Horiba Scientific LAQUAact D-72G, Instruction Manual

Page: 38 / 94

pH measurement
18
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Performing calibration
Calibration is necessary to measure pH accurately.
We recommend performing calibration once a day, before the first measurement.
According to the following procedure, perform calibration accurately.
Note
・
Perform two-point calibration using pH 7 and pH 4 when you know that the sample is
acidic; pH 7 and pH 9 when you know that the sample is alkaline.
・
Perform three-point calibration using pH 4, pH 7, and pH 9 when the sample is unknown.
・ You can confirm the current calibration data in the data mode and delete the calibration
data in the setting mode. (Refer to “ Displaying the latest calibration and inspection data ”
(page 33), “ Deleting calibration data ” (page 35).)
• pH standard solution setting is NIST or USA
This section describes the procedure for two-point calibration of NIST, pH 4 and 7, as a
general calibration example.
1. Press the key to enter the calibration mode.
2. Wash the pH electrode with pure water (or
deionized water) and wipe it with filter paper or
tissue paper.
3. Open the internal solution filler port of the pH
electrode.
If calibration is performed with the port closed, the
internal solution does not flow and the
measurement value is not stabilized. Make sure to
keep the port open during calibration.
4. Perform the 1st point calibration. Immerse at
least 3 cm from the tip of the pH electrode in
the pH 7 standard solution.
In order to flow the internal solution into the
standard solution, immerse the liquid junction in
the standard solution surely.
key