Operation
inoLab pH/ION 735
48
4.5.7
Standard subtraction (
Std. sub.
)
In the "Standard Subtraction" procedure, a known amount of standard
solution is added to the sample (as complexing agent or precipitating
agent) and, thus, the ion concentration lowered.
The ion concentration in the sample is calculated from the change in
potential.
Measuring
1
Select the measuring method (see section 4.5.5).
2
Prepare two standard calibration solutions.
3
Perform a two-point calibration according to the user guidance.
4
As soon as a stable value is achieved for the second standard
calibration solution, the slope (mV) and evaluation (+ ... +++) of
the electrode after calibration is displayed.
i
Slope =
33.6 mV
i
Sensor
+++
Accept
ISE <CAL>
5
Start the measurement with
g
.
An entry window appears.
6
Thoroughly rinse the electrode with deionized water.
7
Immerse the electrode in the sample.
8
Using
82
and
g
, select the values for the volume of the
sample (
Sample volume
) and the volume of the ISA/TISAB so-
lution (
ISA/TISAB vol.
).
9
Select
Continue
with
82
and start the measurement with
g
.
When the measurement is finished an info window appears.
i
Immerse sensor in sample
Sample volume
100.0 ml
ISA/TISAB vol.
1.0 ml
Continue
Standard subtraction
