 |
 |
|
|
|
|
Because of its robustness and chemical
inertness FotoSense is especially attractive for use with process
analysers and ensures trouble free unattended operation. |
|
|
Determination of water hardness
A very common application of the FotoSense is in the
determination of the calcium and total hardness of city water. The
methodology is very straightforward. The sample is made alkaline with an
ammonium chloride / ammonia buffer and a small amount of eriochrome black T
(EBT) solution added (*). A FotoSense 630 (red) is used to follow the
titration with EDTA. At the end-point there is a sharp change from red to
blue and a very distinct step change of the sensor output.
The graphic shows typical titration curves using two different amounts of
EBT indicator. This photometric titration is a very stable and unproblematic
in contrast to a potentiometric measurement with for example a calcium ion
selective electrode which drifts and looses sensitivity in a matter of a few
months.
|
|
|
