Segmented Multipole Rod Lens for Mass Spectrometer Mode Switching
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Solution Overview
Problem
Conventional mass spectrometers face challenges in achieving high ejection efficiency and mass resolving power simultaneously, particularly when switching between linear trap and quadrupole mass filter operations, as longer trap lengths compromise ejection efficiency and longer rod lengths improve resolving power but are incompatible with dual operation.
Innovation Solution
The mass spectrometer employs a multipole rod lens with a second lens installed between its ends, allowing for voltage regulation to trap and eject ions in a section of the multipole rod lens, and to selectively pass ions by mass by controlling the voltage potential difference between the second lens and the multipole rod lens, enabling efficient switching between linear trap and quadrupole mass filter modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the multipole rod lens length is increased to improve mass resolving power in quadrupole mass filter mode, then the mass resolving power is improved, but the ejection efficiency deteriorates in linear trap mode
Solution Approach 1:
The multipole rod lens is divided into multiple sections along the axial direction, with each section independently controllable for ion trapping. The second lens is positioned between specific sections, allowing selective trapping in a shortened effective trap length while maintaining the full rod lens length for high resolving power. This segmentation enables the system to achieve both high ejection efficiency (by limiting trap length) and high mass resolving power (by maintaining full rod lens length)
Solution Approach 2:
The voltage applied to the second lens is dynamically regulated to switch between trapping mode and mass filtering mode. In linear trap mode, the second lens voltage creates a potential well that confines ions in a shortened trap section. In quadrupole mass filter mode, the voltage regulation eliminates the potential well, allowing ions to traverse the full rod lens length for high resolving power measurement
2Productivity
If the multipole rod lens length is shortened to improve ejection efficiency in linear trap mode, then the ejection efficiency is improved, but the mass resolving power deteriorates in quadrupole mass filter mode
Solution Approach 1:
The multipole rod lens is segmented into multiple axial sections with independent voltage control. The second lens is strategically positioned between sections to create a shortened trapping region when needed. The physical rod lens maintains its full length for high resolving power, while the effective trap length is segmented and controlled by the second lens voltage, enabling short trap length for high ejection efficiency without sacrificing the full rod lens length required for high mass resolving power
3Productivity
If the voltage to the second lens is regulated to trap ions in a section of the multipole rod lens, then the ejection efficiency is improved, but the ability to operate as a quadrupole mass filter deteriorates
Solution Approach 1:
The second lens voltage is dynamically regulated to switch between two operational states: In linear trap mode, a specific voltage creates a potential well that confines ions in a shortened trap section, improving ejection efficiency. In quadrupole mass filter mode, the voltage is adjusted to eliminate the potential well, allowing ions to traverse the full rod lens length for high resolving power measurement. This dynamic voltage regulation enables the system to adapt between modes without structural modification
Solution Approach 2:
The second lens serves multiple functions: it acts as a trapping electrode in linear trap mode by creating a potential well, and as a voltage control element in quadrupole mass filter mode by regulating the potential difference to enable or disable trapping. This multi-functionality allows a single device structure to achieve both high ejection efficiency and high mass resolving power through voltage regulation
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 configuration achieves high ejection efficiency and mass resolving power, improving the duty cycle by allowing operation as both a linear trap with low spatial ion spread and a quadrupole mass filter with enhanced resolving power, independent of trap length.
Implementation Method 1
A pseudoharmonic potential formed by a linear quadrupole RF field along the radial direction is utilized for mass separation
Implementation Method 2
A pseudoharmonic potential formed by a linear quadrupole RF field along the radial direction is utilized for mass separation
Implementation Method 3
Ions are then axially selectively ejected by a fringing field generated between the quadrupole rod lens and the exit lens
Implementation Method 4
a linear quadrupole RF field and a linear quadrupole DC field are combined at respectively appropriate intensities, and the quadrupole mass filter selectively passes only those ions with a specified mass to charge ratio
Implementation Method 5
specified ions can be excited along the radial direction by applying a supplemental AC field across an opposing pair of quadrupole rod lenses
Data Source
AI summary
A mass spectrometer that is switchable to operate as a linear trap or as a mass filter, and attaining both high ejection efficiency when operated as a linear trap and high mass resolving power when operated as a mass filter. A mass spectrometer includes an ion source for ionizing a sample, a linear trap quadrupole rod lens supplied with ionized ions, a trap electrode for forming a potential to trap the supplied ions between one end of the quadrupole lens and the other end, a control unit to regulate the trap lens voltage, and a mass analyzer or detector to detect ions ejected from the linear trap, and characterized in switching between an operation where the supplied ions are trapped in a section quadrupole rod lens and ejected by the controller unit regulating the trap electrode voltage; and an operation where ions are selective passed through according to their mass. The ejection efficiency when operated as an ion trap, and the mass resolving power when operated as a quadrupole mass filter are vastly improved compared to conventional methods.