May be you'll find this useful:

Preparation of biological specimens for EDS with an SEM

​https://www.oxinst.com/blogs/preparation-of-biological-specimens-for-eds-with-an-sem

Tips and Tricks for Biological EDS

https://nano.oxinst.com/library/past-blogs/biological-eds-tips-and-tricks

Advanced techniques in SEM and EDS for biological samples​https://www.selectscience.net/expert-insight/advanced-techniques-in-sem-and-eds-for-biological-samples/?artID=56957

If you do not see any charging, you usually can perform qualitative and semiquantitative EDS analysis. Just check if end of a spectrum tail (background) coincides with accelerating voltage (it is a check for charging). Quantitative EDS analysis of a biological specimen is quite complicated. Could be used for comparison of heavier elements concentration in betwin specimen series, but for light elements its mostly useless.

Adding a coating to samples studied by Scanning Electron Microscopy with Energy Dispersive X-ray Spectroscopy (SEM-EDX) is a common practice for several reasons:

Conductivity Improvement: Many samples are insulators, meaning they do not conduct electricity well. When subjected to the electron beam in SEM, insulating samples can accumulate charges, leading to distorted images and inaccurate results. Coating the sample with a thin layer of conductive material (such as gold or carbon) helps dissipate these charges and improves the overall conductivity.

Improved Resolution: Coating the sample can enhance the resolution of SEM images. The coating provides a smooth and conductive surface, reducing electron scattering and improving image clarity. This is particularly important for obtaining detailed and accurate morphological information.

Enhanced Contrast: Coating can improve the contrast of the sample, making it easier to distinguish different features and elements. This is especially beneficial for samples with low natural contrast.

Prevention of Contamination: Coating helps protect the sample from contamination during the imaging process. It forms a barrier that minimizes the impact of environmental factors, such as moisture and gases, which could affect the sample and compromise the quality of the analysis.

X-ray Detection: In EDX analysis, the coating can influence X-ray emission and detection. A conductive coating can enhance X-ray signals, making it easier to identify and quantify the elemental composition of the sample.

While coating is advantageous in many cases, there are situations where it may not be necessary or could interfere with specific analyses. The decision to coat or not depends on the nature of the sample, the objectives of the analysis, and the instrument specifications.

In case you are using an Environmental SEM system, then there is no need to add a coating, because you can accomplish that through the control of the moisture level in the ESEM.

Dear Bahram Roughani , chatbot you used to generate your post did not understand the question. You are damaging RG polluting it with nonessential answers.

Dear all

Stefan Baunack thank you for all websites which are helpful. Vladimir Dusevich can you please explain me how to check charging on spectra? How spectrum tail (background) should coincidence with accelerating voltage? This is new for me. I am interesting in Cd, Fe, S and K, are they heavy enough to be measured by EDS?

Thank you

Jan

Your elements of interest are heavy enough. As I understand they are in organic matrice. Ignoring it's elements (C, O, etc.) will skew results, but supposedly in the same way for all of your specimens, so it may be suitable for comparison purposes.

Checking for charging. Suppose you use 15 kV accelerating voltage. Then tail of backgroung radiation of spectrum should became 0 at 15 kV. If it goes to 0 earlier (say, at 12 kV), than you have charging.

Thank you Vladimir Dusevich, now I understand how to check charging.

If I understand well first part of you answer, you suggest to make result table and calculate weight % without C and O (exclude them)? Is it because C and O are not preciselly measured (as light elements) and if they are included the overal calculation is not so correct? And if C and O are excluded there is still some error, but as Cd, S, Fe, K,..etc are heavy elements, the measurement and results are more correct (and some possible errors are same for all measurements). Is my assumption right or not?

Thank you

Jan

Gold coating your specimen prior to EDX analysis will block low energy x-rays from reaching your detector. If charging occurs on a biological specimen prior to EDX analysis, coat it with a thin layer of carbon in a vacuum evaporator. If the specimen isn't charging, go ahead with the analysis.

What I meant was exclude C and O from reporting their quantities, unless you are perfroming full analysis with standards.

Thank you Vladimir Dusevich and Ronald Hathaway

Now I understand

Jan