Xylem photoLab 6600 UV-VIS - Manual (Page 60)

Operation photoLab
®
6600 UV-VIS
60 ba75848e01 08/2009
Determining the
calibration function
You have the following options to create a method:
z Measure and store:
Carry out a series of measurements with the following sample solutions
while at the same the photometer takes over the values:
– Blank sample to determine the reagent blank value
(with deionized water instead of sample, see section 4.5.9)
– at least one, up to ten standard solutions in different concentrations.
The photometer stores the nominal value/absorbance value pairs of the
individual measurements and determines the resultant characteristics of
the calibration. When doing so, you can select the following line types:
Polygon line, Straight line or Parabola.
z Enter as value pairs:
Entry of the value pairs, Nominal value (concentration) / Measured
absorbance of an already available test series with the following sample
solutions:
– Blank sample to determine the reagent blank value
(with deionized water instead of sample, see section 4.5.9)
– at least one, up to ten standard solutions in different concentrations.
Based on the entered value pairs, the photometer determines the
characteristics for the calibration. When doing so, you can select the
following line types: Polygon line, Straight line or Parabola.
z Enter a function:
Entry of a function to calculate the concentration from the absorbance
(reverse calibration function). You can enter on the photometer the
coefficients of a polynomial equation of the following type:
c = a0 + a1·A + a2·A
2
+ a3·A
3
+ a4·A
4
+ a5·A
5
Note
Entering the formula is especially simple if you measure with a commercial
test set for which the manufacturer has given the value for the coefficient a1.
It is often called the "Factor" and corresponds to the reciprocal value of the
slope of the straight line of the calibration function.
If a linear function (straight line) should be entered, it is necessary to enter
the coefficients a0 and a1 to receive correct measured values.
with:
c Measurement result, e.g. concentration
a0 to a5 Coefficients (input range 0.000 to 1000,000)
A Absorbance