Why can't carbon and nitrogen be detected in ICP-MS and ICP-OES techniques? Why can't carbon and nitrogen be detected in ICP-MS and ICP-OES techniques?

My book says this technique is efficient for detecting multiple elements, with exception of halogens and carbon. I found somewhere that ICP is an open system, therefore it doesn't allow carbon detection. But why is that exactly?
As you say, air is allowed to enter the plasma. Air consists primarily of $\ce{N2}$ and $\ce{O2}$, and would clearly interfere with any oxygen or nitrogen in the sample. The problem is not that ICP-MS or -OES cannot detect them, the problem is air.