Hi, Actually yes, sometimes you need to make more runs of the same sample to confirm and report a mean.

http://www.micronanalytical.com/sem.html

Have you used standards? Standardless quantitative analysis for C and O is in most cases meaningless.

Height of peaks depends on many variables, one of which is amount (percentage) of element.

Dear Kashmiri Deka

Did you coat the samples?

If  yes, inappropriate coating procedure will make this phenomenon.

For EDS analyses, you should not coat the samples.

Dear Kashmiri Deka, EDX that you performed was with which instrument (TEM/SEM)

I agree with Vladimir about this. Quantifying light elements with X-rays needs very careful work and better results will come from a calibrated system using standards that have been measured in the same instrument. Modern standardless software or 'virtual standards' packs are ok for ball park figures and are improving all the time, but should not be used for serious quantitative work. 

Some things also to consider. Is your prepared sample homogeneous within the interaction volume? Did you do spot or area measurements?

Is the sample prepared flat and highly polished?

The phi-rho-zeta matrix corrections may be better for light element analysis than ZAF.

To answer your initial question the intensity of the peaks is more likely to be proportional to the concentration in a TEM, but in the SEM it is not always the case. In the SEM the intensities are not directly proportional to concentration.

I advice you to know about some limitations of EDS/EDX technique so as to understand the technique well......

[The following is an extracted info from Myscope - ammrf ]

1] Light elements (Z < 11) cannot be routinely analysed by EDS.

Hydrogen (Z = 1) and He (Z = 2) do not have Characteristic X-rays, and the Li (Z = 3) K X-rays are of too low energy to be detected by EDS.

2] Beryllium (Z = 4) to Ne (Z = 10) X-rays can be detected by EDS, but there are two problems. Firstly, they are low energy X rays subject to strong absorption by the specimen. Secondly, the electrons involved in generating the Characteristic X-rays are also the valence electrons involved in the chemical bonding of the element, therefore the shapes and positions of the peaks may change in different compounds. The samples and the standards must be closely matched for best results. 

3] Carbon is the most commonly used coating material for non-conductive samples and cannot be analysed if the sample is carbon coated. A different coating material must be used if analysing for carbon.(carbon coating of materials may enhance its presence, if you have used C-tape in SEM )  

4] Many minerals contain oxygen bonded with a range of cations. It is common practice to calculate the amount of oxygen in the sample by measuring the percentages of the cations and calculating oxygen by stoichiometry. This generally is more accurate than analysing for oxygen.

5] Calculating oxygen by stoichiometry requires knowledge of the valence state of the cations to which it is bonded. This information is not available from EDS analysis

6] Some samples may contain structurally bound water or carbonate. Complete analyses of these samples cannot be derived by EDS analysis.

Hope it helps

Fully agree with Hameed's explanation. The important points are as follows: (i) it's difficult to precisely quantified the light elements in a heavy matrix due to absorption effects.(ii) Try to use a right Acc. voltage if you are using high voltage then the excitation volume will be large and  this will limits the quantification. (ii) For EDX the sample should be clean, sometimes if your sample is not clean than it will show a huge carbon peak in your measurements which is meaningless.

A straight answer to the original question is Yes. However the answer needs to be formulated as follows: the area of an EDX peak of an element in a sample is directly proportional to the abundance of the element in the sample. This does not necessarily mean that all elements' peaks in a sample will correlate with one-another in a directly proportional way with the relative percentages of all the elements. This was in fact what the original question seemed to imply.

The reason for this stems from the interaction of the X-rays generated within the sample with the elements present in the sample. This interaction is usually referred to (and corrected accordingly) as the ZAF matrix effect. Where the three main effects of: Atomic number (Z), Absorption (A), and Fluorescence (F), have to be taken into account and they work in different ways for different elements...

For instance, in the case of the analysis of light elements (i.e., C) in the presence of heavier ones (i.e. Mn)  a proportion of the Carbon X-rays may come from their excitation from X-rays generated by the interactions of the electrons with Mn (Fluorescence). However, all other effects (Z, A) must also be considered and this is usually taken care of by the appropriate software programme (ZAF or Phi-rho-z). 

Naturally, quantification will also be achieved quite differently in the case of standardless or with-standard analysis. Plus all other conditions (instrumental and sample preparation) can also greatly influence the results.

Some of the comments above are also right, however I think the original question required an answer based on the basic principles of microanalysis (matrix effects) as a pre-requisite of the discussion.

Hi, EDS analysis is not suitable for seious quantification works for light elements. I agree with previous comments the relative K-alpha peak proportions works for TEM-EDS analysis for thin specimens, when the Cliff-Lorimer method applies, but not for SEM-EDS, when ZAF correction must be used. You should take into account the sample prep issues, and that the interactin volume is different for different elements, being larger for ligher elements. However, EDS quantification for light elements is not precise either for TEM or SEM analysis. The characteristic X-ray signal for light elements are not well defined electron transitions. If you still want to do spectroscopy analysis with high spatial resolution, I would you suggest do TEM-EELS for ligh element quantifications.

Regards,

Please, I have a question:

Does the Energy-dispersive X-ray spectroscopy (EDX or EDS) provide the chemical composition of the material as metal or metal oxide? i.e the results obtained from the EDX are in percent for metal or for metal oxide?

I found in different published papers that the data obtained from EDX are in % of metals and other papers as % metal oxide. When we use it as metals and when as metal oxide?

Is the following sentence right or false:  "EDX determines the chemical composition of materials as metals and exposes them as oxides but it doesn't mean that they are oxides". Many thanks for your reply.

Hi guys, may you please give me idea how to elaborate apparent concentration, intensity correction, standard level and factory standard by SEM-EDX? I attached the file here for your clear understanding.