I have a naturally extract melanin sample and mass spectra gives M value of 375 (peaks for M+1, M+23, 2M+23). Could it be any possible variant of melanin? There is an additional peak at 223 which I am unable to assign? Any help is appreciated.
Melanin C₁₈H₁₀N₂O₄ MW 318
The short answer is that it is impossible to say from the information provided. You basically have an unknown that may or may not be related to melanin. As a starting point you need a high resolution accurate mass to derive a chemical formula. Following that you will need to isolate enough material for 13C and 1H NMR.
Hi,
The M+23 Da species could be the sodiated (Na+) variant of your compound, while the unknown species at 223 could be an in source fragment (either protonated or sodiated) of your main component.
Hope this helps.
Mr. Sv,
The more recent methodological MS developments of methods for quantitative and 3D structural analysis, which allow us to determine analytes unambiguously can be found in the following review-article [1]. Therein, are presented the concepts which deterine how should be carried out quantification of MS intensity and the peak position, which have been described both theoretically and experimentally. Even operating with ultra-high resolving power, the accurate quantitative treatment of the MS outcomes is of paramount importance. The theoretical backgroun, why the latter statement is true one has deen detailed in the review mentioned above and reference [2].
[1] https://www.degruyter.com/view/j/revac.2019.38.issue-2/revac-2019-0003/revac-2019-0003.xml?format=INT
[2] https://www.sciencedirect.com/science/article/abs/pii/S0167732219306609
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