Sample Preparation; Response Times; Interferences - Xylem WTW CN 500 DIN Instrucciones De Operación

Sample preparation

22
25 mg/l, as otherwise the electrode could be damaged irreversibly. If
you expect the concentration to be higher, dilute the sample according-
ly.
In the case of an erroneous calibration immediately after commissioning, pol-
ish the membrane surface (see M
Malfunctions can possibly occur due to the use of a magnetic stirrer. If the val-
ues are fluctuating heavily, we recommend to switch off the magnetic stirrer
during measurement.
Sample preparation
Add 1 % MZ/NH3/CN 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.
If you would like to have more detailed information concerning sample prep-
aration and measuring procedures, WTW provides a large number of appli-
cation reports for various applications.

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

 Complexes with Ni
 Strong reducing agents
 Interfering ions: 10 % error with the following concentration ratio
(concentration ratio = interfering ion / measured ion):
- -
Cl I
6
1x10 0.1
AINTENANCE
2+ 2+ 2+
, Cd , Cu
- 2-
Br S
3
5x10 must not be present
CN 500 / CN 800
).
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