This Information Applies To: 5100, 5110, 5800, and 5900 ICP-OES instruments
ICP-OES plasma ignition may fail due to various reasons, but often the user can resolve this issue quickly. This document examines how to troubleshoot when the plasma ignites and then goes out, or does not light at all.
Steps to follow:
The following steps are recommended for troubleshooting ICP-OES plasma ignition:
- A main reason why the plasma will not light is that excessive air has entered the plasma. Check the following:
- The peristaltic pump tubing is not clamped or does not have sufficient clamping pressure. Usually, air is being pulled into the nebulizer because the pump tubing is not properly clamped during ignition. At ignition, the plasma is sensitive to too much air being self-aspirated into the plasma.
- Check that the autosampler probe is down inside the rinse vessel and that the rinse solution is flowing properly to the nebulizer.
Safety Warning: Always wait for the torch to cool before removing it from the torch compartment.
- The torch may be damaged, dirty, or not assembled correctly. Try a new torch. If the torch end is highly contaminated it can become conductive, making plasma ignition less consistent.
- The torch contains liquid sample- clean and dry torch.
- The nebulizer may have some damage and is leaking.
- There may be a leak at nebulizer gas fitting. Check to ensure the nebulizer gas tubing from the instrument to the nebulizer fitting (Figure 1) is tight and secure.
Figure 1. Nebulizer gas tubing and fitting.
- The spray chamber is not draining properly. If the spray chamber is not draining properly, due to insufficient pressure on the peristaltic pump pressure arms, then water droplets will go up into the torch and prevent ignition. Also check the drain tubing fitting (Figure 2) to ensure that the rinse solution is flowing out the spray chamber properly. Always check the torch to ensure it is clean and completely dry.
Figure 2. Drain fitting on spray chamber.
- A large droplet may have entered the plasma. Ensure spray chamber is clean and nebulizer is working correctly. If using a single pass spray chamber, consider changing to a double-pass spray chamber.
- Insufficient plasma flow and/or excessive auxiliary flow.
- Work coil damaged and bent down.
- Problem with ignitor- Is it possible to see the ignition spark? Is it possible to hear the sound during a normal ignition?
- Has anything in your system changed? For example, has a new argon cylinder been connected to the instrument?
- Ensure that the argon gas supply pressure is correct, and remember that the recommended pressure range is from 500 to 600 kPa (from 73 to 88 psi). It is better to set the pressure at the regulator to 600 kPa (88 psi) due to possible line pressure drops.
- Ideally a second regulator has been installed within three meters or 10 feet of the instrument. If running 30 m of 6 mm or 1/4" ID tubing to the instrument at 500 kPa, the line pressure drop is adequate to affect plasma ignition. If possible, watch the regulator (Figure 3) while trying to ignite the plasma, and watch to ensure that the pressure doesn't fall below 80 psi. You may need to raise the pressure if this happens.
Figure 3. Argon pressure regulator.
- Unclamp and remove the spray chamber from the bottom of the torch. Seal the bottom of the torch with Parafilm and attempt ignition. This eliminates possible sample introduction system leaks or other issues with the nebulizer and spray chamber.
- In case ignition is working with isolated (sealed with Parafilm) torch, check the nebulizer / spray chamber for tightness, in particular the helix seal (Figure 4).
Figure 4. Helix fitting between nebulizer and spray chamber.