The sample introduction system of an inductively coupled plasma (ICP) spectrometer carries a liquid sample from the autosampler to the ICP spectrometer. The components that make up the sample introduction system include nebulizers, spray chambers, torches, radiofrequency (RF) coils, and, with an ICP mass spectrometer, ICP/MS cones. If any of these components do not function optimally, they can be the cause of significant measurement errors. These errors can be mitigated or avoided by selecting the appropriate components for the sample to be analyzed and by practicing proper care combined with regularly scheduled maintenance.
Selection, care, and maintenance are all key to reducing ICP spectrometer downtime and laboratory overall costs.
Nebulizers
The function of a nebulizer is to convert a liquid sample into an aerosol for introduction into the plasma. The aerosol facilitates uniform sample introduction for both a reproducible signal output and stable operation of the plasma.
Poor nebulizer performance may be due to nebulizer blockage from salt deposits or a drop in the nebulizer backpressure due to the hardening of the argon supply tubing. Damage control and proper care and maintenance can keep nebulizers operating at peak performance.
To care for nebulizers:
- Treat the borosilicate glass or quartz nebulizer with the same attention as glass labware
- Unblock the nebulizer and clean with a solution such as Eluo HF cleaner or standard Eluo cleaner
- Soak the tip of the nebulizer in a 25% Fluka solution (4× dilution); then flush with warm water and methanol to dry to remove stubborn salt deposits
- Replace the gas supply tubing
To prevent damage to the nebulizer, do not:
- Insert wires and probes into the nebulizer tip
- Touch the tip with bare hands
- Use HF to clean a glass or quartz nebulizer
- Place a glass nebulizer into an ultrasonic bath
- Use hot liquid to flush the sample capillary.
More information can be found here.
Spray chambers
Spray chambers are used to remove the droplets produced by the nebulizer.
The formation of salt deposits and crystals inside the spray chamber may impede spray chamber performance.
Care and maintenance steps are as follows:
- Treat the spray chamber with the same care as glass labware
- Start and finish use by nebulizing a mildly acidic blank solution for several minutes
- Clean the spray chamber with a 2.5% Fluka solution (40× dilution) for 15 minutes
- Soak overnight in a 25% Fluka solution (4× dilution) or in 25% strength RBS-25 solution (4× dilution)
To prevent damage to PTFE and PFA spray chambers, do not:
- Use H2O2 for cleaning
- Allow physical contact of the chamber interior surface with any instrument
For more information on care and maintenance of spray chambers, click here.
Torches
The function of a torch is to create and sustain the plasma, evaporate the solvent from the analyte salts, atomize the atoms in the salt, and excite or ionize the atoms.
Reduced torch life may result from contamination by salt deposits, organics, and metals on the surface of the quartz combined with high temperature.
As with other system components, routine care and maintenance are necessary.
To care for torches:
- Remove salt deposits by soaking the torch or outer tube in a 25% Fluka solution (4× dilution
- Remove organics by burning off the carbon with a handheld propane torch
- Remove metals by soaking in acid (with the exception of HF).
To prevent torch damage, do not:
- Use HF for cleaning
- Knock the torch against hard objects
- Leave the torch unprotected when not in use
- Touch the torch with bare hands
- Use metal or ceramic brushes or scraping or other abrasive tools
For more details on torch care please visit here.
RF coils
RF coils transfer the RF energy to the plasma and induce a heat source.
Corrosion of the coil base metal reduces the efficiency of energy transfer to the plasma. Plating the base metal with silver or gold may address the corrosion issue, with potential drawbacks, with silver-plating tarnishing and gold-plating showing signs of copper sulfate formation over time.
Care of the RF coil involves periodically cleaning the silver-plated coil with a tarnish remover and cleaning the gold-plated coil with an abrasive metal polish that is free of acid.
Visit here to learn more about RF coil care and maintenance.
ICP/MS cones
ICP/MS cones are the differential apertures in an ICP/MS system. Their function is to separate the sample at atmosphere from the mass filter and detector at high vacuum.
Reduced ICP/MS cone life may be due to the cone orifice being blocked or distorted.
Cone cleaning can be done by one of three methods:
- Soaking in Citranox daily or weekly, depending on application
- Sonicating in Citranox daily or weekly, depending on application
- Sonicating in nitric acid weekly or monthly, depending on application.
Accessories
Several ICP accessories can be added to the components of a sample introduction system to enhance their care and maintenance. Visit here for more information on ICP accessories.
Conclusion
Proper care combined with regularly scheduled maintenance of the components of an ICP sample introduction system will help maintain optimum performance and increase lifetime, thus reducing component replacement costs.
For additional information on ICP sample introduction components and their care and maintenance, visit here.