Mr. Elagamy,

What means ''theoretically' when part of your parameters are determined by the operator on the base on the ionization efficiency? Have you basic knowledge of MS?

There are some tabulated values for the expected fragments mass,collision energy and ionization mode for some certain compounds I guest need to use it as guidelines

Mr. Mr. Elagamy,

Yes, but there are a lot of important data such as runtime, concentration, internal standard type, etc.

I just need to predict the parent and fragment masses of some certain groups of pharmaceuticals

Mr. Elagamy,

As I have written before most probably you have not basic knowledge of mass spectrometry, even most probably not only. Your first and latter questions uderline namely this fact.

Because of, how to obtain masses of parent ions can be found in the textbooks devoted to Analytical Chemistry. The question can be rephrased: How to obtain the mass of your compounds in its cationic, respectively, anionic forms (parent ions?) The answer is: By means of calculator and periodic table of the elements.

Towards obtaining of masses of simple fragment ions, you also need calculator and periodic table, but as well as, again, basic knowledge, which can be found in, for instance, J. Gross, Mass Spectrometry, textbook, Springer Verlag, Berlin Heidelberg, 2017, pp. 1-968 (in particular, pages 128-146).

Whatever you want to predict, wrong or right, you still have to prove it experimentally anyway. So, why waste the time to predict something you don't know if it is true or will happen and walk straight to the lab and tune to compound yourself. It is like your are trying to predict how your date will be like just looking at the picture instead of talking to the person and getting to know that person yourself.

Looking up on literature studies where structurally similar compounds have been analyzed will probably give an idea of the expected ionization and fragmentation pattern of your compounds of interest. However, the specific parameter values as far as ionization is concerned (collision energy, cone voltage,......etc) will be a variable as these values are "user based" to "fit the purpose" of their analysis. Keep in mind also that these values or even the ionization behavior can vary across various brands or models of the analytical instruments.

Kindly go through the following weblink : https://massbank.eu/MassBank/index.html

Check whether your compound of interest is listed. If so probably you can get all the details. Basically, the fragmentation voltage needs to be optimized and it varies across compounds. Theoretically, if the compound you want to study is known, then look for possible publications that tells about the collision energy that they have used.

Hope this helps,

Best,

M

Finally I have got some helpful tips, thank you all. Actually my problem was a failure with the pump that why I couldn't get it experimentally ... for sure there are data in the literature but not for all compounds

Finally I have got some helpful tips, thank you all. Actually my problem was a failure with the pump that why I couldn't get it experimentally ... for sure there are data in the literature but not for all compounds