I've used ICP-MS in the past for examining elements in the thin films and noticed that HNO3 seems to be the gold standard as an etchant. I wasn't able to find much information as to why this is so thus wanted to ask if anyone knows why?
Hello Jea,
In this past ICP-MS users avoided (as much as possible) the use of acids other than nitric acid as the backgrounds were not much higher for the majority of elements in comparison to other acids such as HCl. The problem with older ICP-MS systems was simply the issue of interferences and adding an additional matrix interference would cause even more variability to key elements - e.g. the Cl component formed interferences on V and As amongst other elements (as ClO and ArCl polyatomics).
With the introduction of collision/reaction cells (CRC's) and depending upon the technology the use of acids such as HCl should be routine as the CRC eliminates or significantly reduces the backgrounds from the polyatomic interferences.
This is in fact a great benefit as not all elements are stable in a matrix of only HNO3 or many elements are not efficiently extracted. The use of HCl is probably one of the greatest advantages of modern CRC-based instruments due to the improvement in stability and washout for elements such as Hg, Mo, Sn, W and many more.
So whilst you are not exactly wrong rreally your question sould only apply to older ICP-MS instrumentation.
Kind Regards,
Glenn Woods
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