SEM-EDS needs a series of pre-requisites to yield relevant enough quant results : quantification requires a model to be applied after counts for each elements have been determined (ZAF, PhiRhoZ, XPP...).

All have in common that they will work only if the sample is :

• dense (not porous)
• conductive (electrically)
• homogeneous (no phases or large enough phases that they're locally one homogeneous material)
• isotropic (no orientation)
• thick enough for the interaction volume to stay within the material

If your sample does not fit those requirements, forget about using SEM-EDS as an elemental quantitative technique.

Also, limit of detection by SEM-EDS is ca. 0.1% atomic as a general rule of thumb. If you're looking for traces below that, forget it.

Given the nature of your sample and the target elements, I personally would go for alkaline fusion to prepare a fused disk and use XRF. If issues, digestion followed by ICP.

I just want to subtract "conductive" and "isotropic" from the list of Pierre Caulet . Non-conductive specimens could be coated with carbon with no serious limitations to trace element analysis.

SEM-EDS can only identify the elements present in the sample which is a rough idea to get the chemical composition present in your sample. for the precise measurement please do XPS which will you give the oxidation states and chemical composition present with the exact concentration.

XPS is a surface technique and while it would give interesting information about elements and their binding states, I do not recommend it for global bulk elemental analysis.

In XPS you can check the elements present in bulk by etching using the ion beam. And for bulk you can perform Raman spectroscopy which will give the idea about the elements present but not with the exact concentration.

The analysis volume of XPS is very small, even with etching. I do agree this would be a good technique if working on single nano-hydroxyapatite particles or small clusters. Still not representative enough if you want a relevant analysis on larger sample sizes.

(Plus, XRF is much less expensive)

Dear Sri Aurobindo Panda , EDS is quite capable of quantitative analysis. You know, the same rifle in hands of two hunters can produce quite different results.

That depends on the quantity and the thickness of the sample (can disregard of your sample is homogeneus). Depending on the accleration voltage you use, the area of point mode would cover ajout 300nm (at 5kv) to about 2.5 microns (at 30kv) in radius. Same can be said about the depth of penetration. If you can keep the sample in that area, it would be quite accurate. Please note that EDs is a semi quantitative method and the total % of element present will always be 100%.therefore the homogeneity/coverage area of the sample is very important. Other than that, it could only detect from border n to U element.

One more thing… the cincentration need to be about 1000-2000ppm or in the range of 0.1-0.2%