An online peak extraction algorithm for ion mobility spectrometry data

Dominik Kopczynski,Sven Rahmann

doi:10.1186/s13015-015-0045-5

Dominik Kopczynski, Sven Rahmann

Open Access

https://doi.org/10.1186/s13015-015-0045-5

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Abstract

Ion mobility (IM) spectrometry (IMS), coupled with multi-capillary columns (MCCs), has been gaining importance for biotechnological and medical applications because of its ability to detect and quantify volatile organic compounds (VOC) at low concentrations in the air or in exhaled breath at ambient pressure and temperature. Ongoing miniaturization of spectrometers creates the need for reliable data analysis on-the-fly in small embedded low-power devices. We present the first fully automated online peak extraction method for MCC/IMS measurements consisting of several thousand individual spectra. Each individual spectrum is processed as it arrives, removing the need to store the measurement before starting the analysis, as is currently the state of the art. Thus the analysis device can be an inexpensive low-power system such as the Raspberry Pi.The key idea is to extract one-dimensional peak models (with four parameters) from each spectrum and then merge these into peak chains and finally two-dimensional peak models. We describe the different algorithmic steps in detail and evaluate the online method against state-of-the-art peak extraction methods.

Highlights

Ion mobility (IM) spectrometry (IMS), coupled with multi-capillary columns (MCCs), MCC/IMS for short, has been gaining importance for biotechnological and medical applications
In contrast to other technologies, such as mass spectrometry coupled with gas chromatography (GC/MS), MCC/IMS works at ambient pressure and temperature
Data from MCC/IMS measurements In an MCC/IMS experiment, a mixture of several unknown volatile organic compounds (VOCs) is separated in two dimensions: first by retention time r in the MCC and second by drift time d through the IM spectrometer

Summary

Introduction

Ion mobility (IM) spectrometry (IMS), coupled with multi-capillary columns (MCCs), MCC/IMS for short, has been gaining importance for biotechnological and medical applications. Data from MCC/IMS measurements In an MCC/IMS experiment, a mixture of several unknown volatile organic compounds (VOCs) is separated in two dimensions: first by retention time r in the MCC (the time required for a particular compound to pass through the MCC) and second by drift time d through the IM spectrometer. Several components appear in each spectrum besides the peaks, namely the previously described RIP and the tailing described in Section ‘Data from MCC/IMS measurements’. As discussed in Section ‘Peak models’, the half-height width ω1/2 in retention time of a peak centered at retention time r can be described by an affine function ξ(r), Eq (3), and ω1/2 can be converted to the corresponding number of data points (window width).

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