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Topic: Cannot find spiked standards in the annotated compound list (Read 1243 times) previous topic - next topic

Cannot find spiked standards in the annotated compound list

Hello all, a noobie here.

I am trying to make sense of my LC-MS^n data. Before running my samples on the instrument, I spiked them with two internal standards (lidocaine and biochanin A). I preprocessed my files using the standard xcms pipeline, but I cannot find my standards in the rowData(results) file. I know what m/z and RT to expect, but the compounds that best correspond to these, differ in RT time by 20.33 and 0.248 seconds (respectively). This is a big difference, isn't it?

I then used m/z only search of compounds in MassBank using these data, and neither lidocaine not biochanin were identified as matches.

What should I do with all this? are the peak-picking parameters my problem? The parameters I used were chosen by IPO package using polled samples. How do I now that my tweaking them improved the situation rather than made it worse?