Mass Spectrometer Voltage Control for MRM Cycle Time
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Solution Overview
Problem
Conventional high-voltage power supply devices for mass spectrometers require longer times to decrease voltage levels, leading to increased cycle times and reduced detection sensitivity during simultaneous multi-component analyses, particularly in MRM measurements where rapid voltage changes are necessary.
Innovation Solution
A mass spectrometer system that includes an information collector and a measurement order determiner to organize and prioritize MRM transitions by their required voltage levels, allowing for quicker voltage changes by sorting measurements by absolute voltage values within each polarity group, thereby reducing settling times and improving data acquisition efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional high-voltage power supply devices are used with resistors connected in parallel to output terminals, then the device structure is simple, but the voltage decrease time is long which increases cycle time and reduces detection sensitivity
Solution Approach 1:
The patent changes the key parameter from resistance-based voltage control to capacitance-based voltage control. By connecting capacitors in parallel with the output terminals instead of (or in addition to) resistors, the voltage decrease time constant is controlled by the capacitor discharge characteristics rather than resistor discharge, enabling faster voltage transitions while maintaining circuit simplicity
Solution Approach 2:
The patent introduces dynamic control of the high voltage output by using switching elements (transistors or thyristors) to control the charging and discharging of capacitors. This allows the voltage to be dynamically adjusted between positive and negative polarities with controlled transition times, making the power supply responsive to the instantaneous ion polarity requirements
2Speed
If voltage switching speed is increased by using switch circuits with FET devices, then the polarity switching time is reduced, but the device complexity and circuit structure become more complicated
Solution Approach 1:
The patent changes the control parameter from direct FET switching to capacitor-based voltage storage and release. By using capacitors to store voltage and switching elements to control charge/discharge, the system achieves fast polarity switching without the complexity of sophisticated FET switch circuits, as the capacitor naturally provides smooth voltage transitions
Solution Approach 2:
The patent introduces capacitors as intermediary energy storage elements between the power supply and the ion source. These capacitors act as buffers that can quickly charge and discharge to provide the required voltage polarity changes, simplifying the overall control circuitry compared to direct FET switching approaches
3Productivity
If the cycle time for MRM measurements is reduced, then the detection sensitivity is improved, but the voltage settling time becomes insufficient leading to unstable measurements
Solution Approach 1:
The patent prepares the voltage in advance by pre-charging capacitors to the required voltage levels and polarities before measurement cycles begin. The capacitors are charged during idle periods or in parallel with measurement cycles, so when a voltage change is needed, the capacitor is already ready to discharge immediately, eliminating settling time issues
Solution Approach 2:
The patent maintains continuous voltage supply to the ion source through capacitor discharge during voltage transitions. Instead of interrupting the voltage supply during polarity switching, the capacitors continue to provide stable voltage output throughout the transition period, ensuring continuous and stable ionization without measurement interruptions
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 shortens the cycle time for MRM transitions, enhances ion detection sensitivity, and allows for more accurate quantitative determination by increasing the dwell time and number of data points collected during analysis.
Implementation Method 1
a positive voltage generation circuit and negative voltage generation circuit, each of which includes a DC-DC conversion circuit using an isolation transformer
Implementation Method 2
an ion source which employs an atmospheric pressure ionization method, such as an electrospray ionization (ESI)
Implementation Method 3
a mass separation unit for separating ions originating from a compound according to their mass-to-charge ratios
Data Source
AI summary
In a mass spectrometer according to the present invention, when MRM measurements for a plurality of MRM transitions need to be performed within one cycle, a measurement order rearranger determines an analysis sequence by sorting the measurement in ascending order of the absolute value of an optimum application voltage (an application voltage which gives the highest ionization efficiency) to the nozzle of the ESI probe. An analysis controller performs the analysis by controlling the high-voltage power source and other relevant units according to the determined analysis sequence. Since the voltage applied to the nozzle within one cycle has no period in which the voltage is changed in the decreasing direction with the same polarity, the cycle time becomes shorter than in a conventional device.