Xylem wtw NO 800 DIN, Руководство по эксплуатации

Страница: 19 / 46

NO 800 Sample preparation
ba15362d04 12/2021
19
Sample preparation
Add 50 % TISAB/NO3 solution.
This sample conditioning solution creates optimum conditions for measuring.
It provides a constant ionic strength and similar diffusion potentials at the
reference electrode in standard solution and test sample.
Response times
The response time depends on the concentration range. It is

several seconds at high concentrations,

several minutes near the detection limit.
The measured value is stable if the value does not change by more than
0.1 mV within 30 seconds.
Interferences
Interfering ions: 10 % error with the following concentration ratio
(concentration ratio = interfering ion / measured ion):
The conditioning time depends on the previous history of
the ion sensitive electrode. To achieve a good responding
behavior, the concentration of the standard solution should
be similar to the concentration expected of the test sample.
During commissioning and after long periods of storage:
condition the electrode overnight.
Connect the electrode(s) to the meter and switch to the
measured value display (see operating manual of the
meter). The ion sensitive electrode is sufficiently condi-
tioned when the measured value no longer changes consid-
erably under otherwise constant conditions (temperature,
composition of the solution).
2 Remove any air bubbles in the bridge electrolyte by slightly knocking
against the shaft.
3 Calibrate according to the operating manual of the meter and the
analysis specification.
If you would like to have more detailed information concerning
sample preparation and measuring procedures, WTW provides
a large number of application reports for various applications.