Tandem Time-of-Flight Mass Spectrometer Ion Gate Timing Optimization
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Solution Overview
Problem
In tandem time-of-flight mass spectrometry, especially with MALDI-TOFMS employing delayed extraction, the focal point differs slightly depending on the m/z value of ions, leading to varying ion mass resolution and requiring fine adjustments of instrumental conditions for each m/z value, which complicates optimal ion gate timing.
Innovation Solution
A method and apparatus that utilize a data table to store optimum delayed extraction conditions and ion gate open times for different mass-to-charge ratios, allowing for optimal ion gate timing across varying instrumental conditions by interpolating and approximating values using polynomial equations and partitioning subspaces, ensuring consistent mass resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If delayed extraction is employed in MALDI-TOFMS to converge ion energy distribution, then ion mass resolution is improved, but the focal point differs depending on m/z value requiring fine adjustments of instrumental conditions
Solution Approach 1:
The patent applies parameter changes by systematically varying delayed extraction conditions (extraction delay time and extraction voltage) and ion gate open time parameters to optimize mass resolution for different m/z values. A data table stores the relationship between these parameters and mass resolution, allowing the system to select optimal parameters based on the target ion's m/z value without manual fine-tuning.
Solution Approach 2:
The patent implements preliminary action by pre-measuring and storing optimal delayed extraction conditions and ion gate open times for multiple reference substances with different m/z values in a data table before actual analysis. This pre-characterization eliminates the need for time-consuming fine adjustments during operation, as the optimal parameters are already determined and stored for rapid retrieval.
2Measurement precision
If multiple turns in 8-shaped circulating orbit are used to lengthen total flight time, then mass resolution is improved, but lighter ions overtake heavier ions breaking the fundamental TOF-MS concept
Solution Approach 1:
The patent resolves the overtaking problem by transitioning from a planar 8-shaped circulating orbit to a three-dimensional spiral trajectory. By introducing a vertical dimension and using deflector electrodes to shift the starting and ending points of the closed trajectory in the vertical direction, the ion path becomes a spiral that prevents lighter ions from catching up to heavier ions, maintaining stable ion arrival order while achieving high mass resolution.
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 enables the ion gate to be set optimally at all times, maintaining high mass resolution across different m/z values without the need for frequent adjustments, improving the quality of product ion spectra.
Implementation Method 1
an ion source for ionizing a sample by irradiating it with pulsed laser light to generate ions
Implementation Method 2
acceleration means for extracting the generated ions in a pulsed manner and accelerating the ions by a pulsed accelerating voltage
Implementation Method 3
a first time-of-flight ion optical system permitting the accelerated ions to travel... a second time-of-flight ion optical system disposed behind the fragmentation means and permitting the product ions to travel
Data Source
AI summary
Tandem time-of-flight mass spectrometry method and apparatus permits an ion gate to be time set optimally at all times if the instrumental conditions are modified. Delayed extraction conditions for the mass-to-charge ratios of plural reference substances and optimum values of the time for which the ion gate is opened are measured and stored in a data table. Delayed extraction conditions and opening time of the ion gate which optimize the mass resolution at the mass-to-charge ratio of the desired precursor ions are found based on values stored in the table.