Despite its major advantages MALDI is not usually considered a dependable platform for quantitative MS analysis over ESI. However the rapid advances and undeniable prospects of MALDI-Imaging in research and clinical applications - makes this objective theoretically significant and practically possible. I am inviting colleagues who share similar interests/experience.
Hi,
My feeling is that the capabilities of MALDI as a quantitative (imaging) MS technique mainly rely on the complexity of your sample (or the resolution of your MALDI-MS), as well as the availability of a suitable (e.g. stable isotope-labeled) internal standard for your analyte(s) of interest.
Hope this helps!
sure it can, with about 2 % CV near the equivalence point of heavy isotope standard and ~ 5 % at 1:10 or 10:1 ratios.
J Proteome Res. 2012 Mar 2;11(3):1868-78. doi: 10.1021/pr201092v. Epub 2012.
Label free MALDI is in the 20 % CV/accuracy ballgame:
Proteomics. 2011 Oct;11(20):3992-4006. doi: 10.1002/pmic.201100024. Epub 2011.
Mr. Ghosh,
MALDI is a high reproducible method for solid-state quantitation. The fact that it is not broadly implemented in analytical practice for LMW analysis, do not means that it is not quantitative method. It is associated mainly with biomacromolecular screening, and thus major methodological contributions are addressed to clinical diagnostics and in vivo imaging of macromolecules. For LMW analytes, there are implemented mainly hybrid MS variants involving ESI.
On the other hand to compare applicability of both ESI and MALDI methods for quantitation has no sense, generally. Because of ESI is method for quantitation in solution. So, those are essentially as physical phenomena, instrumentation, sampling, quantitaion procedure and so forth, two different instrumental methods.
Let's try to proof by contradiction, if the MS techniques (MALDI and ESI) were quantitative you should always have the same intensity/height of the peaks in each repetition of the analysis, for example, from a tryptic-digest of a certain amount of one protein. Moreover, each peak in the same analysis should have the same intensity respect to the other peaks (they come from the same number/amount of protein) but it is not.
So, in my opinion, for quantitative purpose, you should use different internal standards, one for each molecule you want quantify labelled by a different isotope, as already suggested by other.
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