Thermo orion 410Aplus, Instruction Manual

Page: 42 / 129

Benchtop pH/ISE Meter Instruction Manual
Special Features 41
Set-up
1. Refer to the appropriate electrode instruction manual for preparation
of sensing and reference electrode(s), required solutions (ionic strength
adjusters, standards...), and any special requirements.
2. Securely connect electrode(s) to either input 1 or 2. The number of
the input in use will appear directly before the electrode ID. For
example, 1-Cl
-
. Select the appropriate input by pressing
2nd then channel.
3. Identify the electrode in use by pressing 2nd then electrode id and set
up other instrument operating parameters.
4. If a single incremental technique is to be performed, determine the
electrode slope from a previous calibration or as directed in the
electrode instruction manual.
Single Incremental Techniques
Single incremental techniques are useful for occasional samples or samples
with complex matrices. Another advantage of the single incremental
techniques is that the electrodes are not moved from solution to solution
during calibration and measurement. This eliminates errors due to solution
carryover and static charge disturbance of the electrode membrane.
It is especially important to be sure that any complexing agent is present in
great excess or not at all. The ratio of free ion to complexed ion must
remain constant over the addition. An indication that a complexing agent is
present, but not in great enough quantity to maintain a constant
free/complexed ion ratio, is an abnormally high or low slope. If this is
a suspected problem, an excess of complexing or decomplexing agent
may be added to the original solution in the beaker prior to the
incremental addition.