Endress+Hauser Analytik Jena multi EA 5000 - Page 65

multi EA 5000 Chlorine analysis with the Cl module
65
¡ The finished electrolyte solution (solutionC) can be kept for approx. 30days if kept
in a well-sealed glass container at 20to 25°C.
Performing the end point rou-
tine
An end point routine is necessary after every electrolyte change. The end point routine is
used to adjust the electrolyte to the optimal operating range of the measuring cell. The
operating point of the measuring cell is: 1500 to 5000 Counts
.
} Start the end point routine via the
System
|
End point routine
menu item.
} Remove the olive from the lid of the measuring cell. Dose the HCl solution directly
into the measuring cell when instructed to by the software.
"sensitive"
measuring cell: 200 µl of 0.01 N HCl
"high concentration"
measuring cell: 200 µl of 0.1 N HCl
} Directly after dosing, activate the end point routine by clicking on
[OK]
.
} The
End point routine
status is displayed in the
Status analyzer
window during this
routine. After the end point routine, the
Stand-by titration
and the current indicator
value is displayed.
ü The system is ready for measurements.
The determined operation point of the combined electrode is displayed in the
System
|
Component test
menu item in the
Chlorine
tab.
Protecting the combined elec-
trode
Observe the following to protect the combined electrode against unnecessary wear:
¡ Always add fresh electrolyte to the measuring cell before the end point routine.
¡ Do not carry out the end point routine several times in a row.
8.3.1.2 The "high sensitive" measuring cell
Measurements with the "high sensitive" measuring cell require an electrolyte solution. In
addition to that, an internal electrolyte for the sensor electrode must be prepared which
is also used for storing the electrode. Use the same water the both solutions.
Preparation of the electrolyte
solution
WARNING
Risk of chemical burns
100% acetic acid (glacial acetic acid) can cause severe chemical burns. Gases may de-
velop during shaking.
¡ Wear protective clothing when preparing the electrolyte solution. Work under an ex-
tractor.
¡ Observe all instructions and specifications in the safety data sheet.
ð Reagents required: 800 ml acetic acid 100% (glacial acetic acid), 2.7g sodium ac-
etate p.a. (CH
3
COONa), anhydrous
} Dilute 2.7g of sodium acetate in 200ml of ultrapure water in a 1-liter volumetric
flask.
} Carefully add 800ml of glacial acetic acid. Keep moving the flask while pouring the
acid. Carefully shake the mixture.
NOTICE!Do not exceed the specified amounts of water and glacial acetic acid. Do
not fill the flask up to the 1-liter mark (volume contraction).