Mass Spectrometer Voltage Step Control
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Solution Overview
Problem
Conventional mass spectrometers face challenges in efficiently adjusting voltages applied to ion transport optical elements to maximize ion intensity while minimizing the time required for automatic adjustment, as the voltage step size must be small to find the optimal value, leading to prolonged measurement times.
Innovation Solution
The mass spectrometer adjusts the voltage step size based on the mass-to-charge ratio of the analyzed ions, increasing the step size with higher mass-to-charge ratios to find the optimal voltage value with minimal intensity drop, allowing precise identification of peak ion intensity without unnecessary measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the voltage step size is made small to find the optimal voltage value, then the measurement precision is improved, but the time required for automatic adjustment increases
Solution Approach 1:
The patent applies dynamics by making the voltage step size variable rather than fixed. The step size is dynamically adjusted based on the current voltage value and the shape of the ion intensity curve. When the system is far from the optimal voltage, larger steps are used to quickly approach the peak region. When near the optimal voltage, smaller steps are used to precisely locate the maximum ion intensity point. This dynamic adjustment resolves the contradiction between measurement precision and adjustment time.
Solution Approach 2:
The patent changes the parameter of voltage step size based on the analysis conditions, including the mass-to-charge ratio of ions and the current position on the ion intensity curve. By adapting the step size to these parameters, the system achieves both efficient searching (larger steps when far from optimum) and precise measurement (smaller steps near the peak), thereby resolving the time-precision tradeoff.
2Productivity
If the voltage step size is increased to reduce adjustment time, then the productivity is improved, but the measurement precision deteriorates
Solution Approach 1:
The system dynamically adjusts the voltage step size during the automatic tuning process. Initially, larger step sizes are used to quickly scan through the voltage range and approach the optimal region, improving productivity. As the system nears the optimal voltage (identified by the peak of the ion intensity bell-shaped curve), the step size automatically decreases to ensure precise localization of the maximum ion intensity, maintaining measurement precision.
Solution Approach 2:
The voltage search range is segmented into different regions: a coarse search region where large voltage steps are applied to quickly cover the range, and a fine search region near the optimal voltage where small steps are used for precise measurement. This segmentation allows the system to achieve both high productivity in the coarse region and high precision in the fine region.
Data Source
AI summary
The larger an m/z to be adjusted, the wider a peak width which represents change in intensity in relation to change in voltage. This allows voltage step size to be increased during a search for an optimum voltage without overlooking a maximum intensity. Thus, a relational expression which gives a narrow voltage step size for a low m/z and gives a wide voltage step size for a high m/z is prestored in a voltage step information storage unit (32), an optimum voltage adjustment controller (31) finds an optimum voltage step size for the m/z to be adjusted, during automatic voltage adjustment using the stored information, and controls a power supply unit 21 so as to change a voltage applied to a first ion guide (8) stepwise. Ion intensity obtained each time the applied voltage changes is determined, and a voltage value which gives a maximum ion intensity is found and stored in an optimum voltage information storage unit (33). Consequently, during automatic adjustment of a voltage applied to an ion transport optical element such as an ion guide, the time required for the adjustment can be reduced without overlooking an optimum voltage value which gives a maximum ion intensity.