Ion Population Control in Mass Spectrometer Optics
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Solution Overview
Problem
Existing ion trap mass spectrometers face challenges in optimizing ion population due to m/z-dependent ion transfer optics, leading to space charging and reduced sensitivity, particularly when transitioning between full-scan and data-dependent MS/MS or MSn experiments.
Innovation Solution
A method is introduced to adjust ion injection times based on mass-to-charge ratios, using a stacked-ring-ion-guide ion transport device with varying RF voltage amplitudes to optimize ion transmission, and incorporating a calibration factor to correct for differences in injection efficiencies between full-scan and data-dependent experiments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pre-scan is performed before each data-dependent experiment to calculate injection time, then ion population optimization is improved, but cycle time increases
Solution Approach 1:
The patent performs a pre-scan before each data-dependent experiment to measure ion flux and calculate the appropriate injection time. This preliminary measurement allows the system to optimize ion population for subsequent experiments while minimizing space charge effects. The pre-scan provides the necessary data to determine optimal injection parameters without requiring trial-and-error adjustments during the main experiment.
Solution Approach 2:
The system uses its own full-scan data to automatically determine injection times for subsequent data-dependent experiments. The ion flux measurements from the full scan are processed by the control system to calculate optimal injection parameters, eliminating the need for external calibration or manual intervention. This self-adjusting mechanism optimizes performance while adapting to changing sample conditions.
2Adaptability or versatility
If ion injection parameters are optimized for full-scan experiments with wide m/z range, then transmission across wide m/z range is improved, but transmission efficiency for specific precursor ions in data-dependent experiments decreases
Solution Approach 1:
The patent dynamically adjusts ion injection parameters based on the experiment type. For full-scan experiments, the system uses injection parameters optimized for wide m/z range coverage. For data-dependent experiments, the system calculates and applies modified injection parameters tailored to the specific precursor ion mass and desired transmission efficiency. This dynamic adaptation allows optimal performance for each experiment type without compromising the other.
Solution Approach 2:
The system applies different injection optimization strategies to different experimental contexts. Full-scan experiments receive broadband optimization for wide m/z range, while data-dependent experiments receive targeted optimization for specific precursor ions. The control system selectively applies appropriate injection parameters based on the experimental mode, ensuring local optimality for each application.
3Quantity of substance
If ion trap is overfilled to increase sensitivity, then sensitivity is improved, but space charge effects increase reducing resolution and mass accuracy
Solution Approach 1:
The patent implements a feedback mechanism where ion flux is measured during a pre-scan or full scan, and this measurement is used to calculate the optimal injection time for subsequent experiments. The system continuously monitors ion population characteristics and adjusts injection parameters accordingly, preventing overfilling while maintaining sensitivity. This closed-loop control ensures the ion trap operates at optimal capacity without excessive space charge effects.
Solution Approach 2:
The system changes injection parameters (specifically injection time and ion flux) based on measured ion population characteristics. By calculating optimal injection time from pre-scan data and adjusting injection parameters accordingly, the system maintains ion population within the optimal range that balances sensitivity with acceptable space charge effects, preventing both under-filling and overfilling conditions.
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 ensures more accurate ion population management, reducing space charging and enhancing sensitivity by optimizing ion transmission across a wide m/z range, thereby improving the overall performance of ion trap mass spectrometers.
Implementation Method 1
using a stacked-ring-ion-guide ion transport device with varying RF voltage amplitudes to optimize ion transmission
Data Source
AI summary
Methods for operating a mass spectrometer having at least one component having mass-dependent transmission, comprising: injecting a first sample of ions having a first mass range into an ion accumulator for a first injection time under first operating conditions suitable for optimizing transmission of ions of the first range; acquiring a full-scan mass spectrum of the first sample of ions; selecting ion species having a second mass range different than the first range; calculating a second injection time, the second injection time suitable for injecting a population of the selected ion species into the ion accumulator under second operating conditions suitable for optimizing transmission of ions of the second range; injecting a second sample of ions having the selected ion species into the ion accumulator for the second injection time under the second operating conditions; and acquiring a mass spectrum of ions derived from the selected ion species.