%1 olması gerekiyor.

The value of 1 atomic-% is a number that should give you a "feeling" what the method is capable of.

The main problem is to get a good spectrum, i.e. to identify the peak for the minor element with good signal-to-noise ratio.

Modern EDS software will often give a confidence interval for the concentrations calculated from the signals and the underlying model.

Some reading:

Dale E. Newbury: https://doi.org/10.1002/sca.20151

Dale E. Newbury, et al., Is Scanning Electron Microscopy/Energy Dispersive X-ray Spectrometry (SEM/EDS) Quantitative?, SCANNING 35: 141-168, 2013

https://doi.org/10.1002/sca.21041

Dale E. Newbury: Energy Dispersive Spectrometry, in: Characterization of Materials, pp1-26.

https://onlinelibrary.wiley.com/doi/abs/10.1002/0471266965.com087.pub2

I heartily concur with Stefan Baunack. For such a question, it would be good to refer back to the basic texts and Dale Newbury is a very good place to start.

Note that the detection limit is normally given in mass%, not atomic%. It can make more than an order of magnitude difference. A Cd atom is 10x heavier than a C atom. So the same number of atoms that give 1% Cd would give 10% C.

Detection limit depends a lot on the noise in the spectrum. If you cannot distinguish the peak from the background, then you cannot detect it. Noise is determined by count and reduces with the square root of the count. So, if you have 1% detection limit under one set of conditions, counting four times more x-rays will reduce the detection limit to 0.5%. You can count longer or faster; it is the count that matters.

I normally run our EDS at 15 kcps. I can see a detection limit of 0.1 wt% in 30 seconds provided that there are not overlapping peaks. What are your conditions?

Thank you very much for the answers

Stefan Baunack I will go through the resources for a deeper understanding for sure.

Warren Straszheim I need to study a little bit more to answer your question, I think.

I had another question in mind - why is the x-ray peaks are proportional to the wt% of the corresponding elements present in the sample ?

X ışını elementin proton ve nötron sayısını belirler. Bu sayede elementin kütle numarası ve atom numarası belli olur. Element x ışını yaydığı zaman kütle ve atom numarası buna bağlı olarak değişir.X ışını yoğunluğu atomun ne kadar yoğun olduğunu ve ne kadar ışıma yapması gerektiğini gösterir. Bu sayede atomda ne kadar fazla proton ve nötron olduğu anlaşılır. Elementin kütle numarası saçılan x ışını sayısına bağlıdır. Bu yüzden atomun ağırlıkça yüzdesi belirlenebilir. X ışını sayısı elementin proton ve nötron sayısını belirler.

Şükrü Aktaş still out of my understanding. x-rays that are influenced by the nucleus of the atom are the bremsstrahlung x-rays-are you talking about these ? Then, i kind of get it.

But, EDS(SEM) x-rays are characteristic x-rays that are plotted as counts vs energy (keV). Then, wouldn't it be easier to mactch those x-ray energies with the recorded x-ray energies that could be emitted by the corresponding species in the sample and therefore the atomic percentage?

Shortly, the intensity of a given X-ray line is proportional to the number of atoms in the excited volume.

To describe the emission, several processes (primary electron stopping, ionization of the atom, X-ray emission, X-ray fluorescence have to be taken into account; see ZAF-correction).

Some of these process are described by formulae where the mass density is taken into account.

If your sample consists of more than one element (mixture, alloy, compound) both abundance of the atom (% of all atoms, molar fraction) and their spatial density (atoms/µm³) are unknown and must be deduced from the measurement.

Both mass density (g/cm³) and number density (atoms/cm³) or of your sample are unknown and will be calculated in an iterative process, but may be differ from the value of a bulk sample (thin film, defects, vacancies,…)

In case of a mixture for the stopping process an average atomic number will be used (these are all models!).

“From isotope measurements (Donovan and Pingitore 2002, Donovan et al. 2003), we also know that the physics of EPMA is electrodynamics based, not mass based.

The use of mass is simply a holdover from early days of chemistry, when the scale balance was the primary tool of science! (that‘s only a slight exaggeration!)“

https://probesoftware.com/smf/index.php?topic=1221.msg10192;topicseen#msg10192

Excuse me, Şükrü Aktaş , but I have no idea where you got your answer. Your comments may have some relevance to x-rays, but not to EDS. I don't read Turkish, so I resorted to Google Translate. Did it render a decent translation? If so, I have MANY issues with your answer. I cite a couple.

"X-ray determines the number of protons and neutrons of the element. In this way, the mass number and atomic number of the element are determined. When the element emits x-rays, its mass and atomic number change accordingly. The x-ray density shows how dense the atom is and how much radiation it should emit. In this way, it is understood how many protons and neutrons there are in the atom. The mass number of the element depends on the number of x-rays scattered. Therefore, the weight percentage of the atom can be determined. The number of x-rays determines the number of protons and neutrons of the element."

EDS determines the energy and abundance of the characteristic x-rays to determine the element, so in that way, you might say it is determining mass and atomic number. But the energy depends more on atomic number than on mass. I understand different isotopes will have the same energy.

The number of x-rays determines the abundance of the element, not its mass or atomic number. The energy determines the electronic structure of the atom, thus telling us about the number of protons.

Abdul Quader , my question was about the conditions used for your measurements. That is something the SEM-EDS operator should be able to tell you, whether that is you or someone else. That is not something to study, per se.

The count rate and acquisition time will have a lot to do with your question of detection limit. Peak overlaps will also be important. It would be helpful to see a typical spectrum.

I cannot tell you with great certainty why the intensity is related to mass fraction instead of atomic fraction. However, I will hazard a good guess that the intensity is likely a function of the number of electrons in the orbitals. The more electrons, the more protons, and thus the more mass.

I have included a couple practical examples below taken from standard materials analyzed on our system.

The first is for HgS which is 86 wt% and 50 at% Hg. The Hg M-integral is about 3x the S K-integral. The intensity ratio is more like the mass ratio.

The second is for Nd2Fe17 which is 23.3 wt% 10.5 at% Nd. The peak ratio is not quite 4:1 which is more like the mass ratio.

Of course, there are various corrections involved so that the numbers are not exact.

Işıma sırasında atom ve kütle numarası ayırtedici bir özelliktir. Bu yüzden atomun dalga boyu miktarı ve aralığı farklı olur.

I translated your answer to "Atomic and mass number are distinguishing features during radiation. Therefore, the amount and range of wavelengths of the atom are different." Is that a fair translation? I would prefer to conduct the conversation in English.

I am not sure how to take the first sentence. I fear something is lost in translation. Atomic structure, which relates to atomic number and mass, determines the energy/wavelength of the x-rays. So, yes, the "RANGE" of wavelengths will be different (characteristic) for each element.

The "AMOUNT" of x-rays within a line series is determined by the electronic structure. But the amount of Cd vs. Yb x-rays depends on the relative abundance of the elements. So which are you referring to? The original post was asking about detection limit which is the latter issue.