I am having some issues understanding and processing LC-MS data. For each compound, there is a column for molecular weight, m/z, delta ppm and concentration per sample. There are many compounds that are false positives and need to be removed. I can't find any consistent method in filtering the compounds, I've been told that the molecular weight and m/z values need be similar, but I've heard anything from +/-1 to (m/z-molecular weight)/molecular weight *10^6
Noel W Davies Hi thank you for your response. I was given a list by a company who conducts LCMS. I was given a spreadsheet which included a column for Molecular Weight, m/z, RT (min), HMBD ID, Compound Name, Formula, Monoisotopic Mass, and Delta ppm. Each row is a different compound with concentrations corresponding to the sample. I was told that some of these compounds may not be properly identified, due to the Molecular Weight and m/z values being too dissimilar. I cannot find any clear methodology on how to check this, which is what I mentioned above ie. if the m/z value is +/- 1 of the known molecular weight of a compound, it has been incorrectly identified and should be removed from the list. Likewise, I have also seen calculations taking into account the ppm (in the spreadsheet they range anywhere from 1-20).