Ion Trap Voltage Control for Mass Spectrometer Sensitivity
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Solution Overview
Problem
The accumulation of ions in an ion trap can lead to space charge effects, reducing the efficiency of ion detection sensitivity and selectivity, as other ions outside the target mass range are unintentionally isolated due to changes in the electric field, resulting in decreased ion detection sensitivity and selectivity.
Innovation Solution
The mass spectrometer calculates the total ion accumulation before each period of accumulation, isolation, dissociation, and ejection, and adjusts the voltage conditions based on this calculation to correct for space charge effects, ensuring high-sensitivity analysis and high ion selectivity without altering the ion accumulation time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If ion accumulation time is increased to improve detection sensitivity, then more ions are accumulated in the ion trap, but space charge effects intensify causing unintentional isolation of non-target ions and reduced ion selectivity
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the RF voltage amplitude and supplemental AC voltage parameters based on the accumulated ion content. When ion content increases, the system modifies voltage parameters to compensate for space charge effects, maintaining both high sensitivity and selectivity without requiring shorter accumulation times
Solution Approach 2:
The system implements feedback by monitoring the ion content in the ion trap and using this information to adjust voltage parameters in real-time. The controller modifies RF and supplemental AC voltage based on detected ion levels, creating a closed-loop system that maintains optimal performance across varying ion accumulation conditions
2Ease of operation
If voltage parameters are kept constant during ion accumulation, then the system operation is simple, but space charge effects cause shifts in electric field and unintended isolation of ions outside target mass range
Solution Approach 1:
The patent applies dynamics by transitioning from static constant voltage parameters to dynamic time-varying voltage parameters. The RF voltage amplitude and supplemental AC voltage are continuously adjusted based on ion content, allowing the system to adapt to changing conditions while maintaining precise ion isolation accuracy
Solution Approach 2:
The system changes voltage parameters dynamically based on ion accumulation levels. The controller adjusts RF voltage amplitude and supplemental AC voltage parameters in response to ion content changes, preventing space charge-induced electric field shifts and maintaining accurate ion isolation
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 effectively mitigates space charge influences, enhancing ion detection sensitivity and selectivity by accurately isolating target ions and reducing the impact of space charge on voltage conditions, thereby improving the precision of mass spectrometry results.
Implementation Method 1
the three-dimensional quadrupole ion trap is able to stably accumulate ions having a specific mass-to-charge ratio in the ion trap by applying RF voltage to the ion trap
Implementation Method 2
by applying RF voltage to the ion trap
Implementation Method 3
only those ions of specific mass-to-charge ratio, which have specific frequency to oscillate resonantly by the supplemental AC voltage, are ejected from the ion trap
Implementation Method 4
the ions isolated by supplemental AC voltage are oscillated resonantly and collide with a bath gas inside the ion trap to induce dissociation of ions
Data Source
AI summary
A mass spectrometer capable of realizing a high-sensitivity ion analysis and a high ion selectivity performance. The mass spectrometer includes the ion source where ions are produced, the ion trap where ions are accumulated, isolated, dissociated, and ejected, the detector to detect ions to be detected, and the controller to control operations of the ion trap. It has the features that the total ion accumulation in or just before each period is calculated based on the result obtained from the mass spectrometry in the preceding period, and that in at least one out of all periods, the condition of voltage applied to the ion trap is corrected depending on the total ion accumulation. Compared to the related art, the mass spectrometer of the present invention provides much improved performance in analysis sensitivity and ion selectivity.