XIC Peak Group Analysis for Retention Time Ambiguity in MS/MS
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Solution Overview
Problem
In complex samples, identifying and quantifying known compounds is challenging due to ambiguity in retention time caused by interference from other peaks with the same mass-to-charge ratio, especially when the expected retention time is unknown or varies significantly.
Innovation Solution
A system and method that uses a mass spectrometer coupled with a separation device to perform MS/MS scans with sequential mass window widths, spanning an entire mass range, and employs curve subtraction to accurately determine the retention time of known compounds, including their adducts, modified forms, or peptides, by comparing product ion spectra and calculating XIC peak groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional MS/MS scans with narrow precursor ion mass window width are used, then the measurement speed is maintained, but the measurement precision of retention time is degraded due to ambiguity in complex samples
Solution Approach 1:
The patent segments the mass-to-charge ratio range into multiple discrete windows (e.g., 10 windows across m/z 50-500). Instead of analyzing the entire mass range simultaneously with a narrow window, the system divides the range and sequentially analyzes each window, thereby improving retention time determination accuracy for each segment while maintaining overall system feasibility.
Solution Approach 2:
The patent performs preliminary data acquisition by collecting MS/MS spectra across multiple sequential mass windows before performing the actual compound identification. This preliminary collection of comprehensive mass spectral data allows for more accurate retention time determination through subsequent analysis of multiple product ions, resolving ambiguity in complex samples.
2Measurement precision
If sequential mass window widths are used to span entire mass range, then the measurement precision is improved, but the loss of time increases due to multiple scanning cycles
Solution Approach 1:
The patent implements periodic action by rapidly cycling through multiple sequential mass windows in a repeating sequence. The system acquires spectra from window 1, then window 2, continuing through all windows and repeating the cycle. This periodic scanning approach allows comprehensive mass range coverage while maintaining efficient data acquisition rates, improving identification accuracy without excessive time loss.
Solution Approach 2:
The patent maintains continuity of useful action by performing MS/MS scans continuously across all mass windows without interruption. Rather than stopping to reconfigure between windows, the system seamlessly transitions through each window in sequence, ensuring continuous data acquisition. This continuous operation minimizes idle time while gathering comprehensive spectral information for accurate compound identification.
3Reliability
If multiple product ions are monitored in complex mixtures, then the reliability of compound identification is improved, but the difficulty of detecting and measuring increases due to multiple peaks at different time intervals
Solution Approach 1:
The patent applies universality by using the same sequential mass window scanning approach for detecting multiple different product ions. The system doesn't require different measurement methods for each product ion; instead, it universally applies the multi-window MS/MS technique across all monitored ions. This unified approach simplifies the detection process while maintaining high reliability through comprehensive spectral data collection for each ion.
Solution Approach 2:
The patent uses feedback by comparing the observed retention times and spectral patterns of multiple product ions against expected values from spectral libraries. The system continuously refines compound identification by feedback from the consistency (or inconsistency) of retention times across different product ions. When multiple ions show consistent retention times matching expected values, identification reliability is confirmed; discrepancies trigger further analysis.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly improves the identification and quantification of known compounds in complex samples by resolving retention time ambiguity and verifying the presence of adducts, modified forms, or peptides, thereby enhancing the accuracy and reliability of compound detection.
Implementation Method 1
the eluting solvent is ionized and a series of mass spectra are obtained
Implementation Method 2
a mass spectrometer performs at each retention time of a plurality of retention times one or more mass spectrometry/mass spectrometry (MS/MS) scans
Implementation Method 3
A separation device separates a known compound and at least one adduct, modified form, or peptide of the known compound from a sample mixture
Data Source
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AI summary
A known compound and at least one adduct, modified form, or peptide of the known compound are separated from a sample mixture and analyzed. An XIC is calculated for each of M product ions of the known compound and L product ions of the at least one adduct, modified form, or peptide. A first XIC peak group is calculated from the M XICs and a second XIC peak group is calculated from the L XICs using curve subtraction. Representative first and second XIC peaks are selected for the two XIC peak groups. The retention of the second XIC peak is shifted by an expected retention time difference found from a database. The retention time of the first XIC peak is verified as the retention time of the known compound if the difference of the retention times of the first and second XIC peaks is within a threshold.