Peak finder

Description

Following alignment, the resulting peak list may contain missing peaks as a product of a deficient peak detection or a mistake in the alignment of different peak lists.

The fact that one peak is missing after the alignment does not imply that the peak does not exits. In most cases it is present but was undetected by the previous algorithms.

This algorithm fills the gaps in the peak list when it is possible according with the parameters defined by the user. The most crucial parameters are "m/z tolerance" and "RT tolerance" which define the window where the algorithm should find the new peak. It is centered in the m/z average and retention time average of the source peak list. Once the best candidate is found inside the window, its intensity and its shape in RT direction is also checked.

It can also add a previous correction of the retention time in the case it is needed. It will change the position of the defined window depending on the prediction of a RT model created using all the already aligned peaks in each pair.

RT correction

When RT correction is applied, the algorithm is divided in two main steps. In the first step, one random sample is taken from the multiple peak list and is used as a master list. All the gaps of this master list are filled using all the others samples. For each pair of samples the algorithm creates a model of the retention time. In the second step the master list is used to fill the gaps of the rest of the samples, creating also a retention time model for each pair (as is is showed in the figure below).

Method parameters

Name suffix
Suffix to be added to the peak list name.
Intensity tolerance
This value sets the maximum allowed deviation from expected shape of a peak in chromatographic direction.
M/Z tolerance
This value sets the range, in terms of m/z, to search for possible peak in the raw data. Maximum allowed m/z difference.
Retention time tolerance type
Its value can be relative or absolute. The next parameters should be fill depending on the value chosen in this parameter.
Absolute RT tolerance
This value sets the range, in terms of retention time, to search for possible peak in the raw data. Maximum allowed absolute RT difference.
Relative RT tolerance
This value sets the range, in terms of retention time, to search for possible peak in the raw data. Maximum allowed relative RT difference.
RT Correction
When it is checked, correction of the retention time will be applied to avoid the problems caused by the deviation of the retention time between the samples.

New peak list showing the filled peaks with a yellow mark.