This Information Applies To: All Agilent Flame AA Systems: e.g., 55B, 240FS, 280FS
It is important to maintain your flame atomic absorption system and clean when necessary, to keep your AA instrument in good working order. This practice will lead to the best results and will also reduce downtime. This document focuses on cleaning and maintaining the components of your Flame AA system including the burner, nebulizer, and spray chamber. It is based on the Mark VII atomization system, which is used with all current Agilent AA instruments. However, the tips and practices included within this document also apply to the atomization systems of earlier models.
Safety Warning: Extinguish the flame and ensure that the burner is cool before removing it.
3. Loosen both of the spray chamber retaining screws. Pull the complete spray chamber sideways until it is clear of the mounting and remove from the instrument. Tilt it sideways so that the liquid inside drains to the waste vessel, then detach the drain tubing from the liquid trap.
4. Remove the liquid trap by holding the nebulizer/spray chamber assembly firmly with one hand, while twisting the liquid trap in a clockwise direction to unlock it, as shown in Figure 1.
Figure 1. Twist the liquid trap clockwise to unlock and remove it.
5. Unscrew the plastic drain tube from the bottom of the nebulizer block.
6. Separate the nebulizer block and spray chamber by holding the nebulizer block firmly in one hand, while twisting the spray chamber in a counterclockwise direction to remove it.
7. Pull the pressure relief bung from the rear of the spray chamber.
8. Carefully remove the twin-headed mixing paddles through the rear end of the spray chamber.
9. Wash the spray chamber, liquid trap, pressure relief bung, drain tube, and mixing paddles thoroughly in laboratory detergent and warm water. Use a bottle brush to clean the inside the components. Rinse all parts thoroughly with distilled water and then leave the components to air dry.
Cleaning the Burner:
1. To clean the burner, you need to polish the inside of the burner slot. It is recommended to use a metal cleaning polish that is suitable for cleaning brass.
2. Insert the burner cleaning card into the burner slot and pour a small amount of the cleaning polish on each end of the card. Slide the card in and out of the burner slot several times to remove any deposits that may be present, as shown in Figure 2. The more you polish the burner, the better it is going to perform. You will get much better performance and much better resistance to blockage if you have a clean and well-polished burner.
Figure 2. Cleaning the burner slot with metal cleaning polish.
3. Rinse with distilled water, and place the burner inverted in an ultrasonic bath containing dilute laboratory detergent, for approximately 10 minutes.
4. Dry the burner, using an air or nitrogen purge before refitting or using the burner.
5. If there are stubborn deposits on the burner slot, you can soak the burner in a dilute nitric acid solution, then rinse the burner with de-ionized water and polish again before use.
Removing and Cleaning the Nebulizer Components:
1. Unscrew and remove the capillary adjuster thimble and locking ring. Fit the recessed end of the nebulizer tool over the capillary assembly and unscrew. Then carefully remove the components from the body, as shown in Figure 3.
Figure 3. Removing the capillary assembly and nebulizer components.
2. Before removing the venturi, loosen the clamping screw securing the impact bead in the adjustor block, and move the bead to the side.
3. Push the venturi out of the spray chamber body from the inside, using the nebulizer tool.
4. Place the nebulizer components in an ultrasonic bath containing a dilute detergent solution, and sonicate for 5-10 minutes. Rinse the nebulizer in distilled water, then allow to dry.
Reassembling the Nebulizer and Refitting the Spray Chamber:
1. Place the venturi into the nebulizer block and use the nebulizer tool to place it into position, as shown in Figure 4. Carefully insert the capillary assembly, O-ring end first, through the spring in the nebulizer body.
Figure 4. Placing the venturi into the nebulizer block.
2. Place the capillary guide into the nebulizer body.
3. Carefully guide the locking thimble over the capillary and screw it in place.
4. Push the impact bead into the nebulizer block, and position it so that the gap between the bead and the nebulizer venturi is about the thickness of a piece of paper. Carefully tighten the impact bead locking screw. Turn the impact bead adjuster counterclockwise until the bead appears midway in the cut-out of the nebulizer block.
5. Insert the mixing paddles into the rear opening of the spray chamber. Align the mixing paddles so that an opening between any 2 of the blades is at the bottom. Check that the paddles are still positioned correctly, and then push the paddles back into the spray chamber, until stopped by the shoulder.
6. Rinse the O-ring of the pressure relief bung with distilled water, and then refit the bung into the spray chamber until it is seated in place. Check that the O-ring is in position in the recess of the nebulizer block, and then connect the other end of the spray chamber to the nebulizer block. Use a clockwise, twisting motion to lock the spray chamber in position. Screw the drain tube, with the integrated float, into the bottom of the nebulizer block. Insert the float into the liquid trap, and secure the trap using a counterclockwise twisting motion to engage the bayonet fitting. Place the spray chamber and nebulizer assembly in position in the sample compartment, so that the fuel and oxidant outlet nipples are engaged correctly in the ports of the nebulizer block. Push the assembly firmly sideways and tighten the retaining screws. Refit the drain tubing to the waste container. Fill the liquid trap with distilled water through the opening for the burner until the liquid just overflows from the lower outlet of the liquid trap.
7. Refit the burner and ensure it is in position. Optimize the burner position vertically, horizontally, and rotationally using the burner alignment card.
8. Refit the flame shield and chimney.
For more information, see the following video: Troubleshooting and Maintenance of Atomic Absorption Systems: Part 2 - Flame Atomic Absorption