Metrohm 789 Robotic Sample Processor XL - Manual (Page 142)

6.2 Standard methods
134 Metrohm Sample Processor, Annex
6.2.4 pH_cal
This is a universal method for automated pH measurements directly in
the sample beaker. The electrode calibration is included in the start se-
quence.
Required instruments and cables:
• Metrohm pH Meter (model 691 or 780/781) with 6.2148.010 Remote
box
• Metrohm 802 Propeller Stirrer or 741 Magnetic Stirrer
• 6.2141.020 Remote cable
The method can be used with or without a 786 Swing Head on the
Sample Processor. In the rack definition the special beaker positions 1
to 3 must be reserved.
Special features:
The two buffer solutions for the electrode calibration must be in special
beaker positions 1 and 2.
After each measurement the electrode is rinsed in a rinsing beaker at
special beaker position 3. Internal or external pump required for rinsing.
If a 780/781 pH Meter is used, two additional command lines must be
inserted in the start sequence of the method. This is to cancel the dis-
play of the calibration results:
17 SCN:Rm : end1
18 WAIT: pause 1 s
19 CTL:Rm: START device1
20 MOVE 1 : spec.3
789 Sample Proc. XL 11122 5.789.0011
parameters
method pH cal
number of samples: rack
>start sequence
1 CTL:Rm: INIT
2 MOVE 1 : spec.3
3 LIFT: 1 : work mm
4 PUMP 1.* : 4 s
5 MOVE 1 : spec.1
6 LIFT: 1 : work mm
7 STIR: T1 : 10 s
8 CTL:Rm: METER cal pH
9 SCN:Rm : End1
10 MOVE 1 : spec.3
11 LIFT: 1 : work mm
12 PUMP 1.* : 4 s
13 MOVE 1 : spec.2
14 LIFT: 1 : work mm
15 STIR: T1 : 10 s
16 CTL:Rm: METER enter
17 SCN:Rm : End1
18 MOVE 1 : spec.3
19 LIFT: 1 : work mm
20 PUMP 1.* : 4 s
>sample sequence
1 SHIFTRATE:+ 20
- Report header with device ID and program version
- Method name
- No. of samples (here whole sample rack)
- Initialize Remote interface
- Move to rinse beaker
- Lower electrode
- Rinse electrode and aspirate beaker
- Move to buffer 1
- Immerse electrode
- Stir for 10 seconds
- Start calibration with 1st buffer
- Wait for calibration
- Move to rinse beaker
- Lower electrode
- Rinse electrode and aspirate beaker
- Move to 2nd buffer
- Immerse electrode
- Stir for 10 seconds
- Start calibration with 2nd buffer
- Wait for calibration
- Move to rinse beaker
- Lower electrode
- Rinse electrode and aspirate beaker
- Rack rotation direction counterclockwise