Predictive AGC for Hybrid Mass Spectrometers
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Solution Overview
Problem
Existing methods for controlling ion population in mass spectrometers, particularly in hybrid instruments, face inaccuracies due to varying isolation efficiencies across different mass analyzers, leading to incorrect estimation of ion flux during dependent scans.
Innovation Solution
Characterizing and parameterizing ion transfer efficiencies across mass spectrometer components allows for accurate prediction of ion flux by using intensity information from previous survey acquisitions, even when instrumental parameters differ between survey and dependent acquisitions, and accounting for 'mass spectrometric dark matter' that contributes to charge density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If predictive AGC uses intensity information from survey scan to estimate ion flux for dependent scans, then ion population control is simplified and duty cycle is increased, but isolation efficiency variations cause inaccurate ion flux estimation
Solution Approach 1:
The patent performs preliminary characterization of isolation efficiency for each mass analyzer before actual data acquisition. These pre-determined efficiency values are stored and applied during predictive AGC calculations to correct the ion flux estimates derived from survey scan intensities, thereby maintaining accuracy while enabling simplified predictive control.
Solution Approach 2:
The patent introduces isolation efficiency as an intermediary correction factor between the survey scan intensity measurement and the final ion flux estimation. This intermediary parameter accounts for the differences in transmission characteristics between mass analyzers, allowing accurate flux prediction even when switching between different analyzer types for survey and dependent scans.
2Productivity
If hybrid mass analyzer is used with different analyzers for survey and dependent scans, then duty cycle is increased, but isolation efficiency differences cause incorrect ion population prediction
Solution Approach 1:
The patent assigns specific isolation efficiency characteristics to each mass analyzer type (e.g., quadrupole, ion trap, TOF). When performing predictive AGC, the system selects the appropriate efficiency value based on which analyzer will be used for the dependent scan, thereby accounting for local differences in transmission properties between different analyzer components of the hybrid system.
Solution Approach 2:
The patent changes the operational parameter being controlled from raw intensity to corrected ion flux by applying analyzer-specific isolation efficiency factors. This parameter transformation allows the system to maintain reliable ion population predictions despite using different analyzer types for survey and dependent acquisitions with different transmission characteristics.
3Device complexity
If ion flux estimation does not account for isolation efficiency, then calculation is simpler and faster, but accumulation time prediction becomes inaccurate
Solution Approach 1:
The patent performs the complex isolation efficiency characterization in advance and stores the results for reuse. During actual predictive AGC operations, the system simply retrieves and applies these pre-determined efficiency values, maintaining fast and simple calculations while incorporating the necessary corrections for accurate accumulation time prediction.
Data Source
AI summary
A method for mass analyzing ions comprising a restricted range mass-to-charge (m/z) ratios comprising performing a survey mass analysis using a mass analyzer to measure a flux of ions having m/z ratios within said restricted range and performing a dependent mass analysis of an optimal quantity of ions having m/z ratios within said restricted range, said optimal quantity collected for a time period determined by the measured ion flux, CHARACTERIZED IN THAT: the time period is determined using a corrected ion flux that accounts for one or more of: (a) imperfect restriction of collected ions to the range of m/z ratios, (b) inclusion of ions within the range of m/z ratios that are undetected by the survey mass analysis, (c) different mass analyzers used for the dependent and survey mass analyses, and (d) different ion pathways used during dependent and the survey mass analyses.