Hach-Lange POLYMETRON 9240 Operator Manual - Manual (Page 34)

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Analyzer Overview
3.8 Manual calibration cycle
The following section gives an overview of the manual calibration process. For details on setting
up and running this processes, refer to the section entitled
Calibration on page 93 . As the 9240
is a multi channel analyzer, the user must define which channel will be used for calibration (see
Automatic calibration setup on page 99 ). If the analyzer is set up as a single channel unit, then
calibration will always be made on channel 1 by default.
This process calculates the slope and offset of the ISE sodium electrode and the reference
electrode. It is based on the measurement of potential and temperature of two different samples
of known sodium concentration.
The concentration values of the two calibration solutions must be entered into the analyzer prior
to calibration (see
Two point calibration on page 98 ). The lower concentration should be greater
than 50 ppb and the relationship between low and high concentration should be 10 or more. The
recommended low value is 100 ppb and the high value is 1,000 ppb.
The cycle is as follows:
1. Phase 1: The electrode is reactivated. This consists of injecting Sodium Nitrate into the
solution to maintain a high level of sodium measurement for a minimum of 5 minutes.
2. Phase 2: The measurement cell is rinsed.
3. Phase 3: The overflow vessel is rinsed and refilled with fresh sample.
Figure 11 Manual calibration cycle