第1楼2005/03/23
Torches
The two basic torch designs are the Greenfield and Fassel torches. The Greenfield torch requires higher gas flows and RF powers. The Greenfield torch is more rugged (less likely to extinguish due to misalignment and introduction of air) whereas the Fassel torch requires less Ar and power. Both designs produce similar detection limits.
Some nebulizer designs work better with one torch design over another. Before experimenting with torches, it is best to contact your instrument manufacturer to determine the torch design recommended for your instrument as well as any design specifications, operating conditions, and dimensions that must be observed.
Considerations
The following are some questions you may want to consider, whether you are looking to purchase a new ICP or already have one or more existing units:
What torch design is used and what are the power and Ar gas flow requirements? (It may be helpful to calculate/determine your annual Ar expense).
What nebulizer and spray chamber designs are available and can they be obtained from alternate suppliers?
Are there specific nebulizer designs that cannot be used with the recommended torch/spray chamber?
What are the costs of the individual introduction system components and what are the upkeep costs over a year of operation?
What is the lifetime of the torch and what is the most common reason for failure?
How tolerant is the system to slight changes in torch alignment?
How tolerant is the system to air coming from the nebulizer and will it extinguish after a few seconds?
How tolerant is the system to the introduction of organic solvents?
What is the lowest boiling point solvent that can be introduced?
How tolerant is the system to the torch building up coke for aromatic and aliphatic non-polar solvents?
What is the most precise nebulizer that can be used with your ICP and what precision should be obtained?
What are the detection limits for your analytes of interest? Are you achieving the detection limits required for your application?
When looking for lower detection limits have you considered axial view ICP? Ultrasonic nebulizers? Both?
Do your analytical solution samples contain high levels of dissolved solids? Do they contain any suspended solids?
Do you experience nebulizer salting out or plugging?
Which high solids nebulizer is recommended for your current or potential ICP and what is the precision to be expected? How rugged is it and what does it cost?
How difficult is it to connect an ultrasonic nebulizer?
Can either the Scott or Cyclonic spray chamber designs be used?
What are the washout times for Hg, B, Y, and Cu in nitric acid? In HCl?
Are corrosion resistant/HF resistant introduction systems available? What do they cost? How easy are they to switch in and out?
When analyzing for Si in trace HF, how much of a Si, B, Na, and, Al background signal do you get?
If the introduction system contains glass, how much HF can be tolerated before signals from Si are observed? What about before damage occurs?
In the next section sample introduction compatibility and precision issues will be addressed.