This Information Applies To: Agilent GTA 120, Agilent 240Z AA Spectrometer, Agilent 280Z AA Spectrometer, Agilent 240FS/GTA120/PSD120/UltrAA System
It is important to align the sample probe correctly with a PSD 120, so that the sample is injected properly into the graphite tube.
Steps to Follow:
- Adjusting the probe
The probe (i.e, the end of the capillary protruding from the base of the probe holder) should be adjusted so that:
a. The probe is correctly located in the center of the vials when it collects the solution.
b. The probe is correctly configured during rinsing.
c. The probe enters and exits the graphite tube without touching the sides of the injection hole.
d. The probe is set to the correct depth in the tube.
- To correctly position the probe:
1. Make sure that the GTA workhead is properly aligned with the optical path and that your PSD is properly installed.
2. Place an empty vial on the dispenser carousel in position 1.
3. Create a method worksheet. See the online Help.
4. Go to the "Analysis" page.
5. Select "Furnace Facilities" in the "Instrument" menu.
6. Turn on the camera (if installed).
7. Click "Align". The autosampler will position the capillary in position 1 in a completely down position. See Figure 1:
Figure 1. Graphite Furnace AA Sample Probe Alignment
8. Verify that the probe is correctly aligned to the sample vial. The probe should almost reach the bottom of the vial, but not actually touch it, as shown in Figure 2. If the end of the probe is too far from the bottom of the vial, or if it touches the bottom of the vial:
a.- Loosen the probe guide screw and adjust the length of the capillary as necessary.
b.- If necessary, loosen the screw on the probe holder and adjust the angle of the probe until it is aligned vertically in the vial.
Figure 2. Probe alignment in vial
9. Once the correct length of the probe in the vial has been established, click "OK" in the confirmation window, so the probe will move to the furnace head. Place a finger under the probe arm as the capillary begins to descend to the oven and gently lower the hand arm.
10. Release the locking screw located below the PSD. Use the adjustment buttons to the side and front of the PSD to adjust the sample position. When the probe is lowered, the injection hole of the graphite tube enters the sample without hitting the sides.
11. With the capillary properly centered, secure the autosampler using the locking screw.
12. Lower the capillary into the graphite furnace as shown in Figure 3 below. With the capillary down in the furnace, use the depth adjustment screw to fix the bottom tip of the probe to be about 1 mm above the bottom of the graphite tube or platform. Tighten the locking screw.
Figure 3. Lowering the Capillary into the Graphite Furnace
For more information, see the following video: Troubleshooting and Maintenance of Atomic Absorption Systems: Part 3- Graphite Furnace AAS