Unfortunately many analysts' just 'jump' on an instrument without thinking 1st! Does the molecular target have a UV chromophore? In this case a PDA or DAD detector may be more appropriate.
Is the target molecule stable?
Why MS or MS/MS? It is the molecular target that determines the detector. They are appropriate if the sample matrix is complex (like a food) or the expected concentration is low (like sub ppb or ppt).
Sample preparation for analysis is a separate discipline. The sample preparation procedures are not distinguished by the detection option. The method is selected for analyte mainly and for the purpose of analysis.
If you can explain a bit about what is the sample to analyse, e.g small molecule, protein, etc. then it will be easier to advice and explain. what is the most suitable option, depending on the instrument on hand as well
Selection of the method depends upon your sample and purpose of analysis. The nature of sample matrix is also an important factor to be considered.
Thank you all for your scholastic answer. I am actually a layman in chromatography. But, in my next experiment I need to analyse Maximum Residue limit of Pesticides (MRLs) and my professor said you do it either GC-MS or LC-MS or GC-MS/MS or LC-MS/MS? So, I seeks your help to choose which one will be the convenient one for the beginner?
Both the techniques can be used. As a layman in Chromatography, it will be easy for you to optimise the method in GCMS. GCMS/MS will be beneficial for high matrix samples and you can get rid of matrix interference so that the target can be precisely quantified. Once you are very familiar with GCMS, using GCMS/MS will be easy.
Ha Ha Ha! In the past, I wouldn't let a student near a chromatograph! Try getting 10 years of experience 1st.
As a layman you will not have any success at all with pesticides in food. It is one of the hardest experiments in chromatography that you can perform. I doubt that your professor used the word "either" as you need both GC-MS and LC-MS/MS for successful pesticide analysis. You need to start with the basics in chromatography, which would be GC-FID and HPLC-UV and then graduate from there once you have learned how chromatography works.
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