Quadrupole Mass Spectrometer Auto-Tuning DC Bias Voltage
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Solution Overview
Problem
Conventional quadrupole mass spectrometers face reduced detection sensitivity at high scan speeds, especially for large mass-to-charge ratios, due to inadequate adjustment of ion-drawing bias voltage, which also affects mass resolution.
Innovation Solution
Incorporating a memory section to store bias voltage information relating scan speed and mass-to-charge ratio to optimal DC bias voltages, allowing for automatic tuning and adjustment during analysis to maximize detection sensitivity and maintain high mass resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the scan speed is raised to reduce analysis time, then productivity is improved, but the detection sensitivity deteriorates due to large voltage changes during ion passage
Solution Approach 1:
The patent applies dynamics by making the DC bias voltage adjustable and time-dependent. Instead of maintaining a constant DC bias voltage, the system dynamically changes the DC bias voltage in response to scan speed changes. This allows the voltage conditions to adapt to the ion passage time, ensuring that voltage changes during ion passage remain within acceptable limits even at high scan speeds, thereby maintaining detection sensitivity while improving productivity
Solution Approach 2:
The patent implements parameter changes by modifying the DC bias voltage parameter based on scan speed. The control section adjusts the DC bias voltage applied to the quadrupole mass filter according to the selected scan speed, ensuring optimal voltage conditions for each scanning scenario. This parameter adjustment compensates for the effects of high scan speeds on ion passage, maintaining measurement precision while enabling faster scanning
2Measurement precision
If the DC bias voltage is increased to improve detection sensitivity at high scan speeds, then detection sensitivity is improved, but mass resolution deteriorates
Solution Approach 1:
The system dynamically adjusts the DC bias voltage based on the operating conditions. Rather than using a fixed high voltage that would always compromise mass resolution, the control section applies higher DC bias voltage only when necessary (at high scan speeds) and adjusts it appropriately to balance detection sensitivity and mass resolution requirements
Solution Approach 2:
The patent changes the DC bias voltage parameter selectively based on scan speed conditions. The control section implements a strategy where the DC bias voltage is adjusted to optimize detection sensitivity at high scan speeds while maintaining mass resolution at lower scan speeds, achieving a balance between the two competing requirements through conditional parameter modification
3Ease of operation
If the ion-drawing bias voltage is kept constant to simplify operation, then ease of operation is maintained, but detection sensitivity deteriorates at high scan speeds
Solution Approach 1:
The system implements self-service by automatically adjusting the DC bias voltage based on the scan speed selected by the operator. The control section monitors the operating conditions and autonomously modifies the voltage parameters without requiring manual intervention, maintaining ease of operation while improving detection sensitivity through adaptive voltage control
Solution Approach 2:
The patent incorporates feedback mechanisms where the control section continuously monitors the scan speed and adjusts the DC bias voltage accordingly. This closed-loop control ensures that the voltage conditions remain optimal for the current operating parameters, maintaining detection sensitivity while keeping the operation simple for the user
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
Ensures high detection sensitivity across various scan speeds and mass ranges by optimizing the DC bias voltage, reducing the impact of scan speed on detection sensitivity and maintaining mass resolution, allowing for efficient analysis with minimal operator intervention.
Implementation Method 1
A voltage generated by superposing a direct-current (DC) voltage on a radio-frequency voltage is applied to each of the four electrodes of the quadrupole mass filter 3 so as to select ions in such a manner that an ion having a specific mass-to-charge ratio corresponding to the applied voltages is selectively allowed to pass through
Implementation Method 2
An ion-drawing bias voltage, which is a DC voltage, is commonly superposed on the ion-selecting voltages applied to the rod electrodes of the quadruple mass filter 3. This bias voltage creates an appropriate DC electric field in a space between the quadruple mass filter 3 and the ion optical system 2 in order to draw ions from that space into the quadrupole mass filter 3
Data Source
AI summary
A table (21) for relating an appropriate DC bias voltage to each of a plurality of selectable scan speeds is stored beforehand in an auto-tuning data memory section (20). In an auto-tuning operation, a controller (10) determines the DC bias voltage corresponding to each scan speed by referring to the table (21) and fixes the output of an ion-drawing voltage generator (13) at that voltage. Subsequently, while changing the voltages applied to relevant sections such as an ion optical system (2), the controller (10) finds voltage conditions under which the detection signal is maximized. The conditions thus found are stored in an auto-tuning result data (22). In an analysis of a target sample, a DC bias voltage corresponding to a scan speed specified by an operator is obtained from the DC bias voltage table (21), and the optimal conditions for this voltage are obtained from the auto-tuning result data (22). Based on these items of information, conditions for the scan measurement are determined. This method prevents the deterioration in detection sensitivity, which will otherwise take place if the scan measurement is performed at a high scan speed.