Calibration; Calibration Strategies; Daily Factor - Endress+Hauser analytikjena multi N/C UVHS Operating Manual

multi N/C UVHS, multi N/C pharma UV
3.5

Calibration

3.5.1

Calibration strategies

3.5.2

Daily factor

Multiple point calibration with constant sample volume
In many applications, multiple point calibration with a constant dosage volume and mul-
tiple standard solutions at different concentrations is suitable.
The calibration range can encompass a wide range of concentrations and must be de-
fined in accordance with the expected sample concentrations. Multiple standard solu-
tions are measured with the selected method.
Multiple point calibration with constant concentration
Additionally, a multiple point calibration with variable dosage volumes and constant
concentration can be performed. This calibration strategy is particularly interesting and
the norm in the pharmaceutical industry for measurements at very low concentrations
(<1 mg/l).
Only create one standard solution for the calibration range. The analyzer then analyzes
different volumes of this standard solution. Do not go below the lowest standard solu-
tion volume of 1.6 ml when doing this.
Check the calibration via a second independently made standard solution to exclude er-
rors during standard solution creation.
Take the blank value of the preparation water into account for measurements in the
range of low concentration (<10 mg/l).
Single point calibration
For low TOC concentrations such as those in the pharmaceutical industry, single point
calibration is a very good solution. A big advantage is that the device blank value is low
and that the NDIR detector performs linear measurement across a wide range of con-
centrations.
Proceed as follows to minimize errors during manual standard solution creation:
Prepare 3 standard solutions at the same concentration.
¡
¡ Measure the standard solutions.
¡ Determine the calibration curve from the average value in the results.
Take the blank value of the preparation water into account during single point calibra-
tion.
Calibration with a standard solution can be checked and corrected via the daily factor.
The software multiplies all subsequent measurement results with this factor.
The daily factor F is calculated in accordance with the following formula:
F = c /c
target actual
Function and design
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