Troubleshooting and Maintenance of AA Systems: Part 2B- Flame Optimization

Agilent Support Insights

This Information Applies To: All Agilent Flame AA Systems- 55B, 240FS, 280FS 

Issue:

After cleaning and re-installing the flame atomic absorption system components, it is important to optimize the burner position, nebulizer uptake rate, flame conditions, glass impact bead, and mixing paddles. Proper optimization ensures that the atomic absorption system will yield accurate and precise results throughout its lifetime.

Steps to follow:

1. Optimize the burner position vertically, horizontally, and rotationally using the burner alignment card, as shown in Figure 1.

                              Figure 1. Optimization with the burner alignment card.

2. Attach the plastic capillary tubing to the nebulizer. Wind the nebulizer locking thimble and locking ring clockwise, as far as they go.

3. To determine the nebulizer uptake rate, ignite the flame, and aspirate distilled water from a small graduated cylinder over a one minute time period. Adjust the locking thimble until the uptake rate is between 5-6 mL per minute (ml/min), as shown in Figure 2. Then tighten the locking ring (behind the locking thimble).

                                        Figure 2. Optimizing the nebulizer uptake rate.

4. Go to the worksheet window and click the optimize button. Select or develop a Cu method to use for optimization. When the hollow cathode lamp has completed its peaking procedure, click "Optimize Signal" and then do an "Instrument Zero" while still aspirating distilled water, as shown in Figure 3.

                                          Figure 3. Optimize signal and instrument zero.

5. Aspirate a 5 ppm Cu solution. Optimize the burner position vertically, horizontally, and rotationally, as shown in Figure 4, and the flame conditions to yield the highest signal. Then adjust the glass impact bead position to achieve the maximum signal and minimum noise. Remember to turn the adjustment screw counterclockwise. Close the optimization window by clicking "OK".

                                           Figure 4. Optimize the burner position.

6. For most flame AA applications, the mixing paddles should be fitted in the spray chamber, and the glass impact bead should be adjusted for best sensitivity. If you have more difficult samples to run, such as high % total dissolved solids (TDS), ensure that the mixing paddles are in place inside the spray chamber.  Adjust the impact bead at least half a turn clockwise from the optimum sensitivity position. This will give better performance with difficult sample types.

Keywords: flame atomic absorption, 55B, 240FS, 280FS, nebulizer uptake rate, spray chamber, mixing paddles, impact bead,