Sequential Windowed Precursor Ion Selection for Mass Spectrometry
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Solution Overview
Problem
Mass spectrometry experiments face challenges in identifying precursor ions due to contamination from fragments or adducts, which increase noise levels and reduce the number of compound identifications, especially in complex samples where traditional methods struggle with sensitivity and specificity.
Innovation Solution
Implementing a scanning sequential windowed precursor ion selection and mass analysis method that filters out fragments or adducts by scanning a precursor ion mass selection window across a mass range in overlapping steps, allowing for precise identification of precursor ions originating from an ion source device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precursor ion survey scan is performed to identify precursor ions, then the detection of compounds of interest can be conducted, but fragment ions and adduct ions contaminate the survey scan results, increasing noise and reducing identification accuracy
Solution Approach 1:
The mass range is divided into multiple sequential isolation windows that are scanned across the precursor ion mass range. Each window isolates a specific mass range, allowing systematic identification of precursor ions while excluding fragments and adducts that fall outside their respective isolation windows. This segmentation approach transforms a single contaminated survey scan into multiple targeted isolation events.
Solution Approach 2:
The system performs a preliminary precursor ion survey scan to identify candidate precursor ions, then uses this information to guide subsequent isolation and fragmentation events. The preliminary scan results are used to select which ions to isolate and fragment in later stages, ensuring that only genuine precursor ions (not fragments or adducts) are subjected to MS/MS analysis.
2Productivity
If traditional IDA methods are used to select precursor ions for MS/MS, then compound identification can be performed, but fragment and adduct ions are incorrectly selected, reducing the number of valid compound identifications
Solution Approach 1:
The mass range is divided into multiple sequential isolation windows that are scanned across the precursor ion mass range. Each window isolates a specific mass range, allowing systematic identification of precursor ions while excluding fragments and adducts that fall outside their respective isolation windows. This segmentation approach transforms a single contaminated survey scan into multiple targeted isolation events.
Solution Approach 2:
The system uses feedback from the precursor ion survey scan and isolation window scanning results to dynamically adjust which ions are selected for MS/MS fragmentation. By monitoring the mass spectra obtained from each isolation window and comparing against expected precursor ion characteristics, the system feedback-controls the selection process to prioritize genuine precursor ions over fragments and adducts.
3Adaptability or versatility
If the mass spectrometer scans a wide mass range in a single survey scan, then all potential precursor ions can be detected, but fragment and adduct ions within the range confound the identification
Solution Approach 1:
The mass range is divided into multiple sequential isolation windows that are scanned across the precursor ion mass range. Each window isolates a specific mass range, allowing systematic identification of precursor ions while excluding fragments and adducts that fall outside their respective isolation windows. This segmentation approach transforms a single contaminated survey scan into multiple targeted isolation events.
Solution Approach 2:
The system adds a temporal dimension to the mass analysis by sequentially scanning through multiple isolation windows across the mass range. Instead of attempting to analyze all masses simultaneously in a single survey scan, the system performs repeated isolation and analysis events in sequence, using time to resolve the overlap between different mass ranges and their associated fragments/adducts.
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 enhances the sensitivity and specificity of precursor ion identification, reducing noise and improving the accuracy of compound detection in complex samples by filtering out contaminants and allowing all precursor ions from the ion source to be visible to the mass spectrometer.
Implementation Method 1
a mass filter is instructed to filter an ion beam by scanning a precursor ion mass selection window across a precursor ion mass range of interest
Implementation Method 2
an ion source device is instructed to ionize and transform a sample or compounds of interest from the sample into an ion beam
Data Source
AI summary
A system is disclosed for identifying precursor ions originating from an ion source device. A mass filter filters an ion beam by using a series of overlapping precursor ion mass selection windows across the precursor ion mass range. A mass analyzer analyzes the precursor ions of each precursor ion mass selection window of the series, producing a plurality of precursor ion spectra for the precursor ion mass range. A precursor ion is selected from the spectra. The intensities for the selected precursor ion are retrieved from the spectra and a trace is produced that describes how the intensity of the selected precursor ion varies with the location of the precursor ion mass selection window. The selected precursor ion is identified as a precursor ion originating from the ion source device if the trace includes a nonzero intensity for the m/z value of the selected precursor ion.