Tandem Mass Spectrometry Data Processing for Mixed Ion Identification
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Solution Overview
Problem
Conventional tandem mass spectrometry systems face challenges in accurately identifying compounds when multiple ion species with close mass-to-charge ratios are present, leading to mixed product-ion peaks in MS2 spectra, which complicates compound identification due to reduced sensitivity and accuracy in precursor-ion selection.
Innovation Solution
A tandem mass spectrometry data processing system that includes a product ion assignment determiner to identify the precursor ion origin of product ions by verifying composition formula consistency or mass defect similarity, and a data separator to reconstruct MSn spectrum data for each precursor ion, allowing for the separation of mixed product-ion peaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the mass-to-charge-ratio selection width for precursor ions is narrowed to improve compound identification accuracy, then measurement precision improves, but the amount of product ions decreases making it difficult to detect with sufficient sensitivity
Solution Approach 1:
The invention segments the mixed MSn spectrum data into multiple separate spectra, each corresponding to a different precursor ion. By performing composition formula estimation for multiple precursor ions and comparing them with product ion data, the system divides the mixed signal into distinct components, enabling accurate identification of each compound while maintaining sufficient product ion detection
Solution Approach 2:
The invention changes the approach from adjusting the mass-to-charge-ratio selection width to changing the data processing parameters. Instead of narrowing the selection window, the system uses composition formula estimation and mass defect comparison to differentiate between precursor ions, achieving high precision without sacrificing product ion quantity
2Quantity of substance
If multiple ion species with close mass-to-charge ratios are collectively selected as precursor ions, then the amount of product ions increases improving sensitivity, but the product-ion peaks become mixed reducing identification accuracy
Solution Approach 1:
The invention applies segmentation by dividing the mixed spectrum data into separate spectra for each precursor ion species. Through composition formula estimation and mass defect comparison, the system separates the contributions of different ion species, maintaining the benefits of collective selection while eliminating the identification accuracy problem
Solution Approach 2:
The invention introduces composition formula estimation and mass defect comparison as intermediary steps between precursor ion selection and spectrum analysis. These intermediaries enable the system to distinguish between different ion species even when they are collectively selected, resolving the mixing problem without sacrificing sensitivity
Data Source
AI summary
A composition formula of each precursor ion located on a measured mass spectrum is estimated from the m/z value of the precursor ion (S11). A composition formula of each product ion located on a measured MS/MS spectrum is estimated from the m/z value of the product ion (S11). For each product-ion peak, the assignment of the peak is determined by verifying consistency between the composition formula of the product ion and the composition formula of each of the precursor ions (S13-S14). Based on the assignment result, the MS/MS spectrum data are separated and an MS/MS spectrum for each precursor ion is created (S15-S16). In this manner, MS/MS spectra which respectively correspond to a plurality of compounds can be created from an MS/MS spectrum in which the product ions originating from those compounds are mixed, and those compounds can be identified.