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September 24 - 28, 2006, 33rd FACSS 2006, Lake Buena Vista, FL, USA
Why is automating the determination of molecular ions so hard and how might it be used?
Mark Bayliss, Vitaly Lashin, Michel Hachey
Abstract
Molecular ion identification is the cornerstone of all MS1 data analyses for scientists across all sectors of mass spectrometry disciplines. Because molecular ion identification is a complex and time-consuming task, several chemometric approaches have been proposed to help accelerate the process. A number of highly accomplished algorithms have been created that make the problem more tractable by using reduction or removal of low frequency noise approaches, such as CODA from Windig et al. or MEND from Karger et al. However, while these extremely sensitive peak extraction algorithms simplify the analysis task, the output still requires a considerable amount of review by the scientist, which can be time-consuming. All of the extracted peaks, at a particular retention time, still need to be manually sorted and related to a particular eluting chemical component, and then the molecular ion needs to be picked out from amongst all the fragments, isotopes, and adducts. In fact, identification of the associated ions for an eluting component is an integral and necessary part of identifying and verifying the molecular ion identity.
A novel approach geared toward automatically grouping and identifying ions related to eluting components is presented. This approach builds on the CODA peak extraction algorithm in a way that overcomes the limitations imposed by the inherent noisy nature of MS1 data and that helps identify component ions. To limit the amount of algorithm parameter optimization carried on a per data set basis, a self-modeling approach was used to filter and automatically select optimal values. To determine the molecular ion for each eluting component, it was necessary to determine all ions within a particular retention time region using accurate retention times. The determination of molecular weight was made possible using as much information from the contributing ion clusters as possible, solving for classical adducts, multimers, and ion losses from the 12C molecular ion.
Download the poster in Adobe Acrobat format (131 Kb PDF file).
Relevant Products: MS Processor, MS Manager, MS Manager Suite
Relevant Solutions: Impurity and Degradant Studies, Metabolism Studies
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