Centergram representation

The centergram representation is a superposition of the base peak profile (BPP) and a line graph representation of the peak list. The line graph is a Matlab stem plot with the peak centre in the x-axis and peak maximum intensity in the y-axis. The example bellow was obtained using the CE-TOFMS urine dataset. The peak list was obtained after the following transformation

1. myFinnee = myFinnee.filterDataset(1, 'RemoveNoise:5:5:100');
2. myFinnee = myFinnee.BaselineCorrection(2);
3. myFinnee = myFinnee.filterDataset(3, 'RemoveNoise:5:5:100');
4. myFinnee = myFinnee.doCentroid(4, 'LocalMax:2:0');
5. myPeakList = PeakList(myFinnee.Datasets{5}, 100, 0.1, 5);

The centergram representation is simply obtained using

myPeakList.Centergram

or after zooming in

The superposition of the stem plot with the BPP allows to easily notice coeluting species. Using the Data cursor, individual stem line can be selected allowing to attach to the graph a datatip with key FOMs. A new figure will also pop in with the corresponding PIP.

It should be noted, that while some lines should be aligned with maxima in the BPP, this is not always the case. As bellow, if two ions do not significantly differs in their m/z and are not baseline separated they may be concatenated into a single PIP.

In this particular example, this can be corrected using a smaller deltmz. However, this is not always the case.

myPeakList = PeakList(myFinnee.Datasets{5}, 100, 0.01, 5);

The centergram representation is particularly attractive to detect base peak ions even in very complex mixtures and with an extremely low separation. This is demonstrated bellow with the four lines that are indicated in the previous figure.

Reference

1. Introducing the concept of centergram. A new tool to squeeze data from separation techniques–mass spectrometry couplings

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