Exercise 8 results


The performance was pretty good, not very astonishing for an open book exam with direct questions and multiple choice.. And the distribution looks as usual.

Difficult questions

The questions that gave the most wrong answers were the ones on the ‘true MS/MS’ character of MS-to-the-e. I admit that this might not become clear from a theoretical lecture – It will if you have concrete spectra and should derive information from them. But it is not a very important topic either.

True MS/MS selects one ion (even one isotope, usually) and this produces very straightforward, simple product ion spectra with typically no noise at all – even in the case of low signals and much background on the first MS level – and you can sort out interferences by displaying extracted ion chromatograms. If the chromatography does not fit the parent ion, it’s an interference. In the MS-to-the-e case, you always have interferences from all other parent ions and their fragments. You need to use spectrum subtraction and similar tricks, and it’s only working in the case of high signals and low interference.

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