagent
blank values
With photometric concentration determination, the reagent blank value is a
constant. The method data for all pre-programmed methods (
Concentration
mode) includes a precisely 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).
Validity
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.
Single and multiple
determination
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.
User-defined meth-
ods
For user-defined methods, you can activate the reagent blank value function
as follows only:
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 recom-
mended 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 determination.
Entry type
Function type
Reagent
blank value
possible?
Enter a function
(with and without input of the
ordinate section)
Linear
Yes
Nonlinear
No
