# How are samples prepared for analysis with ICP-OES? Can it analyse gases?

In ICP-OES (Wikipedia page), you introduce a sample into a very hot plasma and then run a spectral analysis on the resulting light emissions. Liquid samples are sprayed into the flame. From the Wikipedia article:

A peristaltic pump delivers an aqueous or organic sample into an analytical nebulizer where it is changed into mist and introduced directly inside the plasma flame.

From that I can imagine that you would probably dissolve solid samples (the technique is widely used in metallurgy and mineralogy) in something suitable to obtain a liquid sample. If that's correct, I'm wondering how the feeding apparatus is constructed to withstand possibly aggresive solvents, like nitric acid or aqua regia. The injection tube is apparently made from fused silica, I guess that's a probable material for the feed as well.

And how about gases? Are they analysed with ICP-OES as well? Are they simply pumped into the injection tube? For example, can we just introduce a stream of air into the plasma and get the emission spectrum for 78% nitrogen, 21% oxygen (I guess the argon will be hidden because the plasma gas is argon)? I guess since every sample will be beyond vaporized anyway by the intense heat, it can't make much difference, but are gas samples too "thin", i. e. do they contain too little atoms per volume for useful analysis?

• From that I can imagine that you would probably dissolve solid samples in something suitable to obtain a liquid sample. Under normal circumstances, that is absolutely correct. As mentioned on the answers, acids are not a problem - in fact, concentrated acids are usually used to "digest" organic samples in sample preparation. Then the samples are diluted to be suitable for the ICP. There's a whole science behind sample preparation, though. Each sample and each analyte require very specific sample preparation methods in order to be properly detected in equipments such as an ICP-OES. – Alex Apr 18 '13 at 16:55

Injections tubes are indeed often made out of fused quartz. Dealing with aggressive solvents is actually not that much of an issue because of the extremely low amounts of material that can be detected with ICP-OES. Therefore, you can simply dilute your aggressive solvent before use. You can look for example at this research note where they dissolve a sample in $\ce{HCl}$ and $\ce{HNO3}$ and then dilute it before use.